Citation
Proceedings

Material Information

Title:
Proceedings
Alternate Title:
Proceedings of the Soil and Crop Science Society of Florida
Alternate Title:
Soil and Crop Science Society of Florida proceedings
Abbreviated Title:
Proc.- Soil Crop Sci. Soc. Fla.
Creator:
Soil and Crop Science Society of Florida -- Meeting
Place of Publication:
Hollywood, Fla
Publisher:
Soil and Crop Science Society of Florida
Publication Date:
Frequency:
Annual
regular
Language:
English
Edition:
Volume 39, 1980
Physical Description:
48 volumes : illustrations, portraits ; 23-28 cm

Subjects

Subjects / Keywords:
Soil science -- Congresses ( lcsh )
Crop science -- Congresses ( lcsh )
Crop science ( fast )
Soil science ( fast )
Genre:
Conference papers and proceedings. ( fast )
serial ( sobekcm )
conference publication ( marcgt )

Notes

Citation/Reference:
Chemical abstracts
Dates or Sequential Designation:
Vol. 16 (1956)-v. 64 (2005).
General Note:
Some issues accompanied by CD-ROM.
Statement of Responsibility:
the Soil and Crop Science Society of Florida.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright, Soil and Crop Science Society of Florida. Permission granted to University of Florida to digitize and display this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Resource Identifier:
01489546 ( OCLC )
43013238 ( LCCN )
0096-4522 ( ISSN )
ocm01489546
020317058 ( Aleph )
Classification:
S590 .S65 ( lcc )
631.4062759 ( ddc )

Related Items

Preceded by:
Proceedings
Succeeded by:
Proceedings

Downloads

This item has the following downloads:

AA00067243_00024.pdf

00006.txt

00026.txt

00047.txt

00080.txt

00058.txt

00105.txt

00060.txt

00054.txt

00092.txt

00051.txt

00055.txt

00061.txt

00153.txt

00162.txt

00137.txt

00067.txt

00142.txt

00037.txt

00033.txt

00100.txt

00096.txt

00145.txt

00108.txt

00062.txt

00002.txt

00112.txt

00146.txt

00076.txt

00057.txt

00148.txt

00158.txt

00087.txt

00066.txt

00073.txt

00075.txt

00007.txt

00127.txt

00027.txt

00063.txt

00114.txt

00091.txt

00071.txt

00120.txt

00059.txt

00136.txt

00150.txt

00042.txt

00012.txt

00156.txt

00125.txt

00023.txt

00167.txt

00039.txt

00122.txt

00163.txt

00133.txt

00072.txt

00081.txt

00020.txt

00038.txt

00151.txt

00101.txt

00011.txt

00160.txt

00034.txt

00010.txt

00083.txt

00157.txt

00143.txt

00024.txt

00110.txt

00093.txt

00117.txt

00152.txt

00022.txt

00119.txt

00168.txt

00111.txt

00154.txt

00019.txt

00126.txt

00135.txt

00070.txt

00032.txt

00138.txt

00068.txt

00107.txt

00128.txt

00140.txt

00064.txt

00008.txt

00035.txt

00095.txt

00090.txt

00016.txt

00116.txt

00118.txt

00005.txt

00103.txt

00166.txt

00017.txt

00139.txt

00097.txt

AA00067243_00024_pdf.txt

00050.txt

00121.txt

00085.txt

00018.txt

00098.txt

00113.txt

00052.txt

00144.txt

00084.txt

00069.txt

00134.txt

00004.txt

00088.txt

00029.txt

00074.txt

00132.txt

00077.txt

00041.txt

00053.txt

00164.txt

00104.txt

00115.txt

00078.txt

00149.txt

00141.txt

00131.txt

00021.txt

00028.txt

00031.txt

00009.txt

00046.txt

00147.txt

00044.txt

00013.txt

00001.txt

00109.txt

00099.txt

00102.txt

00040.txt

00129.txt

00094.txt

00159.txt

00014.txt

00086.txt

00130.txt

00049.txt

00079.txt

00048.txt

00165.txt

00123.txt

00065.txt

00106.txt

00015.txt

00056.txt

00045.txt

00161.txt

00030.txt

00089.txt

00082.txt

00155.txt

00036.txt

00124.txt

00043.txt

00025.txt

00003.txt


Full Text
SOIL and CROP SCIENCE
SOCIETY of FLORIDA
PROCEEDINGS
VOLUME 39
1980
THIRTY-NINTH ANNUAL MEETING
BREVARD AGRICULTURAL CENTER
FRANK WOLFE'S BEACHSIDE MOTEL
COCOA BEACH, FLORIDA
OCTOBER 2-4, 1979




SOIL and CROP SCIENCE
SOCIETY of FLORIDA
PROCEEDINGS
VOLUME 39
1980
THIRTY-NINTH ANNUAL MEETING
BREVARD AGRICULTURAL CENTER
FRANK WOLFE'S BEACHSIDE MOTEL
COCOA BEACH, FLORIDA
OCTOBER 2-4, 1979


Conversion Factors for English and Metric Units
To convert
To convert
column 1
column 2
into column 2,
into column 1
multiply by Column 1
Column 2
multiply by
LENGTH
0.621
kilometer, km
mile, mi
1.609
1.094
meter, m
yard, yd
0.914
0.394
centimeter, cm
inch, in
2.54
AREA
0.386
kilometer2, km2
mile2, mi2
2.590
247.1
kilometer2, km2
acre, acre
0.00405
2.471
hectare, ha
acre, acre
0.405
VOLUME
0.00973
meter3, m3
acre-inch
102.8
3.532
hectoliter, hi
cubic foot, ft3
0.2832
2.838
hectoliter, hi
bushel, bu
0.352
0.0284
liter
bushel, bu
35.24
1.057
liter
quart (liquid), qt
0.946
MASS
1.102
ton (metric)
ton (English)
0.9072
2.205
quintal, q
hundredweight,
0.454
cwt (short)
2.205
kilogram, kg
pound, lb
0.454
0.035
gram, g
ounce (avdp), oz
28.35
PRESSURE
14.22
kg/cm2
lb/inch2, psi
0.0703
0.9678
kg/cm2
atmospheres, atm
1.033
0.9869
bar
atmospheres, atm
1.013
YIELD OR RATE
0.446
ton (metric)/hectare
ton (English)/acre
2.240
0.892
kg/ha
lb/acre
1.12
0.892
quintal/hectare
hundredweight/acre
1.12
0.87
hectoliter/ha, hl/ha
bu/acre
1.15
TEMPERATURE
\
Celsius, C
Fahrenheit, F
T (F
C 1+32
, -17.8
oo
0
32
/
20
68
100
212


1979 OFFICERS
President: D. W. Jones
Agronomy Department, IFAS
University of Florida
President-Elect: V. W. Carlisle
Soil Science Department, IFAS
University of Florida
Secretary-Treasurer: J. B. Sartain
Soil Science Department, IFAS,
University of Florida
Gainesville, Florida 32611
Directors:
O. C. Ruelke (1979)
Agronomy Department, IFAS,
University of Florida
P. H. Everett (1980)
ARC-IFAS,
University of Florida,
Immokalee, Florida
F. M. Rhoads (1981)
AREC-IFAS, University ol
Florida
Quincy, Florida
EDITORIAL BOARD
Editor: E. S. Horner
Agronomy Department, IFAS,
University of Florida,
Gainesville
Associate Editor:
C. C. Hortenstine
Soil Science Department, IFAS
Published annually by the Soil and Crop
Science Society of Florida. Membership
dues including subscription to annual pro
ceedings are $10.00 per year. At least one
author of a paper submitted for publica
tion in the Proceedings must be an active
or honorary member of the Society except
for invitational papers. Ordinarily, con
tributions shall have been presented at
annual meetings; exceptions must have
approval of the Executive Committee and
the Editorial Board. Contributions may be
(1) papers on original research or (2) in
vitational papers of a philosophical or re
view nature presented before general as
semblies or in symposia. A charge of
$10.00 per printed page in the Proceedings
will be billed to the agency the author
represents to help defray printing costs.
Members are limited to senior authorship
of one volunteer paper per volume; there
is no limit for junior authorships.
THE SOIL AND CROP SCIENCE SOCIETY OF FLORIDA
PROCEEDINGS
VOL. 39 CONTENTS 1980
Dedication
Honorary Life Member vi
SYMPOSIUM
Native Range Land, A Low Energy Grassland Resource Lewis L. Yarlett 1
The Role of Improved Forage Crops in Livestock Systems O. Charles Ruelke 3
Soil Fertility Management for Improved Pastures William G. Blue 5
Integrating Native Range and Pasture E. R. Felton 8
Properties of Representative Peninsular Florida Soils Used for Range and Pasture
Victor W. Carlisle 9
SOILS SEGTION
Fruit Yield of Florida Belle Strawberries as Affected by Rates of a
Resin Coated Fertilizer E. E. Albregts and C. M. Howard 14
Copper Nutrition of Cucumber (Cucumis sativus L.) as Influenced by Fertilizer
Placement, Phosphorus Rate, and Phosphorus Source
A. A. Navarro and S. J. Locascio 16
Nitrogen Losses from Urea, Ammonium Sulfate, and Ammonium
Nitrate Applications to a Slash Pine Plantation
D. B. Boomsma and W. L. Pritchett 19
Profile Distribution of Phosphate and Metals in a Forest Soil Amended with
Garbage Compost J. G. A. Fiskell and W. L. Pritchett 23
Evaporation Effects on Sprinkler Irrigation Efficiencies
Allen G. Smajstrla and Richard S. Hanson 28
Soil-Water Characteristics of Histosols as Related to Water Table Depth
G. S. Rahi and S. F. Shih 34
Major Land Resource Areas in Florida R. E. Caldwell 38
Sulfur Fertilization of Corn Seedlings C. C. Mitchell, Jr. and R. N. Gallaher 40
The Response of the Three Perennial Warm-Season Grasses to Fertilizer
Nitrogen on Eaugallie Fine Sand (Alfic Haplaquod) in Central Florida
W. G. Blue, C. L. Dantzman, and V. Impithuksa 44
Mobility and Extractability of Phosphorus Applied to the Surface of Tifway
Bermudagrass Turf J. B. Sartain 47
Growth Responses of Young Slash Pine to Site Preparation and Fertilization on
Poorly Drained Soils W. L. Pritchett and E. G. Flaig 51
Corn Response to Nitrogen and Phosphorus in a Florida Ultisol for Simulation of
Field Fertilization Techniques Used in El Salvador E. Jacome and W. G. Blue 55
Growth and Cadmium Uptake by Lettuce and Radish Fertilized with Cadmium, Zinc,
and Sewage Sludge Charles C. Hortenstine 58
Genesis of Acid Sulfate Soils S. C. Hodges and V. W. Carlisle 62
Application of Ground Penetrating Radar to Soil Survey
R. W. Johnson, R. Glaccum, and R. Wojtasinski 68
Soil Characteristics and Their Relationship to Growth of Needlerush
Charles L. Coultas and Orion J. Weber 73
CROPS SECTION
Effect of Metalaxyl Fungicide (CGA 48988) on Blue Mold and Black Shank of
Tobacco Tom Kucharek, E. B. Whitty and John Taylor 78
Legume Covercrop Trials in Citrus Groves Carl A. Anderson 80
Vegetation in Areas Stripmined for Phosphate
Robert M. Craig and Donald C. Smith 83
Winter Hardiness in Limpograss, Hemarthria altissima A. J. Oakes 86
Reaction of Stylosanthes hamata (L.) Taub. Indigenous to Southeast Florida to
Colletotrcihum gloeosporioides (Penz.) Sacc.
R. M. Sonoda and J. B. Brolmann 88
Effect of Nematicides and Application Methods on Sting Nematode Control,
Root Nodulation, and Yield of Soybeans H. L. Rhoades 90
Forage Production From Pearl Millet Following Rye and Ryegrass Fertilized
With Sulfur-Coated Urea L. S. Dunavin 92


Rates of Decline in Productivity of Florida Sugarcane
Jose Alvarez, Gerald Kidder, Thomas H. Spreen, and Donald R. Crane, Jr.
Soil Temperature Related to Water Table Depth S. F. Shih and G. /. Gascho
Evaluation of Various Stylosanthes Accessions in South Florida
J. B. Brolmann
Factors that Influence Rural Land Prices in Florida
John E. Reynolds and Devin L. Tower
Determination of Optimal Levels of Field Crops, Forages, and Beef Cattle
Enterprises J. Walter Prevatt, John E. Reynolds, and Bryan E. Melton
Responses of Two Pearl Millets Grown in vitro After Inoculation with Azospirillum
brasilense S. C. Schank, Rex L. Smith and Glen C. Weiser
A Comparison of Insect Pest Populations in Natural and Chemically Treated
Plots of Alfalfa With and Without Irrigation
D. R. Minnick and O. C. Ruelke
Effect of Age of Bahiagrass Sod on Succeeding Corn Crops
A. J. Norden, V. G. Perry, F. G. Martin, and J. NeSmith
Effect of Herbicides Applied to Corn on Subsequent Tomato, Pepper, and
Cucumber Crops P. H. Everett, R. S. Kalmbacher, C. Chambliss, and D. FI. Teem
Nutrient Metabolism and Quality of Corn and Sorghum Silages Made with Caged
Layer Manure M. F. Richter and R. S. Kalmbacher
Factors Affecting Hydrocyanic Acid Potential of Ona Stargrass
E. M. Hodges, M. F. Richter, and F. G. Martin
Influence of Fungicides, Nematicides, and Tobacco Cultivis on Yield Losses
Due to the Black Shank-Root Knot Disease Complex
J. R. Rich, J. T. Johnson, and G. E. Sanden
Economics of Irrigating Peanuts
Timothy D. Hewitt, Daniel W. Gorbet, and George O. Westberry
Blue Mold Incidence in Tobacco as Affected by Nitrogen Fertilization
IT. D. Smith, E. B. Whitty, and T. A. Kucharek
Endomycorrhizal Fungus Infection in Citrus Fibrous Roots of Trees with
and without Blight S. Nemec
Aeschynomene spp.: Distribution and Potential Use
Albert E. Kretschmer, Jr., and Robert C. Bullock
Flowering Dates and Freeze Ratings of Cool-Season Forage Crops
in North Florida A. R. Soffes and G. M. Prine
SOCIETY AFFAIRS
Minutes of the Business Meeting
Banquet
Secretary-Treasurers Report
Honorary Life Members
Sustaining Members 1978 .
95
98
102
104
108
112
115
118
122
125
127
131
135
140
141
145
153
156
156
158
158
158


DEDICATION
Nathan Gammon, Jr.
Nathan Gammon, Jr., was born June 22, 1914, in
Cheyenne, Wyoming. His early childhood was spent in
Helena, Montana, and his teenage years in Washing
ton, D.C.
He majored in chemistry at the University of Mary
land and was awarded a Bachelor of Science degree in
1956. Following graduation, he worked for two years
as an Assistant in Agronomy (Chemist) at the Uni
versity of Maryland and was awarded a Master of Sci
ence in the area of soil chemistry in 1959.
In the summer of 1958, he went to the Ohio Agri
cultural Experiment Station at Wooster, Ohio, as a
half-time Assistant in Corn Investigations and gradu
ate student at Ohio State University. He was awarded
the Doctor of Philosophy degree from that institution
in 1941 with a major in soils and minors in chemistry
and plant physiology.
After one more year of full-time research at Wooster,
he was commissioned an Ensign in the United States
Naval Reserve and served on active duty in the Bureau
of Ordnance, Pyrotechnic Section, until released from
active duty as a Lieutenant, senior grade in December,
1945. While on active duty in the Washington, D.C.
area, he took advantage of the opportunity to take post
doctorate courses in the U.S.D.A. Graduate School.
Dr. Gammon joined the University of Florida staff
in January of 1946 as Soil Chemist and Professor of
Soils, a position in which he was held in high regard
until his retirement as Professor Emeritus in 1979.
His research career may best be described as a love
for the scientific with a close eye for the practical.
Some of his early studies on the potassium require
ments for white clover and other legumes led to co
operative studies with Dr. Win. G. Blue which changed
the 0-14-14 fertilizer recommendations for legume
pasture to 0-10-20 and 0-10-50 ratios that more nearly
meet the plant requirements. He worked with Dr.
Gaylord M. Volk in establishing the need for nitrate
nitrogen for potatoes, supplied either as fertilizer or
by soil pH adjustment that would insure rapid nitrate
production from ammoniacal forms of nitrogen. Dr.
Volk was again his coworker in a study of molybdenum
deficiency of cauliflower and other crops.
Dr. Gammon has always had an eye for beauty,
hence one of his first publications from Gainesville
was on the effect of pH on camellia growth; his last
was on a nutritional problem associated with rose root
stocks. Likewise, his feeling that agriculture should care
for the inner man intensified his nutritional studies
on pecans, peaches, and other fruits. His many publica
tions in the area, as well as an intense personal interest,
have made him a recognized national authority in the
area of pecan nutrition. The Florida and the South
eastern Pecan Growers Associations count him as an
active member.
During the 1970s, he taught an undergraduate
course in soil chemistry and a graduate course in micro
nutrients. He also directed students in a number of
Master and Doctor of Philosophy programs. His teach
ing was characterized by stressing the relationship of
scientific truths to practical results and an insistence
on truth and accuracy always administered with kind
ness and compassion.
While serving as President of the Soil and Crop
Science Society of Florida, Dr. Gammon appointed the
first editor of the Proceedings. This new appointment
resulted in the publication of the 1955 Proceedings on
time and the publication of all back issues within the
next two years.
Dr. Gammon was elected a Fellow of the American
Association for the Advancement of Science in 1940.
He was honored in 1955 by best paper awards in both
the Soil Science Society of Florida and the Florida
State Horticultural Society. In addition to these three
societies, he was also a member of the American Chem
ical Society, the American Society of Agronomy, the
Soil Science Society of America, and the University of
Florida Athenaeum Club. A number of research and
professional societies also elected him to membership
including Sigma Xi, Alpha Chi Sigma, Phi Lambda
Upsilon, Gamma Alpha, Phi Epsilon Phi, and Gamma
Sigma Delta.
The Soil and Crop Science Society of Florida, in
recognition of his many contributions to soil and plant
science in Florida, both in teaching and research, as
well as his many years of service to the Society as an
active member and as Associate Editor of the Proceed
ings, is pleased to dedicate Volume 59 of its Proceed
ings to Dr. Nathan Gammon, Jr.


HONORARY LIFE MEMBER
Gordon Beverly Killinger
In recognition of his many contributions to agri
culture and to the success of this Society, Gordon
Beverly Killinger has been selected to honorary life
time membership in the Soil and Crop Science Society
of Florida.
Dr. Killinger was born December 31, 1908, at Elliot,
Iowa. He earned his Bachelor of Science degree in
1930, his Master of Science degree in 1931, and the
Doctor of Philosophy degree in 1933. All degrees were
awarded by Iowa State University. The major for his
terminal degree was Soil Fertility and the minors were
Chemistry and Soil Bacteriology. After completion of
his formal education, Dr. Killinger was employed by
Federal Land Bank of Omaha. In 1934, he joined the
Soil Conservation Service at Mankato, Kansas and
completed the first soil erosion and land use maps of
Kansas and South Dakota.
In 1936, Dr. Killinger joined the faculty of Clemson
College, where he developed and taught the first pas
tures course offered at that institution. He also taught
other courses in forage and cover crops. He came to the
University of Florida in 1941 where he served as Agron
omist and Professor of Agronomy until his retirement
in 1975.
A large portion of Dr. Killingers professional career
was spent in the development of improved pastures.
His influence on pasture improvement in the South has
been considerable and he has numerous publications
on related subjects. He was a member of the teams that
developed and released Pangolagrass and Pensacola
Bahiagrass, which currently account for more than 3
million acres of pasture in the southern United States.
He made significant contributions to forage improve
ment through the breeding and release of Argentine
bahiagrass and Floranna White sweetclover.
From 1955 to 1957, Dr. Killinger served as Agron
omy Advisor and developed a pasture and forage pro
gram in Costa Rica, under a Florida ICA-STICA con
tract. In this program, he helped introduce Pangola-
grass and Coastal bermudagrass along with Louisiana
white and Kenlancl reclclover, which became popular
forages in that country. For his contributions to that
countrys agriculture, Dr. Killinger received a Costa
Rican award for outstanding research and develop
ment.
Returning to the University of Florida in 1957, Dr.
Killinger was appointed to serve on the Southern
Regional Technical Committee for new crops. Most of
the remainder of his active research career was spent
in evaluating new crop plants.
Dr. Killinger made significant contributions in the
area of agronomic instruction. In addition to organiz
ing and teaching courses at Clemson University, he
taught the course in Pasture Science at the University
of Florida. The pattern of instruction that he devel
oped was adopted by subsequent teachers of that
course. Dr. Killinger directed the graduate programs
of three doctoral students in Agronomy, as well as four
students in a Master of Science program.
Many awards have been bestowed upon Dr.
Killinger for his numerous contributions, and he has
served in many professional organizations. He was
elected a Fellow in the American Society of Agronomy
in 1962. He served as President of the Southern Branch
of the American Society of Agronomy in 1966, as well
as President of the Soil and Crop Science Society of
Florida in 1967. In recognition of his service to agri
culture, this Society dedicated their Proceedings, Vol
ume 38, to him in 1978. Dr. Killinger was also Chair
man of the Southern Pasture and Forage Conference in
1958. He has held membership in the American Society
of Agronomy, Crop Science Society of America, Soil
and Crop Science Society of Florida, and Southern
Agronomy Workers Association, as well as Sigma Xi,
Gamma Sigma Delta, and Alpha Zeta.
Well-known nationally and internationally, Dr.
Killinger has responded generously to the demands
placed on him. He enjoys an outstanding reputation as
a pasture scientist.
For his many contributions to the improvement of
forage and pasture production as well as his service to
this Society, the membership of the Soil and Crop Sci
ence Society of Florida is pleased to elect Dr. Gordon
B. Killinger as honorary life member.


SYMPOSIUM
Native Range Land,
A Low Energy Grassland Resource
Lewis L. Yarlett1
The United States, with only 6 percent of the
worlds population, uses over one-third of the worlds
energy. One-hundred percent of the U.S. population
has, through the media of radio, tv, and the press,
been informed of the fossil fuel energy crisis. Grassland
agriculture in Florida has for the past decades utilized
abundant, inexpensive energy for the production of
livestock forage. The major percentage of production
has come from improved pasture programs, which has
required large inputs of both fossil fuels and labor.
Increased recognition of proper use and management
of the native range resource can materially reduce the
amount of energy required by the Florida cattle in
dustry.
Range management is both an art and a science
founded on ecological principles. It deals with the
management of native grasslands and understory vege
tation on grazeable forestland. A basic factor in range
ecology is plant succession, the process by which plants
succeed other plants. Cattle are very selective grazers.
The most palatable grasses are those that are readily
selected and are replaced by less desirable species. The
key that controls the process is the rancher or manager
who knows his vegetation and can manage these re
sources.
Range forage is a combination of native species in
cluding grasses, grass-likes, legumes, and other forbs.
In one sense of the word it is a crop. It is a crop that
can be successfully grown. Range forage can be suc
cessfully managed. Harvesting is no problem. Cattle
can efficiently and economically harvest range forage.
The growing, management, and harvesting can be done
with the lowest possible input of energy of any grass
land enterprize.
Beginning with the Arab boycott early in 1974,
shortages of fossil fuel energy were felt by all segments
of our economy. The availability of fossil fuels in the
future will be critical. Agriculture has been indicated
as one industry likely to receive some priority for
needed food production.
Current beef production in Florida during the past
25 to 30 years has used high inputs of fossil fuel. Large
acreages of native range were converted to pasture and
maintained. Many pastures in south Florida were de
signed for irrigation and water control. In the not too
distant future water for pasture irrigation may be pro
hibitive due both to cost as well as legislatively estab
lished priorities. Many warnings have been issued of a
serious water quality problem and shortage in several
areas in south Florida.
Any present-day attempt to analyze the exact energy
cost of a grassland management program, either pasture
or range, is likely to be outdated within weeks. It is
difficult to gather the required data, prepare a sum
mary, and publish before the entire price structure
changes.
i Biologist, Range Ecosystem Management, School of Forest
Resources and Conservation, Institute of Food and Agricultural
Sciences, University of Florida, Gainesville, Florida.
In 1973 gasoline cost approximately .$0.40/gal
($0.11/liter) and diesel fuel $0.20 to 0.25/gal ($0.06/
liter). Converting flatwoods range to irrigated pasture
cost approximately $60 to 70/acre ($150 to 170/ha) in
1973 with an annual operating expense of about $10/
acre ($25/ha) (Hipp, 1974). Present day prices indicate
establishment costs of $200/acre ($500/ha) or more.
The 1978 cost of a complete 16" x 1300' (40 cm x 400
m) well was $35,000.2
Unfortunately, the bottom line is that production
of forage from improved pastures remains at very much
the same level in 1980 as it was in 1973. Production
and maintenance costs mandate that a low energy
grassland program circumvent the use of fertilized grass
to produce hay or to maintain brood cows on pastures.
From an economic as well as from a physiological
standpoint, improved pastures have only a specific use.
Pastures are best utilized as a breeding ground and to
produce beef and not to maintain the cow.
The range resource is easily managed and a logical
alternative for the development of a low energy grass
land program in Florida. It has been estimated that
8.4 to over 12 million acres (3.4 to 4.8 million hectares)
have the potential for management to produce forage
for livestock and improved wildlife habitat. This in
cludes range, commercial, and non-commercial forest
lands. A basic fact must be recognized. Experiences of
commercial producers indicate that coordinated pro
grams utilizing both pastures and range resources are
successful.
Many species of grasses, grasslikes, legumes, and
other forbs are present and are able to withstand ex
tremes of wet and dry. The extremes of heat and cold
induce only natural functions of plant growth. Insects
and disease are practically unknown to curb growth or
production. Depending upon the degree of manage
ment applied, production of a native forage resource
is variable. Unmanaged flatwoods in poor condition
produce 600 to 1200 pounds of forage per acre (670 to
1,340 kg/ha), useable for 6 to 8 weeks (White, 1973).
This has been commonly termed wiregrass manage
ment. On the other side of the ledger, with planned
management, 2,000 to 8,000 pounds of air dry forage
per acre (2,240 to 9,000 kg/ha) is available for utiliza
tion over a period of 6 to 9 months. Successful pro
ducers, utilizing both pastures and range with a
planned grazing system, average 4 to 6 months on
range and 6 to 8 months on pasture. Four thousand
pounds per acre (4,500 kg/ha) green weight of creep
ing bluestem (Schizachyrium stoloniferum Nash)
has been produced in an 11-month period on ranches
where palmetto was being mechanically controlled
(Yarlett, 1965). An additional 1,500 pounds per acre
(1,700 kg/ha) was produced by other desirable species.
Current research at the Ona Research Center indicates
creeping bluestem as a major species following pal
metto control, and comparable levels of production
(Kalmbacher, 1979).
^Personal communication with producers.


2
Soil and Crop Science Society of Florida
Marsh ranges are the most productive. Production
from maidencane can be expected to produce as much
as 8,000 pounds per acre (9,000 kg/ha) air dry. Re
search by White (197S) indicated 9,900 pound per
acre (11,000 kg/ha), air dry following one full growing
season after several years of heavy grazing. Research
is continuing on the productive potential of fresh
marshes dominated by maidencane.
The comparative energy inputs to manage ranges
are few compared to those for managing improved
pastures (Figs. 1 and 2). Many energy costs recur an
nually on pasture and require high inputs of fossil
fuel. Fertilizer production is related to the current
shortages of natural gas needed to produce basic
nitrogenous fertilizer material. Many economists have
predicted a substantial increase in fertilizer costs the
next three years.
Energy requirements for range improvement and
management are not prohibitive in light of present day
costs. The following preliminary costs were obtained
from feed producers, ranchers, and contractors. Pal
metto control is required on most flatwood ranges to
obtain maximum production. A D-7 catapiller pulling
the heavy marden chopper averages 8.7 gals/hr (33
liters/hr) diesel fuel. At a cost of $1.0/gal ($0.26/liter)
this amounts to $3.48/acre ($8.60/ha) for fuel. This
cost will amortize at $0.71 per acre ($1.75/ha) over a
period of seven years at 10 percent interest. A web
plow, with a lower fuel consumption of 8 gals/hr (30
liters/hr) and covering 30 acres (12 ha) per 8 hour day
is reported to cost slightly less.
Supplementation is essential for the utilization of
native range forage (Terry, 1979). A 32% protein
liquid supplement with urea sold for $135/ton ($150/
metric ton) in December 1979. Average consumption
per 1,000 pound (450 kg) brood cow is estimated at
2 lb/day (0.91 kg). Supplementation for a 180-day
grazing period, October 1 to April 1, on bluestem range
equals a cost of $24 per cow. Supplementation may
well be the most profitable outlay in a range program
to utilize the high volume of forage produced from
well-managed ranges.
There are benefits to be obtained from a combina
tion range management-pasture program. Recovery
and growth of native species is fast. Results from man
aging flatwood and marsh ranges can be expected in
12 months. One high-producing commercial operation
initiated such a program in 195821 years ago. An
other began in 1963 and has operated successfully since
then. There are others, both large and small, that have
initiated programs using a minimum acreage of pasture
for breeding grounds and growing the calf up to
market age and weight. Other benefits may be listed as
follows:
(a) Contributes to higher conception rates when
cows are moved from range to green pasture in
the spring.
(b) Range experience and research indicates a
longer life span for brood cows.
(c) Pasture rotations with rests of 30 days or more
break the life cycle of some species of parasites.
(d) Good quality range is ideal for dry cows.
(e) Good range provides for emergency forage dur
ing extreme wet or dry periods.
(f) Increased benefits from wildlifeespecially quail
and turkey.
(g) Labor costs are lower on high quality ranges.
(h) Energy costs are reduced.
Fig. 1.Comparative energetics of an acre of improved pasture
for 1973-1979. Unquantified inputs and products are shown in
white for 1973 and in black for 1979. Forage production remains
essentially the same with possible slight reductions. (Adopted
from An Analysis of Cattle Ranching in the Kissimmee River
Basin. Ecoimpact Inc. 1976.)
Fig. 2.Comparative energetics of an acre of native range.
Unquantified inputs and products are shown in white for 1973
and black for 1979. (Adapted from: An Analysis of Cattle
Ranching in the Kissimmee River Basin. Ecoimpact Inc. 1976.)
SUMMARY
Large inputs of energy have been profitable in the
past, since improved pasture techniques and practices
were developed and recommended under low energy
costs of yseterday prices. Production of forages with a
minimum input of energy is now essential. Present
realities appear to preclude continued neglect of
underrated range resources. The economics of energy
appear to dictate that ranching in Florida be brought
into balance with low-energy production methods. The
cattle cycle appears to operate on a seven year cycle
with highs and lows of both numbers and prices. High
producing ranges will fit any place in that seven year
cycle.
Ranchers with a high percent of their land in im
proved pastures have narrowed their flexibility and
now depend on energy subsidies, and the relationships
between energy and fertilizer costs will have drastic
repercussions on cattlemen who maintain improved
pasture. Cattlemen now contemplating the conversion
of more native range to improved pasture would be


Proceedings, Volume 39, 1980
well advised to consider the future costs of fertilizers,
equipment, fuel, and labor compared to benefits from
well managed and productive ranges.
LITERATURE CITED
Anderson, C. L., and T. S. Hipp. 1974. Requirements and re
turns for 1000-cow beef herds of flatwood soils in Florida.
Coop. Ext. Ser., Univ. of Fla. Circular 385.
Kalmbacker, R. IS. 1979. Submitted manuscripts for publication.
J. Range Manage.
Terry, W. S. 1979. Nutritive value of some Florida range grasses.
3
Proceedings, annual meeting, Southern Section Society for
Range Management. Sarasota, Fla.
White, L. D. 1973. Native forage resources and their potential.
Range resources of the Southeastern U.S. American Society
Agronomy special publication No. 21. pp. 1-17.
. 1973. Ecosystem analysis of Paynes Prairie. School of
Forest Resources and Conservation. Research Report #24.
Inst, of Food and Agri. Sciences. Univ. of Fla.
Yarlett, L. L. 1965. Control of saw palmetto and recovery of
native grasses. J. Range Manage. 18:344-345.
. 1969. Creeping bluestem [Andropogon stolonifer
(Nash) Hitch.]. J. Range. Manage. 23:117-122.
The Role of Improved Forage Crops in Livestock Systems1
O. Charles Ruelke2
What has happened to land use and what can we
anticipate in the near future? From data published in
Agricultural Statistics 1978 (9), grassland pastures in
the United States decreased from 633 million acres in
1959 to 598 million in 1974, while cropland used for
pasture increased from 66 million acres to 83 million
acres in the same period of time. Since then, data
gathered for the AGUA Report (8) in 1974, and pro
jected for 1985, indicated that total acreage of grass
lands of Florida would decrease by four percent. The
greatest decrease would be in range pastures and wood
land pastures, while improved pastures were expected
to increase by 10 percent. Land area used for improved
pastures in Florida was estimated at 3.1 million acres
in 1974 and is projected to increase to 3.4 million by
1985 (8). Land use for production of hay and silage
was expected to increase 20 and 83 percent respectively,
by 1985. According to the best information available,
Florida is well along the way toward fulfilling these
projections.
How important are forages in livestock systems?
The value of cattle and calves on farms and ranches of
the U.S. on January 1, 1979, went up to $44.7 billion,
65% greater than a year earlier (10). In Florida, dur
ing 1978, 26.3% of total agricultural sales was from
livestock and livestock products (10). Because forages
make up a major part of the feed requirements of live
stock, the value of forages was estimated to exceed
$428.7 million in Florida during 1978.
What are improved forage crops and where do they
originate? Examples of improved forage crops date
back to the introduction of Dutch White Clover by the
early colonists from Europe in the 1600s. Since then
common bermudagrass from India, common bahiagrass
from Cuba, digitgrass and limpograss from Africa, as
well as many tropical legumes from Central and South
America and other tropical areas, are examples of
introduced improved forage species. However, from
these introductions a considerable amount of testing,
breeding, selection, hybridization and evaluation has
been necessary to find species which were adapted to
iSymposium presentation at Joint Session of Florida Chapter
American Society of Range Management and Soil & Crop Science
Society of Florida 39th Annual Meeting, October 2, 1979, at the
Brevard Agricultural Center, 1125 W. King Street (SR 520),
Cocoa, Florida.
2Professor of Agronomy, Department of Agronomy, University
of Florida, Gainesville, Florida 32611.
the widely variable environments found in the USA
and especially in Florida. Production and performance
data at various locations can be obtained from State
Agricultural Experiment Station Reports (3) and have
contributed significantly to the selection of the best
adapted species and cultivars. Because of the great
diversity of climate and soils in Florida, species suited
to one location may not be suitable to another. Specif
ically, climate in North and Northwest Florida may be
characterized as temperate as a result of the cold fronts
and frequent periods when temperatures may remain
below freezing for more than a day at a time. Likewise,
many areas along the lower East and West coast of
Florida have more sub-tropical climate where frost may
not occur for periods of years.
Rainfall may vary from less than 40 inches per year
to over 60 inches per year with North and South Flor
ida having generally more rainfall, and Central Florida
less rainfall.
Soils of Florida also vary from the most productive
organic muck soils to almost completely sterile beach
sand. Obviously, the species and varieties of improved
forages will greatly differ from one location to another.
What then are the basic criteria necessary for select
ing improved forage species and cultivars for a specific
location? Probably temperature, extremes and dura
tions, should be considered first in selecting improved
forages species for an area because they have a com
manding effect on the production and quality of
forage. Because there is little we can do to control the
temperature, we must resort to species which perform
best under the prevailing temperatures.
Within any location in an area, moisture is prob
ably our second consideration. Although we cannot
stop rainfall we can add water by irrigation, if an
adequate supply of water is available.
Likewise, soil fertility ranks next in importance in
selecting an improved forage species for a specific site.
Fortunately, as a result of soil testing and previous ex
perience, it is possible to determine if and what soil
amendments can and must be used in order to estab
lish a specific improved forage crop. For example,
alfalfa and sweetclover require a pH range of 6.5-7.0
and a minimal CaO and MgO of 1200 and 100 Ibs/A
(1344 and 112 kg/ha) respectively, while true clovers
require pH 6.0-7.0 with CaO and MgO levels of 900
and 100 Ibs/A (1008 and 112 kg/ha) respectively.
Forage grasses require pH 5.5-6.5 with CaO and MgO


4
Soil and Crop Science Society of Florida
levels of 600 and 100 Ibs/A (672 and 112 kg/ha) re
spectively (11). Medium levels of P205 and KoO re
quired for improved forages on sandy soils of Florida
range from 81-140 lbs/A (91-157 kg/ha) and 91-150
lbs/A (102-168 kg/ha) respectively (12).
Will it pay to establish and produce improved for
ages? Numerous studies throughout the USA have re
searched this question. In Florida, the results from two
major independent studies (4, 5, 6, and 7) have shown
that improved grass-clover pastures greatly increased
the percentage calf crop, percentage of calves weaned,
calf weaning weights, calf grades, price per pound,
pounds of calf weight per cow and pounds of calf per
acre over that produced as straight grass alone or on
present native vegetation. As population increases,
natural grassland acreages decrease and taxation con
tinues to increase, it will be necessary to shift from an
extensive to a more intensive type of land use and man
agement. Although costs of inputs continue to increase
on both unimproved and improved grasslands, in
creased pressure from land use and increased return
per dollar invested in improvement will most likely
come from the improved forages.
What basic principles should be observed in man
agement of improved forage crops? The management
we apply to improved forages differs with the species,
growth habit, and stage of growth. Generally, grasses
like bahiagrass, carpetgrass, St. Augustine grass, and
legumes like white clover and subclover can be con
tinuously close grazed or harvested in order to get the
major portion of the forage available without severe
reduction in regrowth or stands. Grasses such as cool
season cereals (like oats or rye), warm season annuals
(like pearl millet and sorghums), and some perennial
erect tall growth grasses (like limpograss or napier-
grass), must be allowed to acumlate substantial
amounts of topgrowth before grazed or harvested fol
lowed by a sufficient rest period for regrowth. For these
species, and many of the erect winter and summer
legumes, rotational grazing is required in order to
achieve full yield potential and satisfactory persistence.
Deferring grazing, or harvesting, is extremely impor
tant while new plantings are getting established as well
as being a means of stockpiling forage during periods
of abundance (such as during the late summer), for
periods of shortages during the fall and early winter.
High quality forage like rye, ryegrass, or clover can be
used to supplement poor quality frosted bahiagrass or
native grasses. However, you must plan ahead to supply
your needs.
What basic principles should be observed in fer
tilization of improved forage crops? Before you estab
lish improved forage crops there must be a need for
the forage. If there is a need for the forage you must
provide the minimum fertilizer requirement of that
forage crop. You cannot make something out of noth
ing and forage crops cannot produce high yields of
quality forage without sufficient amounts of the es
sential elements. Fertilize forage crops when and where
the forage is needed. The optimum rate will be deter
mined by the dollars in forage value returned per
dollar spent for fertilizer on a specific species on a
specific location. Improved forage species are bred and
selected for increased efficiency in returning more for
age per dollar spent for production. When growing
legumes with grasses one can generally fertilize to favor
the legume (like clover) and the grass (like bahiagrass)
will take care of itself.
What role have unproved forages played in the in
crease in liveweiglit gains of forage feed cattle on the
sandy soils of southeastern USA? In a recent thought-
provoking article by Burton (2) he pointed out that, in
1860, cattle on native range averaged 4-8 pounds of
liveweight gain per acre (4.5-9 kg/ha) per year, while
in 1930 gains on common bermudagrass were 80 #/A
(90 kg/ha). In 1970 gains on Coastal bermudagrass
with 140 #/A (156 kg/ha) of N plus P and K were
485 #/A/yr (543 kg/ha). Further genetic improve
ment resulted in Coastcross-1 bermudagrass which
with 140 #/A (156 kg/ha) of N plus P and K, pro
duced 745 #/A/yr (834 kg/ha) of liveweight gain.
Today fertilized Coastcross-1 grazed with rye or rye
grass grazed has resulted in 1000 #/A/yr (1120 kg/ha)
gains in tests in Georgia. With a 12-month growing
season on fertilized organic soils in South Florida, beef
gains of over 2000 lbs/A (2290 kg/ha) have been re
ported for seven consecutive years (1).
In the future, with twelve months of the year pro
ducing improved forages, supplemented with addi
tional sources of feeds which are readily accessable,
fed to hybrid animals with stimulated appetites, is it
¡possible to produce 6000 # (6720 kg/ha) of beef/year
on one acre of land?
SELECTED LITERATURE CITED
1. Bair, R. A., and R. W. Kidder. 1946. Pasture investigations
on the peat and muck soils o£ the Everglades. Fla. Agr. Expt.
Sta. An. Rpt. pp. 180-181.
2. Burton, G. W. 1972. Can the South become the worlds great
est grassland? Prog. Farmer. 87:(3), pp. 22-24.
3. Dean, C. E. 1979. Florida field and forage crop variety re
port-1978. Agron. Res. Rpt. AG 79-5, IFAS Agr. Exp. Sta.
and Coop. Ext. Serv., Univ. of Fla., Gainesville, Fla. 90 p.
4. Roger, M., et al. 1961. Beef production, soil and forage
analysis, and economic returns from eight pasture programs
in North Central Florida. Fla. Agr. Exp. Sta. IFAS Bull.
631 (t) 76 p.
5. Roger, M., et al. 1970. Production response and economic
returns from five pasture programs in North Central Florida.
Fla. Agr. Exp. Sta. IFAS Bull. 740(t) 45 p.
6. Roger, M. 1977. Pasture programs and beef cattle breeding
systems for beef production in North Central Florida. Fla.
Agr. Exp. Sta. IFAS Bull. 789(t) 47 p.
7. Peacock, F. M., et al. 1976. Forage systems, beef production,
and economic evaluations, South Florida. Fla. Agr. Exp. Sta.
Bull. 783(t) 14 p.
8. Pierce, J. B. 1975. Agricultural growth in an urban age.
Institute of Food and Agricultural Sciences. Univ. of Fla.
230 p.
9. U.S.D.A. 1978. Agricultural statistics 1978. U.S. Govt. Print
ing Office, Washington, D.C. 605 pp.
10. U.S.D.A. 1979. Florida cash receipts from farming. Fla. Crop
and Livestock Reporting Service USDA, Fla. Dept, of Agri.
and Univ. of Fla. Agri. Exp. Sta. 2 p.
11. Whitty, E. B., et al. 1977. Liming for production of field and
forage crops. Agronomy Facts:69 Fla. Coop. Ext. Serv. IFAS,
Univ. of Fla. 4 p.
12. Whitty, E. B., et al. 1977. Fertilization of field and forage
crops. Agronomy Facts:70 Fla. Coop. Ext. Serv. IFAS, Univ.
of Fla. 13 p.


Proceedings, Volume 39, 1980
5
Soil Fertility Management for Improved Pastures1
William G. Blue2
ABSTRACT
Nutrient requirements for intensive forage crop
production are similar to those for soybean and corn.
On Floridas acid, infertile mineral soils, judicious
liming and micronutrient fertilization should precede
application of macronutrients because of the potential
for A1 toxicity, Mg deficiency, micronutrient deficien
cies, and losses of macronutrients through leaching.
Forage production and N content of white clover-
grasses without fertilizer N have been comparable to
those from perennial grasses fertilized with 224 to 448
kg of N/ha annually. Beef production from legume-
grass pastures generally exceeded that from grass pas
tures at N rates through 134 kg/ha/year. The po
tential for substitution of symbiotically-fixed N by
legumes for fertilizer N was emphasized. Lime and fer
tilizer costs per kg of beef, at current prices, are $0.51
for the grass and for the legume-grass pasture, less than
$0.18. For successful production of legume-grass pas
tures, management must be more precise and consistent
than for grass pasture. Soil acidity must be corrected
by liming, micronutrient levels must be maintained,
and P and K must be applied at least annually.
Additional Index Words: Lime, Micronutrients,
Nitrogen, Legumes, Fertilizer costs, Beef production,
White clover, Trifolium repens L.
Floridas mineral soils are derived from relatively
coarse-textured, highly weathered materials. Most of
the virgin soils are acid and extremely infertile. Toxic
quantities of soil solution A1 may be a problem and
deficiencies of N, P, and K are common. Calcium, Mg,
and S, and one or more of the micronutrientsFe, Mn,
Zn, Cu, B, and Momay be deficient at or soon after
initiation of cultivation and cropping.
In considering the potential for production of
forage and cattle on these soils, one needs to under
stand that their productive capacity was very low in the
virgin condition. Protein, energy, and essential in
organic nutrients in forages from these soils were de
ficient for cattle. While some of the improved forage
plants, notably some of the grasses, will survive under
minimal levels of nutrition, intensive forage produc
tion requires nutrient levels similar to those required
by agronomic crops (Table 1).
For sustained production on most of our mineral
soils, the soil as a source of nutrients, without lime and
fertilizers, can almost be ignored. Exceptions are N, S,
and some of the micronutrients. Small amounts of N
and S are mineralized from soil organic matter, and
some of both are brought down by rain from con
taminants in the air. Small additional amounts of N
appear to be fixed by blue-green algae and hetero-
trophic microorganisms. Some soils have reasonable
supplies of micronutrients, but for intensive produc-
iFlorida Agricultural Experiment Stations Journal Series No.
2249.
^Professor (Soil Chemistry and Fertility), Soil Science Depart
ment, Florida Agricultural Experiment Station, Gainesville, FL
32611.
TABLE 1.Nutrient contents of soybean, corn, and Pensacola
BAHIACRASS.
Crop
Soybeans! Corn:|: P. bahiagrassjj
Nutrient (3,020 kg/ha) (9,410 kg/ha) (11,200 kg/ha)
Nutrient contents of above-ground portion, kg/ha
Nitrogen (N)
448
190
174
Phosphorus (P)
45
39
26
Potassium (K.)
280
196
112
Calcium (Ca)
101
40
56
Magnesium (Mg)
65
44
45
Sulfur (S)
28
21
34
Iron (Fe)
2.6
2.1
0.9
Manganese (Mn)
0.7
0.3
0.2
Zinc (Zn)
0.4
0.3
0.2
Copper (Cu)
0.1
0.1
0.1
Boron (B)
0.1
0.2
0.2
Molybdenum (Mo)
0.01
0.01
0.01
'¡'Nitrogen in soybean is obtained primarily by symbiotic fixa
tion. Data were taken from Smith, Hutton, and Robertson (1968).
Data were taken from Barber and Olson (1968).
{¡Data were taken from Blue (1971).
tion systems, these usually require supplementation.
By far the largest quantities of nutrients must be sup
plied through lime and fertilizers.
The costs of these nutrients have increased mark
edly in the 1970s as a consequence of increased energy
costs. Current costs of fertilizers necessary to supply the
nutrients in Pensacola bahiagrass (Paspalum notatum
Flugge) forage at a production level of 11.2 metric
tons/ha (5 tons/acre) are shown in Table 2. Nutrient
contents were determined in harvested forages. Nutri
ent requirements of other improved grasses do not vary
appreciably from those for bahiagrass. Because ade
quate lime of the correct kind to maintain the opti
mum pH and Ca and Mg balance is relatively inex
pensive compared with the macronutrientsN, P, and
Kcorrect liming must have the highest priority. The
TABLE 2.Nutrient contents of Pensacola bahiagrass and
COSTS of lime and fertilizers required to supply these nutrients.
Nutrient
Quantity!
Cost!
kg/ha
$/ha
Nitrogen
174
124
Phosphorus
26
30
Potassium
112
30
Calcium
56 )
Magnesium
45 f
7.4
Sulfur
34

Iron
0.9
Manganese
0.2 'i
Zinc
0.2 /
Copper
0.1 [
2.5
Boron
0.2 (
Molybdenum
0.01 \
fBased on 11.2 metric tons/ha (5 tons/acre) oven-dry forage
yield. Fertilizer nutrients required exceed plant contents because
of nutrient leaching and other loss mechanisms. Prices were
calculated on basis of USDA Publication FS9, 1979 Fertilizer
Situation, Oct. 15, 1978. These prices will depend on fertilizer
formulation, quantity purchased, and other services provided by
the fertilizer dealer.


6
Soil and Crop Science Society of Florida
cost of micronutrients is also relatively small and these
should be applied initially to correct potential deficien
cies.
FERTILIZER N FOR GRASS PASTURE
Nitrogen, which is required in largest quantity and
at highest cost, is the driving force for forage produc
tion. Requirements for other nutrients are propor
tional to the supply of N. Pensacola bahiagrass forage
production in response to rates of fertilizer N on a
Spodosol (poorly drained flatwoods soil) and an
Entisol (well-drained, deep sandy soil) are shown in
Fig. 1. Growth response was linear through the 224
kg/ha N rate on both soils. The data should apply well
to soil-plant systems where hay is harvested. There is
some recycling of all nutrients under grazing, but the
magnitude of N reutilization has not been established.
Total forage production from the Spodosol varied
from 120 kg/ha for each kg of N at the current average
N fertilization rate of 45 kg/ha/year to 34 kg for each
kg of N at the 448-kg/ha N rate. Dry matter for each
kg of N from the Entisol varied from 77 to 28 kg for
N rates from 0 to 448 kg/ha/year (Table 3). The
seasonal distribution of grass forage production varies
in different parts of the state due to temperature varia
tions and soil types, particularly as related to moisture
supply. Thus, grass forage production will occur over
Fig. 1.Growth Response of Pensacola bahiagrass to fertilizer
nitrogen on a Spodosol (poorly drained flatwoods) and on an
Entisol (well-drained ridge).
TABLE 3.Pensacola bahiagrass growth response to fertilizer
NITROGEN.
N
applied
Spodosol
Entisol
Forage yields
Forage yields
kg/ha
kg/ha
per kg of N
kg/ha
per kg of N
0
2,950

1,530

45
4,780
120
3,080
77
112
7,290
73
5,170
52
224
10,790
54
8,030
40
336
13,430
45
10,100
34
448
15,220
38
11,390
28
approximately 6 to 8 months on the Spodosol, but
usually for not more than 4 or 5 months on the Entisol
due to location in the state and drought conditions in
the spring. With judicious management, grazing can be
extended for 2 additional months during the fall for
both soils by utilizing mature forages. However, some
supplemental foragehay or silageis required to
maintain animals in suitable condition for reproduc
tion and calf growth, both of which are required for
intensive animal production.
FORAGE REQUIREMENTS FOR BEEF CATTLE
Forage and nutrient requirements for cattle vary
with age and expected performance. However, an
average value for forage is 9.1 kg/animal/day; the an
nual requirement would be 3,320 kg/animal. There is
some wasted forage from grazing, perhaps as much as
30% under intensive forage production (Roger et al.,
1961). Thus, 1 ha of grass on the Spodosol fertilized
with 224 kg of N/year (Table 3) would produce
enough forage for three animals. Production would be
substantially less on the Entisol. Even with this level of
forage production, provision must be made for supple
mental grazing or feeding. Data from the Beef Re
search Unit, University of Florida, Gainesville indi
cate that sufficient corn silage for supplemental feed
ing of one animal can be produced on an additional
0.05 ha (Roger et ah, 1970). If the pasture were fer
tilized with only 45 kg of N/ha/year, forage produc
tion per ha would be substantially less and carrying
capacity would be reduced accordingly. Furthermore,
reproduction of cattle was a consistent problem with
grass pastures on Spodosols at the Beef Research Unit
(Roger et ah, 1961) regardless of fertilization rate even
though animals were supplemented with protein.
Forage and animal production under grazing are
shown for grass pastures on Spodosols at the Beef Re
search Unit (Table 4). Forage production was in
creased markedly by fertilization; however, weaning
percentages were relatively low. Beef (calf) production
per cow was relatively constant but production per
acre was increased. Fertilizer costs at present prices are
high in relation to the value of beef produced.
LEGUME-GRASS PASTURES
A viable alternative to grass with N fertilizer is
legume-grass pasture. Legumes are capable of fixation
of atmospheric N through symbiosis with Rhizobium
bacteria. Legumes include those which grow well dur
ing the cool season and others which grow during the
TABLE 4.Production performance of cows on grass pastures
on Spodosols, Beef Research Unit.!
Fertilization
Annual
forage
production
Weaning
%
Beef production
N
P
K
Per ha
Per cow
kg/ha/year
kg/ha
kg
38
9
9
5,220
63
111
120
76
18
18
7,440
64
151
123
134
36
36
9,630
66
226
123
tGrasses were Pensacola bahiagrass, Pangla digitgrass (Digi-
taria decumbens Stent), and Coastal bermudagrass (Cynodon
dactylon L. Pers.). [Data were take from Roger et al. (1961).]


Proceedings, Volume 39, 1980
warm season. The legume that has been investigated
most extensively in Florida is white clover (Trifolium
repens L.) in mixture with Pensacola bahiagrass. This
legume is adapted to the Spodosols because of the fre
quent abundance of water and its relatively shallow
root system. White clover has the capacity to fix a
large quantity of N, which is used for its growth in late
winter and early spring. As warm, wet, summer
weather encroaches, white clover plants usually de
teriorate and finally die. With death, the stolons and
roots which have very high N concentrations are de
graded by other soil microorganisms, and N is min
eralized (converted into mineral forms) and used by
the accompanying warm-season grass.
The capacity of the white clover-Pensacola bahia
grass combination on the Spodosols to fix and utilize
atmospheric N is illustrated in Table 5. The legume-
grass combination produced as much forage as the
grass with 224 kg of N/ha/year, and some of this
forage was produced in February and March when
green forage was extremely scarce. Thus, the grazing
season was extended. The N content of the white
clover-grass forages was equal to that contained in
grass alone with a N rate of 448 kg/ha, and some of the
N protein is contained in the February-March clover
production. The quantities of the forage and protein
were equal to those produced by grass with an N ap
plication rate between 224 and 448 kg/ha/year, with
a potential savings of $125 to $250/ha/year. Since
almost no farmer or rancher uses this quantity of fer
tilizer N on pastures, it is readily apparent that pro
duction is not only more economical with the legume-
grass sward but that it is far higher than is normally
achieved from grass alone with fertilizer N.
To grow the legume, it is best not to over-drain the
Spodosols. In some areas of central Florida, irrigation
may be necessary for white clover because winter rains
are less reliable than in north Florida. The soil pH,
Ca, and Mg requirements for legumes are generally
higher than for grasses so more attention must be given
to liming. The requirements for P and K are also more
specific, particularly for seedling development, so care
must be exercised to apply the fertilizer at the proper
time. This should normally be in November. It should
be emphasized, however, that the P and K requirements
of the legume-grass combination under grazing are gen
erally no higher than for the grass alone at a high level
of productivity. Amounts of P and K that must be ap
plied with a grazing system are much less than the
amounts used annually by the plants; utilization ef
ficiencies higher than 100% are a consequence of
nutrient recycling through urine and feces deposited
TABLE 5.Forage production and nitrogen of white clover-
Pensacola BAHIAGRASS AND NITROGEN-FERTILIZED PENSACOLA BAHIA
GRASS ON A SPODOSOL.
N Oven-dry forage Forage N
Forage species applied
Mar. 15
Total
Mar. 15
Total
ks:/ha/year
White clover 4
P. bahiagrass
0
1,990
11,380
71
249
P. bahiagrass
0
0
3,100
0
34
P. bahiagrass
112
0
7,350
0
87
P. bahiagrass
224
0
11,840
0
165
P. bahiagrass
448
0
15,690
0
255
7
by the cattle. Beef (calf) production from white clover
and grass is illustrated by data from the Beef Research
Unit (Table 6). Forage production was approximately
maximum with only 36 kg of P and 67 kg of K/ha/
year. Weaning weights were higher than from grass
alone (Table 4).
The same quantities of P and K were applied to
the grass and to the legume-grass mixture. The grass
received 134 kg of N/ha/year but none was applied to
the legume-grass mixture. Beef production per cow was
substantially higher from the legume-grass than from
grass alone and beef production per ha was about 50 %
higher than from grass with the highest fertilization
rate. The savings by eliminating N fertilizer in this
case would be approximately $59/ha/year.
SUMMARY AND CONCLUSIONS
The production of forages and cattle on Floridas
mineral soils is a complex and relatively expensive
business. Price of inorganic nutrients as lime and fer
tilizer is a major, but by no means the only, produc
tion cost. Forages are produced seasonally and utilized
principally for grazing; therefore, it is frequently dif
ficult to place a value on them. If forage is harvested
for hay, a market value can be fixed and production
costs can be calculated. Thus, the data in Table 2
indicate that 11.2 metric tons of forage can be pro
duced with approximately $194 worth of lime and
fertilizer. Even with some spoilage, the current value
of hay would indicate that this is likely a profitable
operation.
In comparison, we have used fertilizer and beef
production levels from the Beef Research Unit (Roger
et ah, 1961) to compare grass with white clover-grass
(Table 7). Nutrient requirements of the two plant
systems were the same except for fertilizer N which
was applied to the grass; forage production was the
same. Because of better distribution of forage and
higher quality, beef production from the legume-grass
was 40% higher than that from the grass pastures.
Lime and fertilizer costs per kg of beef, at current
prices, are $0.51 for the grass and $0.18 for the legume-
grass pasture.
The perennial grasses are more hardy and more
drought resistant than the annual legumes. Also, dur
ing the growing season, grass production can be con
trolled by adjusting the nutrient supply, particularly
the N level. However, in spite of the excellent response
of grasses to fertilization, the value of the product
when grazed by cows and calves is frequently only
marginally profitable. Legumes require more careful
management and probably are not quite as reliable as
the grass. Even with some shortcomings, legumes must
TABLE 6.Production performance of cows on white clover-
grass PASTURES ON SPODOSOLS, BEEF RESEARCH UNIT.f
Fertilization
Annual
forage
production
Weaning
%
Beef production
N
P
K
Per ha
Per cow
kg/ha/year
kg/ha
kg -
0
36
36
9,810
85
315
171
0
72
72
10,150
82
314
156
fGrasses were Pensacola bahiagrass, Pangla digitgrass, and
Coastal bermudagrass.


8
Soil and Crop Science Society of Florida
TABLE 7.Nutrient costs and beef production from grass and
WHITE CLOVER-GRASS PASTURES ON A SPODOSOL AT THE BEEF RESEARCH
Unit.
Nutrients
Nutrients
Nutrients applied
Rate
Cost
Rate
Cost
kg/ha .fP/ha
Grass
kg/ha $/ha
White
clover-grass
N
134
59
0
0
P
30
30
36
30
K
30
17
36
17
Limef
7.4
7.4
Micronutrients+
2.5
2.5
Total
115.9
56.9
Forage production, kg/ha
9,630
9,810
Beef production, kg/ha
226
316
fData were taken from Koger et al. (1961).
:i:Lirne and micronutrients were prorated using 2.24 metric
tons of dolomitic lime and 28 kg of fritted micronutrients/ha
applied once per 4 to 5-year interval.
be included in the forage program if we are to con
tinue the trend toward intensified beef production.
Some fertilizer N will be needed for production of hay
or silage for winter feeding, but it cannot be the major
stimulus to forage production.
RECOMMENDATIONS
Soil pH should be maintained at approximately
6.0 by application of calcitic and dolomitic lime to
maintain the proper balance of Ca and Mg. Soil tests
through the County Agricultural Extension Agent
should be used as needed. Micronutrients should also
be applied if not previously used. A micronutrient frit
can be used, or alternatively, salts of Mn, Cu, Zn, Fe,
Mo, and B. Directions for their use should be followed
closely to avoid toxicities. For maintenance of a
sustained production system, N, P, and K should be
applied in a 4:0.4:1.7 ratio (4:1:2, N:P205:K20 ratio)
for grasses and a 0:0.4:1.7 ratio (0:1:2, N:P205:K20
ratio) for legume-grass mixtures. Nitrogen can be ap
plied at rates as high as 448 kg/ha/year for grasses for
intensive hay production; normally the rate will be
lower, particularly for grazing. A fertilizer with P and
K in a 0:4:16 ratio at 448 kg/ha/year (0:10:20 at
448 kg) is satisfactory for legume-grass mixtures. This
should be applied in the fall for white clover and in
the spring for summer legumes; a second application
may be made in the spring for white clover. Nitrogen
is not recommended for the legumes if the soil is prop
erly limed and fertilized, and the legumes are inocu
lated. Sulfur should be included annually. A higher
proportion of P may be needed initially, particularly
on soils of west Florida where P fixation may be
relatively severe.
LITERATURE CITED
Barber, S. A., and R. A. Olson. 1968. Fertilizer use on corn,
p. 163-188. In L. B. Nelson (ed.) Changing patterns in fer
tilizer use. Soil Sci. Soc. Am., Madison, Wis.
Blue, W. G. 1971. Nitrogen fertilization in relation to seasonal
Pensacola bahiagrass forage nitrogen and production on
Leon fine sand. Soil and Crop Sci. Soc. Florida Proc. 31:75-77.
Koger, M., W. G. Blue, G. B. Killinger, R. E. L. Greene, H. C.
Harris, J. M. Myers, A. C. Warnick, and N. Gammon, Jr.
1961. Beef production, soil and forage analyses, and economic
returns from eight pasture programs in North Central Florida.
Fla. Agr. Exp. Sta. Tech. Bull. 631.
Koger, M., W. G. Blue, G. B. Killinger, R. E. L. Greene, J. M.
Myers, N. Gammon, Jr., A. C. Warnick, and J. R. Crockett.
1970. Production response and economic returns from five
pasture programs in North Central Florida. Fla. Agr. Exp.
Sta. Tech. Bull. 740.
Koger, M., R. E. L. Greene, G. B. Killinger, W. G. Blue, and
J. M. Myers. 1977. Pasture programs and beef cattle breeding
systems for beef production in North Central Florida. Fla.
Agr. Exp. Sta. Tech. Bull. 789.
Smith, R. L., C. E. Hutton, and W. K. Robertson. 1968. The
effect of nitrogen on the yield of soybeans. Soil and Crop Sci.
Soc. Florida Proc. 28:18-23.
Integrating Native Range and Pasture
E. R. Felton1
This paper outlines the range-management pro
gram currently being followed by ALICO, Inc., a
publicly owned corporation. ALICO stock is traded
over-the-counter. The Company consists of lands for
merly owned as a subsidiary of the Atlantic Coastline
Railroad Company.
Initial development of the land followed guidelines
established by making a comprehensive study of land
types and capabilities. The objective was to develop an
operation that would best utilize this acreage for
sustained agricultural production. There evolved a pro
gram of cattle, citrus, and timber production which are
the main businesses of ALICO, Inc.
In this report, concentration will be on the cattle
operation which includes a range cow/calf operation
in southern Florida combining native and improved
iVice-President, Citrus and Cattle, ALICO, Inc., LaBelle,
Florida 33935.
pastures, and a backgrounding and finishing operation
in southern Georgia. The range cattle operation is
located in Hendry County southeast of LaBelle in
whats known as the Devils Garden area. This area is
typical of the pine, palmetto, and semiprairie country
of central and southern Florida.
Like many ranchers, we went into the cattle busi
ness with native cows crossed with purebred Brahman
bulls. The Brahman cross cows are then bred back to
English bulls (Hereford and Angus). We then follow
a criss-cross breeding system where English bulls are
bred to cows with predominately Brahman character
istics, and Brahman bulls are bred to cows with pre
dominately English characteristics. This produces an
animal with a high degree of hybrid vigor that is well
adapted to south Florida range conditions, and has the
desirable beef type and fleshing ability to respond well
to the backgrounding and finishing operation. The
best quality heifers are kept for herd replacement, and


Proceedings, Volume 39, 1980
the remainder of the heifer and steer calves are shipped
to our Georgia feedlot. These calves are weaned and
shipped at 6 to 8 months of age, heifer calves averaging
160 kg (350 pounds) and steers 204 kg (450 pounds).
Our pasture program is based on a system that com
bines native range and improved pastures in rotational
grazing; a ratio of 0.4 ha (1 acre) improved pasture
and 2 ha (5 acres) native range is used per cow/calf
unit per year. For example, improved pastures are fer
tilized in the spring and early summer, and as growth
starts, the cows with calves are placed on the improved
pastures where they remain until fall when the calves
are weaned. Following weaning, the cows are placed on
native pastures which have been lightly stocked (with
dry cows) or vacated during the summer growing
season. This results in a large amount of roughage ac
cumulated for grazing during the fall, winter, and into
the next spring.
When cows and calves are moved into the improved
pastures in the spring, the calves are branded, marked,
vaccinated, dehorned, and castrated; dry cows are sep
arated and put back on the native range. This has
proven to lie a good economic practice since forage
from fertilized pastures is utilized only by the cow and
calf. Since nutrient requirements of dry cows are con
siderably less than those for cows with calves, we are
able to maintain cows in good condition on the native
range.
The main factor that determines when cows are
rotated from one type pasture to another is weather.
If we have an early spring with good moisture, we
fertilize early and move the cows with calves into the
improved pastures in February or March. During
springs that are subjected to long dry spells, the cows
and calves are not moved until May and early June.
Over a period of years, a cow will average spending 6
months on improved pasture and 6 months on native
range. Flowever, with every period of severe weather,
whether it be flood, drouth or cold, we find ourselves
depending more on the native range. For example, the
severe winters of 1957 and 1962 produced unseasonable
amounts of rain with unusual cold; as a consequence,
there was virtually no production of forage on the im-
9
proved pastures. Flowever, due to reserve roughage in
the native pastures, we were able to maintain our cattle
in satisfactory condition. Even in normal winters the
cool, dry weather causes our Pensacola bahiagrass
(Paspalum notatum Flugge) and Pangla cligitgrass
(Digitaria decumbens Stent.) to become more or less
dormant and they become our poorest pastures. This is
the period when we depend most heavily on the
roughage provided by the native range. Another reason
that we consider the native range to be the backbone of
our cattle business.
Another critical situation that is helped considera
bly by the native-improved pasture system is the strain
of a low cattle market. The economics of our rotational
system are far better than we would realize from a
system of all improved pastures, or one consisting en
tirely of native range.
Our range improvement practices have been very
encouraging in that we have experienced a tremendous
increase in forage production. We chop palmetto-
prairie type range with a Marden chopper during the
winter and early spring, rest during the spring-summer
growing season to permit range plant establishment
and growth, and begin grazing in the fall. This practice
controls undesirable species and increases growth of
better forage plants. It has boosted the yield of range
forage from 1,800 kg/ha (1,600 lbs/acre) to 6,700
kg/ha (6,000 lbs/acre) as measured by the Range Con
servationist of the Soil Conservation Service. The
initial chopping will cost about $52/ha ($21/acre) and
is repeated about every 3 years so that the overall cost
is $17.30/ha ($7/acre/yr). Even with no fertilizer, we
have ranges of well-managed creeping bluestem grass
that are equal in yield to our conservatively fertilized
improved pastures.
Control burning every other year helps maintain
the stand and improves quality of forage on the native
range. These ranges are supplemented with a free
choice mixture of minerals, proteins, and vitamins.
The combination of native range and improved
pasture in the right ratio to provide the proper stock
ing rate has proven to be an economical and efficient
management system.
Properties of Representative Peninsular Florida Soils
Used for Range and Pasture1
Victor W. Carlisle2
ABSTRACT
Physical, chemical, and mineralogical properties of
six soils representative of the six extensively occurring
soil Orders in Peninsular Florida were determined to
provide a better understanding of the behavior of these
soils when used for range and pasture forage produc-
iFlorida Agricultural Experiment Stations Journal Series No.
2264. This research was partially supported by State Legislative
appropriations (administered by the Department of Agriculture
and Consumer Services) and supplemental funds contributed by
participating counties in support of the Florida Cooperative Soil
Survey.
2Professor of Soil Science, Soil Science Department, University
of Florida, Gainesville, FL 32611.
lion. Particle size distribution of all mineral soils was
dominated by quartz sand. Water retention values were
greater in horizons containing enhanced amounts of
organic C and in argillic horizons. Extractable Ca and
Mg were low in all mineral soils and high in the or
ganic soil. Extractable Na and K were low in all soils.
Cation exchange capacity was generally highest in sur
face horizons which usually contained largest amounts
of organic C but CEC also increased in the argillic and
spodic horizons. Surface soil pH was acid in all soils.
Varying amounts of montmorillonite, 14 intergrades,
kaolinite, gibbsite, and quartz were identified from
X-ray diffraction patterns.
Additional Index Words: Soil characterization, Al-
fisol, Entisol, Histosol, Inceptisol, Spodosol, Ultisol.


10
Soil and Crop Science Society of Florida
Most improved pasture in Florida is grazed in com
bination with large areas of native range. Ranches are
large, the most common size being about 1,600 ha
(Carter, 1978). Fourteen hundred of the larger ranches
in Peninsular Florida are operating on approximately
4,200,000 ha. Some animals are kept on improved pas
ture continuously, but most of them have access to
native range during at least part of the year.
Roger et al. (1961) in a comprehensive study of
pasture programs reported highest net returns from
grass-clover pastures that were not irrigated. Similar
results were reported by Peacock et al. (1975) compar
ing native range, native range plus improved grasses,
and improved grass-clover pastures. Regardless of the
production systems used, soil characteristics and man
agement practices largely determine the relative eco
nomic merit of various forage species.
The objective of this research was to compile soil
characterization data that would provide a better un
derstanding of the behavior of representative Peninsu
lar Florida soils when used for range and pasture
forage production.
MATERIALS AND METHODS
Six soils representing six commonly occurring soil
Orders were sampled from freshly exposed pits at dif
ferent geographical locations in Peninsular Florida
(Fig. 1). All horizons were described and sampled for
characterization by the Florida Soil Characterization
Laboratory at Gainesville; however, only laboratory
results for the major horizons of each pedon are pre
sented in this study. In addition to bulk samples, un
disturbed 5.4 x 3.0 cm cores were collected from most
horizons for bulk density, water retaining, and water
transmitting properties.
Samples were air-dried, passed through a 2-mm
aluminum sieve, and thoroughly mixed before pro
ceeding with particle size distribution, chemical, and
mineralogical analyses. Particle size distribution was
determined by the hydrometer procedure of Bouyoucos
(1962) modified by determining actual weights of sand
fractions. Soil cores were placed in Tempe pressure
cells, saturated, and then extracted at sequential pres
sures to determine water retained at 1/10 and 1/3 bars.
Before drying, the cores were resaturated for determi
nation of saturated hydraulic conductivity. After oven
drying the samples were ground to pass a 2-mm sieve
and the 15-bar water retention was determined.
Extractable bases were replaced by leaching 25 g
of soil with 250 ml of LOA NH,OAc buffered at pH
7.0. Calcium and Mg were determined by atomic ab
sorption; K and Na by flame emission. Extractable
acidity was determined by the BaCL-triethanolamine
(pH 8.2) method. Cation exchange capacity (CEC) was
calculated from the sum of extractable cations and
acidity. Organic C was determined by acid dichromate
digestion and soil reaction (pH) by glass electrode in
1:1 soil-liquid ratios of water and LOA KC1.
Clay was separated from sand and silt by wet siev
ing, centrifugation, and decantation. X-ray diffraction
patterns were obtained with a General Electric XRD-7
instrument using graphite-filtered CuKa radiation.
Samples were prepared for analysis by orienting ap
proximately 225 mg of clay on unglazed ceramic tile
(Rich, 1969). X-ray diffractograms were obtained from
Mg-saturated glycerol-solvated samples with no heat
treatment, K-saturated samples with no heat treatment,
and K-saturated samples after heating to 550 C for 4
hours. Relative amounts of clay minerals were esti
mated from the X-ray diffractograms.
RESULTS AND DISCUSSION
Soils selected for this study are commonly used for
range and pasture in Peninsular Florida. They belong
to the excessively, well, poorly, and very poorly soil
drainage classes (Table 1). As indicated by the family
classification, all of these soils occur in the hyper
thermic temperature zone and none contain appreci
able weatherable minerals. The Candler soil is un
coated (less than 5% silt plus clay in the control
section) and the Pahokee is an organic soil with high
base saturation (euic). Argillic horizons are present
only in the Arredondo and Felda soils.
The sandy nature of the mineral soils investigated
is indicated in Table 2. With exception of the organic
soil (Pahokee), sand was by far the major fraction in
all pedons. Surface horizons of all soils, except Pahokee,
contained more than 89% sand. Candler, Myakka, and
Placid soils contained in excess of 92% sands in sub
soils to depths of 2 m. Silt contents of these soils ranged
from 0.5 to 3.9%. Argillic horizons in the Arredondo
and Felda subsoils contained a preponderance of sands,
low silt content similar to the other mineral soils, and
an enhancement of clay ranging from 8.5 to 36.7%.
Distribution of sand fractions in the upper horizons of
the mineral soils indicated considerable homogeneity
of parent materials in these soils. Particle size distribu
tion was not attempted on the Pahokee soil.
Hydraulic conductivities (Table 2) of the sandy
horizons in these soils were quite high, frequently in
excess of 15 cm/hr. Predictably, the highest hydraulic
conductivity values were recorded for the excessively
drained Candler soil and the lowest values for argillic
horizons occurring at considerable depth in the Ar
redondo and Felda soils. Although hydraulic conduc
tivity was lower in the spodic horizon than other hori
zons determined for the Myakka soil, it was consider
ably higher than values commonly recorded for
Fig. 1 .Location of sample sites.


Proceedings, Volume 39, 1980
11
TABLE 1.Classification and natural drainage of selected soils.
Classification Natural
Soil Order Subgroup Family Drainage
Arredondo
Ultisol
Grossarenic Paleudult
Loamy, siliceous, hyperthermic
Well
Candler
Entisol
Typic Quartzipsamment
Uncoated, hyperthermic
Excessively
Felda
Alfisol
Arenic Ochraqualf
Loamy, siliceous, hyperthermic
Poorly
Myakka
Spodosol
Aerie Flaplaquod
Sandy, siliceous, hyperthermic
Poorly
Pahokee
Histosol
Lithic Medisaprist
Euic, hyperthermic
Very Poorly
Placid
Inceptisol
Typic Humaquept
Sandy, siliceous, hyperthermic
Very Poorly
TABLE 2.Physical properties of selected soil horizons.
Bulk
Particle size distribution
Hydr.
cond.
density
field
1/10
Water content
1/3
15
Soil
Depth
Horizon
Sand
Silt
Clay
(sat.)
moist
bar
bar
bar
cm
% of <2
mm
cm/hr
g/cc
% (wt) ......
Arredondo
0-20
Ap
90.7
5.6
3.7
14.9
1.49
10.0
6.5
2.5
104-137
A23
97.4
0.8
1.8
26.1
1.54
3.7
1.8
0.7
157-175
B21t
86.7
0.0
13.3
1.0
1.67
16.5
12.7
6.4
175-203
B22t
62.4
0.9
36.7
0.1
1.58
24.5
22.1
12.2
Candler
0-8
A1
95.9
2.7
1.4
_
_
43-89
A23
96.9
1.2
1.9
77.6
1.50
2.7
1.7
0.7
89-203
A24
97.4
0.8
1.8
78.2
1.45
3.0
2.1
0.8
Felda
0-10
Ap
98.3
0.8
0.9
17.1
1.52
9.3
6.7
2.6
53-79
A23
96.8
2.4
0.8
13.2
1.60
6.3
2.5
0.9
79-112
B2H
84.4
4.6
11.0
0.1
1.68
19.6
17.3
7.7
147-203
B23tg
87.4
4.1
8.5

-
-
-
-
Myakka
0-8
A1
98.1
1.2
0.7
57.8
1.31
9.4
6.9
4.1
15-66
A22
99.0
0.5
0.5
30.9
1.44
4.8
3.1
1.9
66-76
B21h
92.2
4.7
3.1
26.5
1.44
20.2
13.3
2.7
160-203
B3&Bh
98.1
0.9
1.0

-
-
-
-
Pahokee
0-25
Oap


_
13.8
0.38
255.0
161.0
25-71
Oa2



40.5
0.13

440.0
277.4
71-107
Oa3


35.8
0.13
-
390.0
252.0
Placid
0-36
All
89.5
6.6
3.9
7.0
1.28
30.0
22.6
5.9
61-91
Cl
98.1
1.4
0.5
15.8
1.49
11.6
6.1
1.7
127-203
C3
98.6
0.9
0.5
23.6
1.56
4.3
2.8
1.4
Myakka soils in many other Florida locations (Cal
houn et ah, 1974; Carlisle et ah, 1978). In somewhat
poorly and poorly drained soils, horizons with low
hydraulic conductivity may perch a temporary water-
table for several days or weeks. If this perched water-
table is within reach of active plant roots, plants may
seasonally utilize far more water from the soil than
would be predicted from soil water retention data
alone. Differences in bulk density values were not
great in the mineral soils with slightly lower values in
surface horizons due to less compaction and higher
amounts of organic matter. Bulk density values for all
sapric horizons in the Pahokee soil were extremely low
due to the high content of organic matter in this
Histosol.
Water contents at 1/10, 1/3, and 15 bars (Table 2)
show lowest water retention in the excessively drained
Candler soil and highest amounts in the very poorly
drained organic soil (Pahokee). Retention of water is
somewhat greater in the surface horizons of the mineral
soils due to enhanced contents of organic matter. Ar
redondo and Felda soils have subsurface horizons with
greater amounts of clay. Retention of water in these
horizons is influenced by the clay content and retention
of larger amounts of water in the spodic horizon of the
Myakka soil is influenced by slightly higher clay con
tent and much higher organic matter content.
Generally, low values for extractable bases in the
Arredondo, Candler, Felda, Myakka, and Placid soils
(Table 3) are indicative of low inherent soil fertility.
Calcium and Mg were the predominant cations with
largest amounts occurring in the surface soils and
argillic horizons. Sodium was uniformly low and the
trace amounts of K further support the absence of
appreciable quantities of weatherable minerals in
these soils. Cation exchange capacity in these soils is
usually less than 10 meq/100 g. Lower CEC values oc
curred in the sandier horizons containing negligible
amounts of organic C. Small amounts of liming ma
terials applied to surface soils with low CEC will sig
nificantly alter soil reaction in the upper horizons. As
expected, extractable Ca and Mg were very high in the
Pahokee soil resulting in CEC values more than 10
times those recorded for the mineral soils. Also ex
pectedly, organic C contents were highest in the
Pahokee soil. Mineral soils contained highest organic
C contents in surface horizons, decreasing rapidly with
depth in all but the Myakka soil in which organic C
increased abruptly in the spodic horizon. Organic C
contents may be increased: by good management prac-


12
Soil and Crop Science Society of Florida
TABLE 3.Chemical properties of selected soil horizons.
Soil
Depth
Horizon
Ca
Extractable bases
Mg Na K
Sum
Extract.
acidity
CEC
Base
sat.
Organic
carbon
pH
H,0 KC1
(1:1) 1.0N
(1:1)
cm
meq/100g
%
%
Arredondo
0-20
Ap
2.8
1.0
tr
tr
3.8
5.8
9.6
40
1.43
5.4
4.8
104-137
A23
0.1
tr
0.0
tr
0.1
0.2
0.3
33
0.20
6.1
5.5
157-175
B21t
0.9
0.2
tr
tr
1.1
2.1
3.2
34
0.07
5.8
4.8
175-203
B22t
0.3
1.1
tr
tr
1.4
8.9
10.3
14
0.14
5.0
3.8
Candler
0-8
A1
1.3
0.2
tr
0.1
1.6
1.6
3.2
48
0.46
5.4
4.8
43-89
A23
0.1
tr
tr
0.1
0.2
1.0
1.2
16
0.02
5.7
4.6
89-203
A24
0.1
tr
tr
0.1
0.2
1.2
1.4
12
0.02
5.5
4.6
Felda
0-10
Ap
0.3
0.1
tr
tr
0.4
4.4
4.8
9
1.56
4.8
3.8
53-79
A23
0.3
0.1
tr
tr
0.4
0.2
0.6
61
0.04
6.1
5.5
79-112
B211
3.1
3.1
0.3
tr
6.5
2.9
9.4
69
0.11
6.9
6.2
147-203
B23tg
5.8
1.7
0.2
tr
7.7
1.7
9.4
. 82
0.07
6.5
5.9
Myakka
0-8
A1
0.3
0.2
0.1
tr
0.6
4.6
5.2
11
1.39
4.3
3.3
15-66
A22
tr
tr
tr
tr

0.8
0.8
7
0.12
5.6
4.1
66-76
B21h
0.1
0.1
0.1
tr
0.3
13.9
14.2
3
2.27
4.4
3.5
160-203
B3&Bh
tr
tr
tr
tr

6.6
6.6
1
0.71
5.1
4.5
Pahokee
0-25
Oap
107.8
24.8
2.6
0.6
135.8
0.8
136.6
99
37.60
6.1
5.6
25-71
Oa2
72.4
17.8
2.7
0.9
93.8
7.7
101.5
92
38.60
6.5
6.0
71-107
Oa3
54.6
17.3
2.9
1.0
75.8
8.7
84.5
90
37.60
6.2
5.8
Placid
0-36
All
0.5
0.2
0.1
tr
0.8
9.2
10.0
8
1.92
4.4
3.3
61-91
Cl
tr
tr
tr
tr




0.12
5.9
4.4
127-203
C3
tr
tr
tr
tr




0.06
6.3
4.8
tices. Blue (1979) reported changes from approxi
mately 1.1 to 2.5% organic C in the surface soil of a
Myakka fine sand during 25 years of continuous grass-
clover pasture.
Soil reaction (FLO) ranged from pH 4.3 to pH 6.9,
seldom varying more than 1.5 pH units between hori
zons of the same profile. The pH values in l.(W KC1
were between 0.4 and 1.5 pH units lower than the
water measurements.
Sand fraction (>50pm) mineralogy is siliceous in
the Arredondo, Candler, Felda, Myakka, and Placid
soils with quartz dominant in all pedons. Very small
amounts of ilmenite and other heavy minerals (not
reported) occurred in most horizons with the greatest
concentration in the very fine sand fraction. Mineral
ogy of the crystalline components of the clay fraction
(Table 4) indicated that this fraction was dominated
by a variety of clay minerals in the soil Orders occur
ring extensively throughout Peninsular Florida.
Kaolinite was the dominant mineral (Table 4) in
the Arredondo soil; 14 intergrades in the Candler;
montmorillonite in the Felda; and quartz in the
Myakka and Placid soils. Similar results were pub
lished for Aerie Haplaquods (Zelazny and Carlisle,
1971), Typic Quartzipsamments (Carlisle and Zelazny,
1975), and Grossarenic Paleuclults (Carlisle, 1976) in
TABLE 4.Clay mineralogy of selected soil horizons.
Soil
Depth
Horizon
Mont
morillonite
14
Intergrade
Kaolinite
Gibbsite
Quartz
Amorphous
cm
%, X-ray peak intensity
Arredondo
0-20
Ap
33
56
11
104-137
A23

41
41

18
157-175
B21t
6
29
60

5
175-203
B22t
17
18
54
-
11
Candler
0-8
A1
34
34
6
26
43-89
A23

36
22
15
27
89-203
A24
-
32
24
14
30
Felda
0-10
Ap
38
62
79-112
B21t
97


_
3
147-203
B23tg
97

1

2
Myakka
0-8
A1



100
66-76
B21h
31



69
160-203
B3&Bh
-
-
-
-

100
Placid
0-36
All
100
61-90
Cl
7
27
28

38
127 203
C3

20
16

64


Proceedings, Volume 39, 1980
other Peninsular Florida locations. Primarily due to
the relatively low amounts of clay occurring in the
surface horizons, clay mineralogy of Florida soils com
monly influences their suitability for range and pasture
less frequently than the total clay content.
According to Henderson (1952), soil characteristics
that should be considered for range and pasture pro
grams in Florida are: (a) texture, (b) organic matter
content, (c) reaction of surface horizon, (d) depth to
clay, (e) natural drainage or depth to watertable, and
(f) slope. These important properties influence soil
moisture and plant nutrient relationships; therefore,
the nature of the soil largely determines which species
should be grown and the management practices which
must be used for maximum forage production.
Data presented for Peninsular Florida soils show
close agreement with Soil Conservation Service native
rangeland plant production ratings: Pahokee > Placid
> Felcla > Myakka > Arredondo > Candler (personal
communication with Mr. C. W. Carter, Range Con
servationist, U.S. Department of Agriculture, Soil Con
servation Service, Gainesville, FL 32601). Similar re
sults may be expected for improved pastures; however,
productivity is usually modified by such practices as
water control, liming, and fertilization.
LITERATURE CITED
Blue, W. G. 1979. Forage production and N contents, and soil
changes during 25 years of continuous white clover-Pensacola
bahiagrass growth on a Florida Spodosol. Agron. J. 71:795-798.
13
Bouyoucos, G. J. 1962. Hydrometer method improved for making
particle analyses of soils. Agron. J. 54:464-465.
Calhoun, F. G., V. W. Carlisle, R. E. Caldwell, L. W. Zelazny,
L. C. Hammond, and H. L. Breland. 1974. Characterization
data for selected Florida soils. Soil Science Department Re
search Report No. 741.
Carlisle, V. W. 1976. Mineralogy of selected Florida Grossarenic
Paleudults and Ultic Hapludalfs. Soil and Crop Sci. Soc. Flor
ida Proc. 36:126-129.
Carlisle, V. W R. E. Caldwell, F. Sodek, III, L. C. Hammond,
F. G. Calhoun, M. A. Granger, and H. L. Breland. 1978.
Characterization data for selected Florida soils. Soil Science
Department Research Report No. 78-1.
Carlisle, V. W., and L. W. Zelazny. 1975. Pedon mineralogy of
representative Florida Typic Quartzipsamments. Soil and
Crop Sci. Soc. Florida Proc. 34:4347.
Carter, C. W. 1978. Ranching in the sunshine. Rangemans J. 5:
82-83.
Henderson, J. R. 1952. Florida pastures from the extension view
point. Soil and Crop Sci. Soc. Florida Proc. 12:105.
Roger, M W. G. Blue, G. B. Killinger, R. E. L. Greene, H. C.
Harris, J. M. Myers, A. C. Warnick, and N. Gammon, Jr. 1961.
Beef production, soil and forage analyses, and economic re
turns from eight pasture programs in north central Florida.
Florida Ag. Exp. Sta. Bull. 631.
Peacock, F. M R. E. L. Greene, E. M. Hodges, W. G. Kirk, and
M. Roger. 1975. Forage systems as related to the economics
of beef production in south central Florida. Soil and Crop
Sci. Soc. Florida Proc. 34:148-151.
Rich, C. I. 1969. Suction apparatus for mounting clay specimens
on ceramic tile for X-ray diffraction. Soil Sci. Soc. Amer. Proc.
33:815-816.
Zelazny, L. W and V. W. Carlisle. 1971. Mineralogy of Florida
Aerie Haplaquods. Soil and Crop Sci. Soc. Florida Proc. 31:
161-165.


14
Soil and Crop Science Society of Florida
SOILS SECTION
Fruit Yield of Florida Belle Strawberries as Affected by
Rates of a Resin Coated Fertilizer1
E. E. Albregts and C. M. Howard2
ABSTRACT
A resin-coated slow-release fertilizer called Osmocote
is used extensively in strawberry (Fragaria x ananassa,
Duch.) fruit production to reduce fertilizer leaching,
but only limited data are available as to the effect of
Osmocote rate on fruit yield with sandy soils. Rates of
700, 1050, and 1400 kg/ha of a 16-2.2-13.3 Osmocote
were evaluated during two seasons with overhead
sprinkler irrigation and during one season with drip
irrigation. Several fertilizer placements were used. Soil
tests taken prior to fertilizer application indicated high
levels of P and K in the soil. The soil organic matter
content was rated as low. Total yield, fruit weight,
plant size, and foliage color were not different because
of Osmocote rates or placements with either overhead
sprinkler or drip irrigation. Soil soluble salts were
above yield limiting levels and tended to increase with
increasing rates of Osmocote.
Additional Index Words: Slow-release fertilizer,
Scranton fine sand, Fertilizer placement.
Most strawberry (Fragaria x ananassa, Duch.) grow
ers include a slow-release N fertilizer as part of their
total N application. However, many growers use a fer
tilizer derived solely from a resin-coated slow-release
source named Osmocote.3 These growers wish to
eliminate the leaching that can occur with the inor
ganic fertilizer sources and overhead sprinkler irriga
tion (3, 4, 6, 9). Osmocote fertilizer will maintain a
higher soluble salts, NO,, and NH, concentration in
the root zone than will inorganic fertilizer (4). The
additional cost of Osmocote is justified by the as
surance that sufficient N and K will be available when
the plants need them (4). However, little research has
been done in Florida on the effect of Osmocote rates
on strawberry fruit yield. Osmocote is a resin-coated
fertilizer whose release rate is affected mostly by tem
perature (8). Since it is relatively expensive, growers
using Osmocote or any other fertilizer should apply no
more than is needed to grow the crop so as to control
production costs, energy inputs, and pollution. The
purpose of this study was to evaluate the effect of
Osmocote rates on fruit yields and soil soluble salts
with overhead and drip irrigation in a well drained
sandy soil.
MATERIALS AND METHODS
Experiments were conducted for three seasons
(1977 to 1979) on a well drained Scranton adjunct fine
sand (a siliceous, acid, thermic Typic Psammaquent)
iFlorida Agricultural Experiment Stations Journal Series No.
1968.
"Professors (Soil Chemistry and Plant Pathology, respec
tively), Agricultural Research Center, Dover, FL 33527.
3The use of trade names in this publication does not con
stitute an endorsement of the product.
at the Agricultural Research Center, Dover. Three
rates (700, 1050, and 1400 kg/ha) of Osmocote 16-2.2-
13.3, a formulation designed to become available in
the soil solution over a 7 to 8 month period, were ap
plied each season to black polyethylene mulched beds
fumigated with a mixture of methyl bromide and
chloropicrin. The fertilizer was banded in the bed
center about 3 cm below the soil surface the first
season. During the second season, fertilizer was ap
plied either (a) as in the previous season, (b) banded
10 cm deep under each plant row, or (c) banded 10 cm
deep and 5 cm inside plant rows. During the third
season, the fertilizer was banded 10 cm deep under
each plant row. A standard fertilizer practice (inor
ganic fertilizer) was not used in this study because
Osmocote, applied at the highest rate used in this
study, had been evaluated previously against the
standard practice and was shown to be a superior
product with respect to the retention of nutrients in
the root zone (3, 4). The area used for the experiment
during the third season was different from that used
the previous 2 years. During the first two seasons over
head sprinkler irrigation was used, and during the
third season drip irrigation was used. Sufficient irriga
tion was applied so as to keep beds moist. Florida
Belle strawberry plants were set each year during
October in double-row beds and irrigated with over
head sprinkler irrigation for establishment. Marketable
fruit were harvested, counted, and weighed twice
weekly from January through April. Soil samples were
taken at the end of the harvest season during the last
two seasons and at mid-harvest as well during the last
season. Five cores were taken across the plant bed in
two places in each plot to a depth of 15 cm with at
least one of each of the five cores coming from the fer
tilizer band. Care was taken during soil sampling and
extraction of the saturated soil solution so as to not
crush the Osmocote pellet. All cores from each plot
were then composited. Samples were analyzed for total
soluble salts and reported in mhos/cm x 103 electrical
conductivity at soil saturation. Soil samples were also
taken in the fall of 1976 and 1978 before fertilizer
application and extracted with the double acid ex
tracting solution (7). The 1976 soil test results indi
cated that the soil P and K were high (151 and 192
kg/ha P and K, respectively). The soil had a pH of
6.5, and the soil organic matter content was rated as
low. The 1978 soil test results also rated soil P and K
as high (151 and 142 kg/ha P and K, respectively).
The soil had a pH of 7.2, and the soil organic matter
content was rated as low. The saturated extracts from
these same soil samples had an electrical conductivity
of 0.20 and 0.10 mhos/cm at 25C for 1976 and 1978,
respectively. Plants were rated for color of foliage and
size at least twice per season. Plant size at each sam
pling date was rated on a scale of 1 to 10 with 10 being
the largest plant. Foliage color was rated on a scale of
1 to 4 with 1 being yellow and 4 being dark green.


15
Proceedings, Volume 39, 1980
RESULTS AND DISCUSSION
The foliage color was rated medium to dark green
during all seasons, and fertilizer treatments did not
affect foliage color except during March of the first
season (Table 1). Plant growth did not vary because
of treatment except during the first season, but growth
the first season was not improved with Osmocote rates
greater than 700 kg/ha. Reduction of the early plant
growth can be indicative of low soil fertility. January
fruit yields did not vary because of Osmocote rate or
placement except during the first season. April fruit
yields were not affected by Osmocote rate or place
ment during any season. An insufficient fertilizer rate
would more likely affect fruit yields late in the season
(April) with a long season crop such as strawberries.
Although total markeable fruit yields were less during
the second season, total marketable yields were not
different because of Osmocote rate or placement for
any season. Total marketable fruit yields were con
siderably greater than the average Florida yields (16.8
metric tons/ha) for the 1976-78 period (5). Average
marketable fruit weight was not different because of
treatment for any season. Fruit size may be reduced if
fertility is low (4).
The total soil soluble salts generally increased with
increasing rates of Osmocote, and the differences were
significant on two of the three sampling dates (Table
2). The total soil soluble salts in all treatments were
sufficient to produce high fruit yields (1, 2, 4).
The initial fertility of the soil used in these studies
with respect to K and P was high. The amounts of N,
K, and P applied to the soil by the lowest rate of
TABLE 2-Total soil soluble salt in top 15 cm of bed at vari
ous DATES.
Fertilizer
rate
April 1978
placementf
February
1979
April
1979
I
M
U
kg/ha
EC (mhos/cm x 103)f
700
1.91
2.15
2.10
4.37
1.88
1050
3.23
3.85
2.32
4.42
2.17
1400
3.33
5.63
2.10
10.67
2.62
§L##
L**
ns
L**
ns
fl = fertilizer banded 7 cm deep and 5 cm inside plant rows,
M = fertilizer banded in bed center 3 cm below surface, U = fer
tilizer banded under plant row.
^Conductivity of saturated soil extract.
§ Significance: L = linear, ** = 1% level.
Osmocote were If2, 93, and 15 kg/ha, respectively.
With respect to the fruit yields obtained in these
studies, the total uptake of N, K, and P would have
been less than 80, 80, and 12 kg/ha, respectively (2).
Therefore, with the soil supplying some of the N, K,
and P and with a slow-release fertilizer applied at rates
greater than plant uptake, the lower rates of Osmocote
used in these studies should have been sufficient to
produce the optimum yields obtained. The rate of
Osmocote to use on a particular soil will be dependent
on soil type, initial soil fertility, cultural system em
ployed, and cultivar grown. The application of rela
tively low rates of slow-release fertilizers to straw
berries makes their use more economically feasible.
TABLE LEffect of osmocote rate and placement on plant size, foliage color, marketable
FRUIT YIELD, AND AVERAGE FRUIT WEIGHT FOR THREE SEASONS.
Fertilizer
Yield (Mt/ha)
Seasonal avg.
fruit wt. (g)
Plant sizef
Foliage colonj:
January
April
Seasonal
December
March
December
March
Rate (kg/ha)
1976-77
700
2.3
2.5
27.9
16.7
9.2
9.8
3.8
3.0
1050
1.8
2.3
26.7
15.9
8.6
9.6
4.0
3.4
1400
4.2
4.0
27.8
16.7
9.2
9.8
4.0
3.2
§L*
ns
ns
ns
Q*
Q*
ns
Q*
Placement!! and
rate (kg/ha)
1977-78
I- 700
7.0
4.9
21.5
16.3
9.4
9.8
4.0
3.8
1050
7.2
6.3
23.7
14.8
9.6
9.4
4.0
3.2
1400
6.3
3.3
18.2
16.2
8.8
9.2
4.0
3.6
M- 700
5.8
5.9
22.7
15.6
8.6
9.4
3.8
3.4
1050
6.1
4.1
20.1
15.6
8.6
9.0
3.8
3.4
1400
5.9
5.1
20.2
16.2
8.6
9.0
3.8
3.2
U- 700
7.0
4.3
20.0
16.3
9.0
9.6
4.0
3.4
1050
6.5
4.4
20.0
15.3
8.8
9.8
4.0
3.2
1400
7.4
4.1
19.7
16.3
9.4
9.4
4.0
3.4
ns
ns
ns
ns
ns
ns
ns
ns
Rate (kg/ha)
1978-79#
700
4.2
17.6
28.3
14.6
9.3
9.7
4.0
4.0
1050
4.3
16.5
27.8
14.1
9.4
9.8
4.0
4.0
1400
4.0
15.8
26.7
14.7
9.2
9.6
4.0
4.0
ns
ns
ns
ns
ns
ns
ns
ns
fRelative plant size for date: Plant size rated on scale of 1 to 10 with largest plants rated as 10.
JColor rated on scale of 1 to 4 with 1 = yellow, 2 = light green, 3 = medium green, and 4 = dark green.
§Signilicance: L = linear, Q = quadratic. 5% level.
If I = fertilizer banded 7 cm deep and 5 cm inside plant rows, M = fertilizer banded in bed center 3 cm below surface, U = fertilizer
banded under plant row.
#Drip irrigation used in 1978-79; overhead sprinkler irrigation used in other years.


16
Soil and Crop Science Society of Florida
Lower rates of slow-release fertilizers are possible be-
case they maintain a higher soil nutrient level than
inorganic sources when applied at the same rate (4).
REFERENCES
1. Albregts, E. E., and C. M. Howard. 1973. Influence o£ fer
tilizer placement and rates on strawberry production and soil
fertility. Soil and Crop Sci. Soc. Fla. Proc. 32:89-92.
2. and 1977. Strawberry fertilization.
Dover ARC Research Report SV-1977-2.
3. and 1978. Influence of fertilizer sources
and drip irrigation on strawberries. Soil and Crop Sci. Soc.
Fla. Proc. 37:159-162.
4. and 1979. Effect of bed height and N
fertilizer sources on fruiting strawberries. Soil and Crop Sci.
Soc. Fla. Proc. 38:76-78.
5. Dozier, G. L. 1979. Marketing Louisiana Strawberries, 1979
crops. Louisiana State Market News Service.
6. Everett, P. H. 1978. Controlled release fertilizer: Effect of
rates and placement on plant stand, early growth, and fruit
yield of peppers. Fla. State Hort. Soc. Proc. 90:390-393.
7. Nelson, W. L., A. Mehlich, and E. Winters. 1953. The de
velopment, evaluation, and use of soil tests for phosphorus
availability. Agron. J. 4:153-188.
8. Patel, A. S., and G. C. Sharma. 1977. Nitrogen release char
acteristics of controlled-release fertilizer during a four month
soil incubation. J. Amer. Soc. Hart. Sci. 102:363-367.
9. Rhoads, F. M. 1977. Water and nutrient movement under a
surface moisture barrier in a sandy soil. Soil and Crop. Sci.
Soc. Fla. Proc. 36:68-71.
Copper Nutrition of Cucumber (Cucumis sativus L.)
as Influenced by Fertilizer Placement, Phosphorus Rate,
and Phosphorus Source1
A. A. Navarro and S. J. Locascio2
ABSTRACT
The effects of Cu rate, P rate and source, and fer
tilizer placement on cucumbers (Cucumis sativus L.)
were studied in field experiments on St. Johns fine sand
(sandy, siliceous, hyperthermic Typic Haplaquod). An
increase in Cu from 0 to 2.24 kg/ha increased total
yields from 11.2 to 21.4 ton/ha. A further increase in
Cu to 8.96 kg/ha increased yield to 24.7 ton/ha.
Cucumbers also responded significantly to P applica
tions. At P rates of 0, 28, 56, and 112 kg/ha, yields were
15.8, 21.2, 20.3, and 19.9 ton/ha, respectively. An inter
action between P and Cu rate on early yield was sig
nificant. Application of high Cu rates with low P rates
or high P rates with low Cu rates reduced yields. Yields
were highest with Cu applied at 8.96 and P at 56 kg/ha.
Fertilizer placement interacted with Cu rate on early
and total yields. An increase in Cu rate from 0 to 8.96
kg/ha increased yields 154% with the broadcast place
ment and 82% with the band placement. Total yields
were significantly greater with ordinary superphos
phate as the P source than with either diammonium
phosphate or concentrated superphosphate which were
comparable. Increased rates of P resulted in increased
P concentrations in plant tissues, but significantly re
duced tissue Cu 30 days after planting and at the har
vest stage. Increased rates of Cu increased tissue Cu at
both growth stages, but decreased P concentration at
the harvest stage.
Additional Index Words: Cu rate, Band placement,
Broadcast placement.
In Florida, early studies on Cu requirements of
vegetables were limited to organic soils (1). On mineral
soils, more recent studies have shown substantial re
sponses to Cu application for watermelons (7, 9).
J Florida Agricultural Experiment Stations Journal Series No.
2147.
^Formerly Graduate Assistant and Horticulturist, Vegetable
Crops Department, respectively, University of Florida, Gaines
ville, FL 32611.
Watermelon response to organic sources of N were
shown to be due primarily to Cu impurities in the
fertilizer (7). Watermelon requirement for Cu when
grown on a number of mineral soils was approximately
4.48 kg/ha. Phosphorus rate and source were found to
influence Cu uptake (5, 9). Increased rates of applied
P depressed Cu uptake by watermelons and reduced
yields unless Cu rates were also increased. Fertilizer
placement was also found to affect watermelon yield
(6, 10) and Cu uptake (11); its effect was most pro
nounced at high Cu levels. The purpose of this study
was to evaluate the effects of P rate, P source, and fer
tilizer placement on Cu requirements of cucumbers
(Cucumis sativus L.).
MATERIALS AND METHODS
Field Experiments: Two similar experiments were
conducted in 1971 and 1972 on two adjacent newly
cleared areas of St. Johns fine sand located near Gaines
ville. The soil pFI was 3.9 with 5.5% organic matter
content and 1 ppm Cu. Treatments were factorial com
binations of three P sources, diammonium phosphate
(DAP), ordinary superphosphate (OSP), and concen
trated superphosphate (CSP); four P rates, 0, 28, 56,
and 112 kg/ha; four Cu rates, 0, 2.24, 4.48, and 8.96
kg/ha; and two fertilizer placements, band and broad
cast.
Fertilizer treatments were formulated to include N
at 134 kg/ha (one-fourth in the nitrate form, and
three-fourths in the ammonium form), and 134 kg/ha
of K equally from KC1 and K2S04. Treatments were
arranged in a randomized block design with three
replications.
In 1971, the field was limed 1 week before planting
and in 1972 lime was applied 1 month before planting.
In both seasons, CaC03 was applied at 9,000 kg/ha
which raised the soil pH to 5.5. Fertilizer was applied
before planting on beds 1.2 m apart. With the band
placement, the fertilizer was applied in a single band
located 6.4 cm deep and 6.4 cm to the side of bed
center. For the broadcast placement, fertilizer was ap
plied in a 1-m strip on the bed surface and incorpo-


17
Proceedings, Volume 39, 1980
rated to a depth of 15 to 20 cm. Poinsett cucumber
seeds were planted in a single row in the bed center.
Seedlings were thinned to a final spacing of 61 cm. At
the last thinning (30 days after seeding), plants were
sideclressed with 34 kg/ha N as NH.,N03.
First fruits were harvested 55 days after planting
and harvests continued at 3 to 4-clay intervals for eight
harvests in 1971 and five in 1972. Whole plant samples
were collected for tissue analyses 30 days after planting
and recently mature leaves were sampled at harvest.
Plant tissues were oven-dried (70C) and ground with
a Wiley mill. Two-gram samples of the tissues were
dry-ashed at 500C. The ash was disolved in 50 ml of
IN HCL. A 25-rnl aliquot was evaporated to dryness on
a hot plate and volume brought back to 10 ml with IN
HC1. Copper and Fe were determined by atomic ab
sorption spectrometry and P was determined color-
imetrically by the phosphomolybdate method (8).
RESULTS
Effects of Cu rate. The main effects of Cu rate on
total yield of cucumbers for the two seasons are shown
in Table 1. Response to Cu varied during the two
seasons. With an increase in Cu rate, yields were in
creased over four times in 1971 and almost doubled
during 1972. Yields with the 0, 2.24, 4.48, and 8.96 kg
Cu/ha rates were 3.6, 10.6, 11.4, and 15.2 ton/ha in
1971 and 18.9, 32.1, 31.4, and 34.2 ton/ha in 1972, re
spectively. Application of Cu resulted in an increase
in tissue Cu concentration 30 days after seeding and at
harvest (Table 1). Iron concentration in plant tissue
at both sampling periods and P tissue concentrations
at harvest were depressed by increased Cu applications.
Copper deficiency symptoms were observed on
plants not fertilized with Cu and were aggravated by
increasing P rate. Copper-deficient young plants ex
hibited symptoms such as rolling and cupping of the
leaves and cessation of terminal growth. At a later
stage, marginal chlorosis developed on young and
mature leaves which progressed towards the base of the
leaves through the interveinal areas. The areas immedi
ately around the leaf vein remained green. At a more
advanced stage, the chlorotic areas became necrotic.
On mature plants, the initial symptom was marginal
leaf chlorosis followed by necrosis.
Effects of P rate. Phosphorus and Cu rates inter
acted in their effects on early yield and on tissue Cu
concentration (Table 2). High rates of Cu with low
rates of P reduced yield. Conversely, high rates of P
with low amounts of Cu also decreased yields. Highest
early yields were obtained with Cu at 8.96 kg/ha and
P at 56 to 112 kg/ha. The highest level of Cu in the
plant tissue was obtained at a Cu rate of 8.96 kg/ha
and with no added P. At all rates of Cu application, Cu
concentrations in the plant tissue were decreased with
TABLE 1.Main effects of copper rates, phosphorus rates, phosphorus sources, and fertilizer
PLACEMENT ON CUCUMBER YIELD AND MINERAL COMPOSITION OF PLANT TISSUES (MEAN OF 1971 AND 1972
SEASONS).
Time of sampling
Total
30 days after planting
At harvest
Treatment
Yield
Cu
P
Fe
Cu
P
Fe
Cu, kg/ha
ton/ha
ppm
%
ppm
ppm
%
ppm
0
11.23
6.0
0.74
138
2.7
0.47
105
2.24
21.37
7.0
0.75
132
3.2
0.42
90
4.48
21.40
7.6
0.75
136
3.2
0.42
81
8.96
24.72
9.4
0.74
134
3.6
0.41
82
F valuef
L**Q**C**
L**
N.S.
C**
L**
L**Q*
L**Q**
P,kg/ha
0
15.81
8.9
0.45
146
3.5
0.24
90
28
21.23
7.2
0.66
136
3.3
0.36
93
56
20.34
6.9
0.78
134
3.1
0.44
86
112
19.88
7.0
0.90
131
2.9
0.56
90
F valuef
C*Q**
L**Q**C**
L**Q**
L**
L**Q**
q*#C**
P source
OSP
21.86a
6.9b
0.79
135
3.3
0.44
91
DAP
19.20b
7.3a
0.76
133
3.2
0.46
91
CSP
19.90b
7.0b
0.79
132
2.8
0.45
86
F valuet
##
##
N.S.
N.S.
N.S
N.S.
N.S.
Placement
Band
16.22
6.7
0.75
139
3.0
0.43
91
Broadcast
23.51
7.8
0.74
131
3.3
0.43
88
F value§
Year
##
##
N.S.
##
##
N.S.
##
1971
11.80
8.4
0.75
129
3.57
0.41
86
1972
27.22
6.0
0.75
141
2.72
0.45
93
F value §
**
##
N.S.
#
N.S.
N.S.
#
fRate effects were linear (L), quadratic (Q), and cubic (C) at the 5% (*) and 1% (**) levels.
Difference between P sources was significant at the 5% (*) level and was separated by orthogonal comparisons or was not significant
(NS).
§Differences between placement and year were significant at the 5% and 1% levels or were not significant.


18
Soil and Crop Science Society of Florida
TABLE 2.Interaction of P and Cu rates on Cu content of
CUCUMBER PLANTS 30 DAYS AFTER SEEDING AND ON EARLY YIELD (1971
AND 1972 POOLED DATA).
P, kg/ha
Cu, kg/ha
0
2.24
4.48
8.96
Mean
Plant Cu, ppmf
0
7.14
8.12
8.24
12.12
8.91
28
5.04
7.07
7.44
9.34
7.22
56
5.44
6.74
7.63
7.74
6.89
112
6.54
6.04
7.12
8.31
7.00
Mean
6.04
6.99
7.61
9.38
Fruit Yield, ton/haf
0
2.79
5.57
7.25
4.22
4.96
28
3.43
10.29
9.15
9.65
8.13
56
4.50
9.70
9.95
10.40
8.64
112
4.08
7.31
8.86
11.93
8.05
Mean
3.70
8.22
8.81
9.05
fP rate effects were linear (L)**, quadratic (Q)**, and cubic
(C)*, and Cu rate effects were L** at the 1% (**) level. Inter
action between P x Cu ** was significant.
fP rate effects were L* and Q**, and Cu rate effects were
L**, Q**, C** at the 5% (*) or 1% (**) level. Interaction be
tween P x Cu** was significant.
an increase in P application. Lowest concentrations of
tissue Cu were obtained with 0 Cu and 28 and 56
kg/ha P.
The main effects of P rate on total yield are shown
in Table 1. Yields were increased significantly with an
increase in P from 0 to 28 kg/ha. With a futrher in
crease in P, yields were slightly reduced. During the
1972 season, effects of Cu and P interacted on total
yield (Table 3). With low rates of either Cu or P and
increased rates of the other element, total yields in
creased quaclratically. However, with high rates of
either element yields increased linearly with an in
crease in the other nutrient. Yields tended to follow
this ¡iattein in 1971, but the interaction was not sig
nificant.
Effect of P source. Application of P from different
sources resulted in significant differences in total yields
and in the Cu concentration in plant tissue 30 days
after seeding and at harvest (Table 1). Total yields
TABLE 3.Effects of P and Cu rates on total cucumber yield
DURING 1971 AND 1972.
Cu, kg/ha
P, kg/ha
0
2.24
4.48
8.96
Mean
1971 yield, ton/haf
0
.75
6.80
10.45
3.22
5.30
28
2.55
12.60
9.40
17.90
10.61
56
2.70
11.05
14.40
15.55
10.95
112
6i50
9.45
10.80
16.15
10.75
Mean
3.59
10.62
11.44
15.22
1972 yield, ton/haf
0
19.75
24.41
31.51
29.61
26.32
28
19.95
37.10
36.71
33.66
31.86
56
19.54
33.54
31.71
34.08
29.72
112
16.81
29.29
30.52
36.47
28.02
Mean
18.87
32.12
31.37
34.23
|P rate effects were linear (L)* and quadratic (Q)**. Cu rate
effects were L** and Q* at the 5% (*) and 1% (**) levels. P x
Cu interaction was not significant.
fP rate effects were cubic (C)**, Cu rate effects were L*#,
Q**, C**. Interaction between P x Cu was significant.
were higher with OSP than with either DAP or CSP.
Yields with the latter two sources were comparable.
There was an interaction between P rate and source in
the 1971 experiment (Table 4). With OSP as the source
of P, there was a linear increase in yield with an in
crease in P rate from 0 to 112 kg/ha. However, with
CSP or DAP, yields were decreased when P rate was
increased above 56 kg/ha. In 1972, yields for the three
sources were 29.5, 31.5, 28.7 ton/ha, respectively, and
were not significantly different.
Tissues concentrations of P and Fe 30 days after
seeding and at harvest were not affected by P sources,
but tissue Cu levels were affected. At 30 days after
seeding, plants grown with DAP contained a signif
icantly higher Cu content (7.3 ppm) than plants grown
with OSP and CSP (6.9 and 7.0 ppm, respectively). At
the harvest stage, differences due to P-source were not
significant.
Effect of fertilizer placement. Cucumber yields dur
ing the two seasons were 45% greater with broadcast
than band fertilizer placement (Table 1). An inter
action between Cu and fertilizer placement signif
icantly affected early and total yields and tissue Cu
concentration (Table 5). Fruit yields and tissue Cu
concentrations increased with an increase in Cu with
both fertilizer placements, but increases were greater
with the broadcast than band placement. Fertilizer
placement had no effect on tissue Cu or yield at the
0 Cu rate.
TABLE 4.Interaction of P source and P rate on total cucum
ber yield, 1971.
Phosphorus
sources
P, kg/ha
28
56
112
Mean
ton/ha
OSP
13.76
11.08
17.83
14.22
DAP
9.54
10.52
9.19
9.74
CSP
8.62
11.26
5.19
8.36
Mean
10.61
10.95
10.75
P rate effects were linear at the 1% level for OSP but not
significant for DAP and CSP.
TABLE 5.Effect of fertilizer placement and Cu rate on the
Cu content of cucumber plants and on early and total fruit
YIELD (1971 & 1972 POOLED DATA).f
Placement
Cu, kg/ha
Cu, kg/ha
0
2.24
4.48
8.96
0
2.24
4.48
8.96
Tissue Cu, ppm
30 days after planting At harvest
Band
5.94
6.58
6.63
7.58
2.64
3.04
3.02
3.16
Broadcast
5.71
6.97
8.33
10.08
2.65
3.36
3.31
3.95
N.S.
N.S.
*
N.S.
N.S.
N.S.
#
Fruit yield, ton/ha
Early
Total
Band
3.14
5.73
5.74
6.27
10.58
17.69
17.34
19.23
Broadcast
4.19
11.13
11.88
13.29
11.90
24.99
26.93
30.21
N.S.
*
#
*
N.S.
#
#
#
fDifferences between placement at a Cu level were not signif
icant (N.S.) or were significant at the 5% (*) level.


19
Proceedings, Volume 39, 1980
DISCUSSION
In both experiments, total encumber yields and Cu
concentrations in plant tissues 30 days after seeding
and at harvest significantly increased with Cu applica
tions. The response of cucumbers to Cu was related to
the low concentrations of native Cu in the soil (less
than 1 ppm Cu extractable with O.UV HC1) and to the
Cu requirements of the crops. Similar responses to Cu
were reported for watermelons (5, 7, II).
High rates of P application with low Cu were re
ported to decrease crop yields and reduce Cu in the
tissue (2, 3, 4). Dekock et al. (3) observed that in
creased application of P increased plant demands for
Cu and under conditions of limited Cu, such enhanced
plant demand could induce Cu deficiency symptoms
and reduce crop yield. In this study, the application of
Cu also enhanced plant demand for P. Thus, yield de
creased with high Cu and with low P rates.
Ordinary superphosphate was found to be a better
source of P for cucumbers compared to DAP or CSP.
Similar results were obtained by Locascio et al. (8) on
watermelons. As shown in Table 4, the superiority of
OSP became more apparent at high rates of P applica
tions. This response may be related to the amount of
other micro or macronutrients in OSP.
In this study, Cu was more efficiently absorbed by
plants when applied broadcast than band; similar re
sults have been reported (11, 12). Interactions between
Cu rate and fertilizer placement were also observed in
this study. In the case of P uptake, banding the fer
tilizers 6.4 cm to the side and 6.4 cm below the seeds
was just as efficient as applying the fertilizers broadcast.
Iron concentrations of the plant tissues were lower with
broadcast placement, not as a result of placement, but
probably clue to high Cu in the plant tissues (13).
Significant correlations were found between total
yields and P on Cu concentration in the plant tissues
30 days after planting and at fruiting time. As shown
in Table 2, adequate P supply and availability in the
soil for cucumbers was indicated by tissue P concen
tration of at least 0.66% (whole plant, dry weight
basis) at 30 days after planting and at least 0.36% (leaf
sample) during the fruiting stage. For Cu, adequate soil
supply was indicated by a tissue Cu level of at least
6.8 ppm (whole plant, dry weight basis) 30 days after
seeding and at least 3.2 ppm (leaf sample) during the
fruiting stage.
LITERATURE CITED
1. Allison, R. V., O. C. Bryan, and J. H. Hunter. 1927. The
stimulation of plant response on the raw peat soils of the
Florida Everglades through the use of copper sulfate and
other chemicals. Florida Agrie. Exp. Sta. Bull. 190.
2. Bingham, F. T., and J. P. Martin. 1956. Effects of soil
phosphorus on growth and minor element nutrition of citrus.
Soil Sci. Soc. Amer. Proc. 20:382-385.
3. Dekock, P. C., M. V. Cheshire, and A. Hall. 1971. Comparison
of the effect of phosphorus and nitrogen on copper-deficient
and -sufficient oats. J. Sci. Food and Agr. 22:437-440.
4. Everett, P. H., S. J. Locascio, and J. G. A. Fiskell. 1966.
Phosphorus and copper effects on growth and yield of water
melons. Proc. Florida State Hort. Soc. 79:155-159.
5. Fiskell, J. G. A., H. L. Breland, S. J. Locascio, and P. H.
Everett. 1967. Effects of phosphate sources on copper and
zinc movement from mixed fertilizers and band placement.
Soil and Crop Sci. Soc. Florida Proc. 27:35-49.
6. S. J. Locascio, and F. G. Martin. 1970. Patterns of
fertilization for watermelon: II. Influence on nutrient dis
tribution in soil and plant uptake. Proc. Florida State Hort.
Soc. 83:149-154.
7. Locascio, S. J., P. H. Everett, and J. G. Fiskell. 1964. Copper
as a factor in watermelon fertilization. Proc. Florida State
Hort. Soc. 77:190-194.
8. P. H. Everett, and J. G. A. Fiskell. 1968. Effects
of phosphorus sources and copper rates on watermelons.
Proc. Amer. Soc. Hort. Sci. 92:583-589.
9. and J. G. Fiskell. 1966. Copper requirements of
watermelons. Proc. Amer. Soc. Hort. Sci. 88:568-575.
10. J. G. Fiskell and H. W. Lundy. 1970. Pattern of
fertilization for watermelons: I. Influence on plant growth
and fruit yield. Proc. Florida State Hort. Soc. 83:144-148.
11. and F. G. Martin. 1972. Influence of
fertilizer placement and micronutrient rate on watermelon
composition and yield. J. Amer. Soc. Hort. Sci. 97:119-123.
12. Navarro, A. A., and S. J. Locascio. 1973. Cucumber response
to copper rate and fertilizer placement. Proc. Florida State
Hort. Soc. 86:193-195.
13. Spencer, W. F. 1966. Effect of copper on yield and uptake of
phosphorus and iron by citrus seedlings grown at various
phosphorus levels. Soil Sci. 102:296-299.
Nitrogen Losses from Urea, Ammonium Sulfate, and
Ammonium Nitrate Applications to a Slash Pine Plantation1
D. B. Boomsma and W. L. Pritchett2
ABSTRACT
Nitrogen transformations and NH3 and NaO losses
were examined following broadcast applications of
urea and (NH4),S04 at 100, 200, 300, and 400 kg N
ha 1 to a 23-year-old slash pine (Finns elliottii var.
elliottii Engelm.) plantation on Wauchula fine sand
(Ultic Haplaquod). A second experiment in the same
general area compared denitrification rates from urea,
(NH4),S04, and NH4N03, applied in solution to the
forest floor at 200 kg N ha-1.
iFlorida Agricultural Experiment Stations Journal Series No.
2260.
sGraduate Assistant and Professor of Forest Soils, respectively,
Soil Science Department, University of Florida, Gainesville, FL
32611.
Rates of NH3 volatilization from urea applied at
400 kg N ha-1 were initially high (>1 kg N ha-1 day-1).
Urea was substantially hydrolyzed within 1 week of
application, resulting in a 1 to 2 unit increase in pH
of soil extracts. Measurements of net accumulation of
NOf indicated little nitrification with either fertilizer
material. Water extracts from urea-fertilized soils had
low concentrations of cations, including NH.,+, com
pared with those from (NH4)2SO.,-treated soils.
If a N2:N20 ratio of 10:1 was assumed, denitrifica
tion losses from urea or (NH4)2S04 represented ap
proximately 1 % of the applied N. If a N2:N20 ratio of
100:1 was used, however, losses from NH4N03 during
100 days following fertilization represented 29% of the
applied N. Volatilization of N following urea or
ammoniacal-N applications does not appear to be a


20
Soil and Crop Science Society of Florida
major pathway of loss in these forest soils and, hence,
leaching is likely to be of greater importance under
most conditions.
Additional Index Words: Forest fertilization, Pine
ecosystems, Nutrient cycling, Denitrification, Cation
loss, Pinus elliottii.
Nitrogen is the nutrient element most frequently
deficient in forest ecosystems. Growth responses to N
and P fertilization in the Southeastern Coastal Plain
have led to operational forest fertilization within this
region. This has occurred in spite of the fact that the
efficiency of N fertilization is often low, due to volatile
losses of NH3 (Volk, 1970), leachinglosses (Sarigumba
et al., 1976; Mead, 1975), and immobilization of ap
plied N (Sarigumba and Fiskell, 1975). Little research
has been conducted on denitrification within forest
ecosystems, even though environmental conditions
often seem to favor this process.
Overrein (1969) and Ogner (1972) reported that
applications of urea to thick humus layers resulted in
microbiological immobilization of urea-N into com
plexes that resisted subsequent mild extraction. The
extent of immobilization of added N appeared to be
in the order urea > NH,C1 > KN03 (Overrein, 1969).
In a review paper, Knowles (1975) suggested that the
additions of 100 ppm of NH.p-N or NO:f-N to the
forest floor may result in large priming effects on
mineralization of organic N to NH.,+, but that the ad
ditions of urea produced only a negligible priming
effect. It was reported that these effects increased with
increasing added N concentrations, but decreased as
temperatures were lowered. Crane (Crane W. 1972.
Urea-nitrogen transformations, soil reactions, and ele
mental movement via leaching and volatilization, in a
coniferous forest ecosystem following fertilization.
Ph.D thesis, Univ. of Washington, Seattle.) reviewed
impacts on cation exchange reactions which followed
the additions of urea to Pacific Northwest forest soils.
These impacts resulted largely from reductions in soil
acidity accompanying hydrolyses of the urea.
After N fertilization, N transformationsespecially
nitrificationmay be inhibited or accelerated by
changes in soil acidity (Alexander, 1977). For example,
applications of urea often decrease soil acidity, whereas
(NH.j)2SO., applications usually increase acidity. Addi
tions of lime with (NH4)2S04 to acid sandy soils re
sulted in nitrification after about 14 days (Eno and
Blue, 1957), but N03~ was not usually found after
fertilization of forest soils. The low levels of N03~ in
forest soils could mean that: (a) nitrification was not
occurring, or (b) N03_ was assimilated by microbes
and higher plants about as fast as it was formed, or (c)
denitrification was as rapid as nitrification, or (d) N03~
was transported vertically or laterally away from the
point of application soon after it was formed.
This study examined certain N transformations
and the extent of gaseous losses due to volatilization of
NH3 and denitrification after application of urea and
(NH4)2S04 to a flatwoods forest soil.
METHODS
The experimental treatments consisted of urea and
(NH4)2S04 at five levels (0, 100, 200, 300, 400 kg N
ha-1) and NH4 NOa at 200 kg ha-1 each replicated three
times in a randomized block design. Individual plots
were 5 x 10 m in size. The study was initiated in June
1978 within a 23-year-old slash pine plantation on a
Wauchula fine sand (sandy, siliceous, hyperthermic
Ultic Haplaquod) near Gainesville, Florida. Ammonia
volatilization measurements were made with four static
diffusion traps per plot, constructed from 4.2-cm diam
eter x 25-cm-long PVC tubes driven through the forest
floor and about 5 cm into the mineral soil. The upper
end of each tube was sealed with a rubber stopper, to
which was attached a glass microfiber paper pretreated
with 4% boric acid. The filter paper was changed on
a schedule as noted below.
Soil was sampled by horizons with a 4.5 cm soil
sampling tube and four cores from each plot were com
posited for each days determination of the treatment
effect. Soil and gas samples were collected 2, 4, 8, 12, 16,
21, 32, 64, and 128 days after fertilizer application. Soil
samples were frozen (10 C) until prepared for ex
traction with deionized water (1:5 ratio). After 1 hour
shaking time, the extract was filtered through millipore
(0.2 micron) units.
Total soil N and water extractable total N were
determined by micro-Kjeldahl (Nelson and Sommers,
1972), after NO, and N03~ were reduced and subse
quently distilled as NH4+ (Bremner, 1965). Urea in soil
extracts was estimated colorimetrically by the method
of Douglas and Bremner (1970). Extract pH was de
termined with a glass-membrane pH-sensitive electrode.
Cations were analyzed by atomic absorption and flame
emission spectrophotometry.
In two smaller experiments designed to compare de
nitrification from applications of urea, (NH4)2S04, and
NH4N03, three gas traps, constructed from 25-cm-
diameter PVC cylinders and driven 10 cm into the
surface soil, were placed in each treatment plot. Traps
remained open until sampling days when they were
sealed with plexiglass sheets against latex rubber rings
for 1 hour prior to sampling. Gas samples were col
lected periodically, through the plexiglass lid via serum
stoppers, and N,0 content of these samples determined
by gas chromotography with a N:65 electron capture
(EC) detector. Total denitrification was estimated by
multiplying the N20 concentration by the ratio of
N2-N:N,0-N of 10:1 (Ryden et ah, 1979; Rolston and
Broadbent, 1977). Precipitation reaching the forest
floor as throughfall was measured by a network of six
rain gauges on the study site (Fig. 1).
RESULTS AND DISCUSSION
The contrasting effects of urea and (NH4)2S04
fertilizers on soil pH are shown in Table 1. Applica
tions of (NH4)2S04 increased soil acidity by about half
a pH unit and this change in acidity persisted for
about 30 days after fertilization, during which there
were about 50 cm of rainfall. On the other hand, urea
fertilizer applications resulted in decreased acidity of
as much as two pH units and some changes in pH
persisted for 128 clays after fertilization.
Ammonia volatilization from the urea treatments
amounted to only 2 to 3% of the applied N over the
128-day period. Losses from (NH4)2SO., treatments
were much lower. Ammonia losses decreased exponen
tially with time after treatment. Although there was a
statistically significant effect of time and treatment on


Proceedings, Volume 39, 1980
21
20 40 GO 80 100 120
Fig. 1.Daily and cumulative rainfall collected beneath tree
canopy.
daily and cumulative NH¡¡ volatilization, the gross
amounts lost represented only a small percentage of
fertilizer N applied (Fig. 2 and 3).
Movement of N into the upper part of the mineral
soil prior to, or following, transformations was mark
edly affected by rainfall events. Daily and cumulative
TABLE 1.Water extract pH of forest floor (FF) and A1
horizons.
Fertilizer sources and rates (kg N ha-i)
Control Ammonium sulfate Urea
Days after 0 200 400 200 400
treatment FF Al FF A1 FI Al FF AI FF M
2 4.15 4.56 3.57 4.21 3.55 4.31 5.84 4.98 5.76 4.93
4 4.10 4.70 3.56 4.29 3.58 4.19 5.16 4.78 6.31 5.28
12 4.16 4.46 3.81 3.97 3.82 4.14 5.21 4.71 5.91 5.20
32 4.18 4.30 4.05 4.14 4.36 4.37 4.57 4.32 5.68 4.91
128 4.03 4.26 3.83 4.14 3.84 4.20 4.22 4.31 4.62 4.33
Time Since Feutiuz ation. (dam's)
Fig. 2.Daily ammonia volatilization.
O ZO 40 120
time since fEuriuzATioN (days)
Fig. 3.Cumulative NH^-N losses from nitrogen application.
rainfall for the duration of soil sampling are shown in
Fig. 1. Nitrogen (NH,+) from (NH4)2S04 appeared to
be more mobile than N from urea in this soil (Table
2). A possible explanation was the increased effective
exchange capacity brought about by the rise in pFI as
the urea hydrolyzed. Increased CEC enabled more of
the hydrolyzed urea to remain in the surface layers as
exchangeable NH4+. Another, and possibly more po
tent, effect was the presence of a strong anion (S04=)
in the (NH4),S04-treated soils. Because S04= ions are
only weakly adsorbed, they were available to leach with
the NH/.
In addition to the NH/, larger concentrations of
basic cations (Ca2+, Mg2+, K+, and Na+) were adsorbed
as a result of the increased effective CEC following
urea fertilization. Table 3 shows that total cations in
water extracts of this soil were low for urea-treated
samples, while (NH4)2S04 resulted in significant in
creases in total cations initially in solution, which
persisted through 12 days (or 75 mm of rain).
TABLE 2.Concentrations of NH -N in water extracts of the
4
forest floor during 128 days following fertilization with 400
kg N ha-i from ammonium sulfate and urea.
Time
Nitrogen source
since
Ammonium
treatment
sulfate
Urea
days
2
7605
2325
4
3640
704
8
4375
1114
16
1675
613
32
303
424
64
52
140
128
5
165


22
Soil and Crop Science Society of Florida
TABLE 3-Total cations (AW, Ca2+, Mg2' K1+, Nai+) in water
EXTRACTS OF FOREST FLOOR (TT) AND A1 HORIZONS.
Days
after
treatment
Fertilizer sources and rates (kg N ha-1)
Control Ammonium sulfate Urea
' 200 400 200 400
FF Al FF Al FF Al FF Al FF A1
/tg g-1 ODW
2
694
26
934
30
3101
35
180
25
315
25
4
444
19
1444
28
1990
39
190
25
180
11
12
425
15
851
43
1182
24
223
19
219
16
32
441
26
451
36
384
27
216
31
136
18
128
320
18
404
16
339
17
350
16
230
15
The increased pH which resulted from urea fer
tilization was expected to enhance conditions for
nitrification. Although little or no NO," + N03- was
detected in soil samples for the duration of the field
experiment, there appeared to be some minor trans
formation to N02- + N03" early in the sampling
period. This was indicated by the 1 to 3 kg N03-N ha-1
found in the A1 horizon at 2 to 4 days after fertilizing
with (NH4)2S04 or urea and the small increase in N,0
losses (Table 4). The low level of N03" in the soil does
not necessarily imply that nitrification was not taking-
place; it could mean that re-assimilation, leaching, or
denitrification depleted NO," + N03" almost as rap
idly as they were formed.
Denitrification certainly occurred, as indicated by
evolution of N,0, but it should be stressed that the
total gaseous evolution of N,0 was small. Applications
of ammonium sulfate at 400 kg N ha-1 resulted in a
maximum evolution of about 8 g N,0-N ha-1 day-1.
Urea at the same rate resulted in considerably higher
levels of N20, following an incubation phase (in the
soil), and immediately after a storm event (Fig. 4).
Total denitrification losses, which included N2 as
well as N,0, were doubtlessly considerable greater than
the levels indicated by N20-measurements alone. Be
cause of equipment limitations, only N,0 losses were
measured, even though much greater quantities of N2
than N,0 were assumed to have been lost. The as
sumed N:N,0 ratio of 10:1, mentioned previously,
TABLE 4.Nitrous oxide losses following applications of
NITROGEN FERTILIZERS TO A FOREST FLOOR.
Fertilizer sources and rates (kg N ha-1)
Days
after
Control
Ammonium
sulfate
Urea
Am
monium
nitrate
treatment
0
200 400
200 400
200
1
1.2
0.0
2
2.2
1.9
0.6
1.5
3
1.7
2.6
3.0
3.6
4.1
1.4
9
4.7
6.8
5.0
6.9
7.1
1.4
15
1.8
2.4
3.1
2.1
2.5

17
2.6
5.2
4.1
2.5
2.9
8.5
29
1.1
1.5
7.6
1.5
1.2
11.1
56
0.1
0.0
0.0
0.0
26.6
7.2
57




52.8
8.4
60
0.2
0.6
0.0
1.5
16.8
4.2
62
1.2
0.6
1.3
2.1
12.1

68
1.4
2.9
1.5
1.9
11.3

74
1.8
1.6
2.8
2.3
8.9

76
0.7
0.0
0.7
0.4
9.9
8.0
108




4.8

Fig. 4.Daily N O from urea and ammonium nitrate.
was supported by unpublished work of Krottje (per
sonal communication) who measured ratios from 10:1
to >100:1 in incubation studies. Therefore, for the
purposes of estimating total denitrification losses, a
ratio of at least 10:1 seemed appropriate. Table 4 lists
denitrification losses of N20 from various N fertilizers
and rates, expressed as grams per hectare of N,0-N per
day. Losses by denitrification were not significant for
(NH4),S04 (except for one event) nor for urea applied
at 200 kg N ha-1. Urea at 400 kg N ha-1 and NH, N03
applied at 200 kg N ha-1 (100 kg N03--N ha-1) resulted
in significantly more denitrification than either
(NH4)2S04 at 400 kg ha-1 (Table 4) or urea applied at
200 kg N ha-1 (Fig. 4).
Since (NH4),S04 and NH,,N03 were applied at the
same time and only NH,NO;i resulted in denitrifica
tion, the role of NOp availability in controlling the
rates of denitrification in this soil was confirmed. High
est levels of denitrification in these experiments were
50 g N,0-N ha-1 day-1, with background rates of 1 to
2 g NoO-N ha-1 day-1. These high rates of loss were
ephemeral, lasting for 1 to 2 days only, with inter
mediate rates persisting for 10 to 60 days. On the other
hand, Rolston and Broadbent (1977), working with a
fertilized agricultural soil, measured peak losses close
to 50 kg N2-N ha-1 day-1, arising from the fertilizer
applied.
CONCLUSIONS
Urea hydrolysis was rapid and subsequent NH3
volatilization amounted to only approximately 3% of
applied N.
Nitrate levels in the soil were very low throughout
the experimental period, despite the reduction in soil
acidity after urea applications.
Water-extractable NH/, Ca++, Mg++, K+, and Na*
decreased after fertilization with urea. This decrease
likely resulted from increased cation exchange capacity
brought about by the higher soil pH associated with
urea applications. Ammonium sulfate applications re-


23
Proceedings, Volume 39, 1980
suited in increased acidity and concurrent increases in
NHt* and other cations in solution.
A large part of the exponential decline in NH3
volatilization and concentrations of cations in soil ex
tracts following fertilization was related to cumulative
rainfall.
The low NO:1~ levels were thought to result from
low nitrification, rapid assimilation by microbes and
higher plants, denitrification, and leaching; but low
nitrification was probably the principal cause.
Estimated total denitrification, based on measured
N20 fluxes and an estimated N2:N20 ratio of 10:1, re
sulted in low N losses. Losses from urea, applied at 400
kg N ha-1, were only about 1% of the applied N. If,
however, a N2:N,0 ratio of 100:1 is assumed (which is
within the range of reality), up to 29% of applied
NH4N03 would have been lost during 100 days follow
ing fertilization. Nevertheless, leaching losses stemming
from frequent tropical summer storm events, rather
than gaseous losses, are likely to be responsible for a
major part of the unaccounted-for N from fertilization
of similar pine ecosystems.
ACKNOWLEDGMENT
The assistance of Owens-Illinois, on whose prop
erty the experiments were located, is acknowledged.
LITERATURE CITED
Alexander, M. 1977. Introduction to Soil Microbiology. 2nd ed.
John Wiley and Sons, Inc., New York.
Bremner, J. M. 1965. Inorganic forms of nitrogen, p. 1179-1237.
In C. A. Black (ed.) Methods of soil analysis. Agronomy 9.,
Am. Soc. of Agron., Madison, Wis.
Douglas, L. A., and J. M. Bremner. 1970. Extraction and
colorimetric determination of urea in soils. Soil Sci. Soc. Am.
Proc. 34:859-862.
Eno, C. F., and W. G. Blue. 1957. The comparative rate of
nitrification of anhydrous ammonia, urea, and ammonium
sulfate in sandy soils. Soil Sci. Soc. Am. Proc. 21:392-396.
Knowles, R. 1975. Interpretation of recent 15N studies of nitrogen
in forest systems, p. 53-65. In B. Bernier and C. H. Winget
(ed.) Forest 'Soils and Forest Land Management. Laval Univ.
Press, Quebec.
Mead, D. J., and W. L. Pritchett 1975. Fertilizer movement in a
slash pine ecosystem II. N distribution after two growing
seasons. Plant Soil 43:467-478.
Nelson, D. W and L. E. Sommers. 1972. A simple digestion pro
cedure for estimation of total nitrogen in soils and sediments.
J. Environ. Qual. l(4):423-425.
Ogner, G. 1972. Changes in the composition of raw humus and
the transport of organic matter as a result of urea fertiliza
tion. Proc. Int. Meet. Humic Substances, Nieuwershuis, Pudoc,
Wageningen.
Overrein, L. N. 1969. Lysimeter studies on tracer nitrogen in
forest soil: 2. Comparative losses of nitrogen through leaching
and volatilization after the addition of urea-, ammonium-,
and nitrate-i^N. Soil Sci. 107(3): 149-159.
Rolston, D. E., and F. E. Broadbent. 1977. Field measurement of
denitrification. Environ. Protect. Tech. Series. EPA-600/2-77-
233, U.S. EPA, Ada, Oklahoma.
Ryden, J. C., L. J. Lund, J. Letey, and D. D. Focht. 1979. Direct
measurement of denitrification loss from soils: 11. Develop
ment and application of field methods. Soil Sci. Soc. Am. J.
43:110-118.
Sarigumba, T. I., W. L. Pritchett, and W. H. Smith. 1976. Urea
and ammonium sulfate fertilization of potted slash pine under
two soil moisture regimes. Soil Sci. Soc. Am. J. 40:588-593.
Sarigumba, T. I., and J. G. A. Fiskell. 1975. Urea transformations
in two acid sandy soils. Soil Crop Sci. Soc. Florida Proc. 35:
150-155.
Volk, G. M. 1970. Gaseous loss of ammonia from prilled urea
applied to slash pine. Soil Sci. Soc. Am. Proc. 34(3):513-516.
Profile Distribution of Phosphate and Metals
in a Forest Soil Amended with Garbage Compost1
J. G. A. Fiskell and W. L. Pritchett2
ABSTRACT
Soil profile samples were taken from plots of
Myakka-Basinger fine sand that had received 0, 65, 130,
and 260 metric tons/ha of Gainesville municipal
garbage compost 2 years previously, applied either
broadcast and bedded or in the planting furrow. In
organic P, organic P, and metal distribution were de
termined. About 50% of the applied inorganic P was
converted to organic P and remained in the zone of
compost placement. Lack of P mobility was attributed
to adequate Fe and A1 in the soil surface horizons and
to additional Fe and A1 supplied in the compost.
Metals extracted by hot 0.1 N HC1 were primarily
distributed in the 0 to 23-cm depth; this coincided with
the distribution of course glass indicative of compost
placement whether broadcast or in the planting fur
row. At depths below 23 cm, metal levels from compost
treatments rarely exceeded those at corresponding
iFlorida Agricultural Experiment Stations Journal Series No.
2171.
^Professors, Soil Science Department, University of Florida,
Gainesville, Florida 32611.
depths of the control plots. At each rate of compost
amendment, the profile distributions were similar for
P, Cd, Cu, Mn, Pb, and Zn. Coarse material > 2mm
also contained high levels of these metals. There were
indications that roots in subsoil of the compost-treated
plots were higher in some metals than roots in control
plots.
Additional Index Words: Inorganic P, Organic P,
Metal mobility, Waste disposal, Nutrient movement,
FI a two od forests.
Recycling of municipal garbage compost in order
to reclaim nutrients otherwise lost in landfills has not
become a popular practice mainly because unsightly
residues or disagreeable odors create an unfavorable
impression on nearby residential areas. Such objections
can be largely avoided by applications of the compost
to more remote land planted to forest where residues
can be reduced by incorporation in the planting beds
and subsequently covered by forest litter. Where this
practice has been used (2, 4), weed growth and under
story shrub growth competed strongly with the


24
Soil and Crop Science Society of Florida
planted pine during the first 5 years. Nevertheless, in
such a planting at the Austin Carey forest near Gaines
ville, both tree height and diameter increased more
rapidly where garbage compost had been applied than
in the control plots (4). During this period, levels of
N, P, and metals in the pine foliage increased linearly
with rate of compost application. However, there were
few differences between surface broadcast and bedding-
compared to placement in a planting furrow and then
bedding (4). The present study determined the
amounts and distribution of P and metals from the
garbage compost that remained in the soil profile after
8 years.
MATERIALS AND METFIODS
The experiment was conducted at the Austin Carey
forest near Gainesville. The cleared forest site was
composed of Myakka (sandy, siliceous, hyperthermic
Aerie Haplaquod) and Basinger (sandy, siliceous,
hyperthermic Spodic Psammaquent) fine sands in
which the degree of development of the Bh horizon
was a principal difference between the two series. Both
soils had an initial soil pFI ranging from 4.3 to 4.5.
The municipal garbage compost (58% moisture) was
obtained from the Gainesville, Florida, plant and was
either spread broadcast over the plot (each 0.081 ha)
with subsequent disc incorporation into four planting
beds (BD) or was placed in planting furrows over
which beds were contructed (IF). The rates were 65,
130, and 260 dry metric tons per hectare (mt/ha) in
three randomized blocks, each consisting of the six
treatments and a control. Year-old slash pine seedlings
were planted 5 months after compost amendment in
rows 3 m apart.
At 8 years after treatment, soil samples were taken
using a hydraulic-driven tube with a 7.7 cm diameter
located at the bed center between trees. Three cores
taken per plot were combined for the 0 to 8 cm, and
subsequent 15-cm depths to a depth of 83 cm, and kept
in polyethylene bags. The samples were processed
through a 2-nnn sieve. Coarse compost residue and
roots remaining on the sieve were dried, weighed, and
ashed at 350 C for 90 minutes followed by heating at
550 C for 90 minutes. The ash was weighed and dis
solved in IN HC1 and analyzed for metals by atomic
absorption spectroscopy.
The soil passing the sieve was air-dried and mixed
on a plastic sheet. To determine inorganic P, 5-g sub
samples were placed in 50 ml of 0.1IV HC1 in Pyrex
tubes, heated in a water bath at 98 C for 3 hours, then
filtered through No. 42 Whatman paper, and washed
with a further 50 ml of hot 0.LV FIC1 as proposed by
Saunders and Williams (6). For organic P, the paper
was washed several times with water and then trans
ferred to 200 ml of 0.1IV NaOH and shaken inter
mittently at 20 C for 16 hours. A 20-ml aliquot was
pipetted into a 150-ml beaker and evaporated to dry
ness. Acid digestion of the sample proceeded in a suit
able fume hood with 1 ml of perchloric acid and 10 ml
of concentrated HN03 heated until all organic matter
disappeared, and where organic matter persisted, addi
tional HN03 and a few drops of 30% H202 were
added for complete digestion. The sample was diluted
with 50 ml of water, titrated with 0.1N NaOH to pH
3 and analyzed for P by the ascorbic acid molybdate
method. This P fraction has previously been reported
as organic P (1,6).
Other 5-g soil samples were ashed at 350 C for 2
hours and at 500 C for 2 hours in crucibles which then
received 2 ml concentrated HN03 at low heat. Transfer
of ash to filter paper was made with 0.2N H2S04 in
repeated rinsings, and the filtrates made to 100-ml
volume. These solutions were analyzed for total P by
the above colorimetric method and the difference be
tween total P and inorganic P was also termed
organic P (3). To confirm the completeness of P re
covery, many of the residues from the ashed samples
received 0.5 g Na2C03, prior to reashing at 550 C.
These were ground in a mortar and then 0.5 g of the
sample was fused with 5 g of Na2C03 in a Pt crucible.
The melt was dissolved in LON HC1 made to 100 ml
volume in 0.1 Ar HC1 and analyzed for P, Ca, Al, and
Fe.
Metal contents of the O.llV HC1 extracts and the
0.2N H,S04 extracts were determined by atomic ab
sorption or using the graphite furnace HGA 2100 and
Perkin-Elmer 503 unit where necessary for greater
accuracy at low Cel and Cu values. Data were statistic
ally analyzed for effect of rates and placement on P
and metal values with depth and comparison of meth
ods for determination of organic P.
RESULTS AND DISCUSSION
Municipal garbage compost at the rates used in this
study (Table 1) added high levels of N, P, and metals.
Both slash pine and under- story species showed ob
vious response to compost addition, particularly to the
intermediate rate during the first few years (2) and
good response was noted in other species (5). However,
only a small portion of the nutrients added was in
volved in plant uptake, because heavy metal com
pounds in soils have low solubilities. The remainder
was probably present in various unavailable forms.
Factors expected to influence P and heavy metal move
ment from the site of compost placement were time,
soil acidity, and formation of water-soluble ions and
complexes. At soil pFI 5.0 (4) and after 8 years, soil
samples taken below the zone of compost placement
should contain P or metal accumulations if leaching
occurred, and be expected to concentrate in the Bh
TABLE 1.Composition of Gainesville municipal garbage com
post AND AMOUNTS OF ELEMENTS ADDED PREPLANT TO MYAKKA-
BASINCER SOIL AT AUSTIN CAREY FOREST.
Composition Compost added, mt/ha
Component
Content
65
130
260
ppm
kg/ha
Soluble salts
1,450
95
189
377
Total N
7,100
462
923
1,846
Inorganic P
1,730
113
225
450
Organic P
336
21
43
87
Al
6,550
425
850
1,700
Fe
4,600
300
600
1,200
Ca
19,100
1,242
2,483
4,966
Mg
1,700
112
221
442
K
2,300
150
299
598
Cd
42
2.7
5.5
11
Cu
155
10
20
40
Mn
328
21
43
85
Ni
68
4.5
9
18
Pb
613
40
80
159
Zn
985
64
128
256


25
Proceedings, Volume 59, 1980
horizon. Since a large amount o£ energy was supplied
in compost material for heterotropic organisms, avail
ability of both P and heavy metal compounds could be
expected to be altered by microbial processes. However,
the effect of microbial immobilization on leaching is
unknown.
Phosphate: Conversion of inorganic P supplied by
the compost (Table 1) to organic P forms indicated
microbial incorporation had occurred (Table 2). The
direct method for organic P (as determined in cold
0.1 A NaOH extracts) showed a very high correlation
(r = 0.97 or better) at each soil depth to that found
by the indirect method obtained by the difference be
tween total P of ashed samples and that extracted by
hot 0.1 A HC1 extraction. The indirect method always
gave from 1 to 2 ppm of P more than that found by the
direct method. This is a rather small difference con
sidering the magnitude of P values in Table 2. This
is in contrast to greater differences between these meth
ods found for other soils (3, 7).
There were no significant increases from treatment
either in inorganic P at depths below 38 cm or in or
ganic P at depths below 23 cm. Since the spodic horizon
was generally located at 53 to 68-cm depth, any move-
TABLE 2.Inorganic and organic P distributions in sandy soil
PROFILES SAMPLED 8 YEARS AFTER MUNICIPAL GARBAGE COMPOST
AMENDMENT.
Garbage compost rate and placement, mt/haf
Depth
0
65
65
130
130
260
260
sampled
BD
IF
BD
IF
BD
IF
cm
kg/ha
Inorganic P¡¡¡
0-8
14
38
40
65
21
61
157
8-23
18
117
221
275
38
60
94
23-38
15
52
57
21
30
35
33
38-53
38
35
28
23
15
20
33
53-68
26
28
32
25
27
33
53
68-83
31
24
32
27
20
33
38
Profile
142
294
410
436
151
242
408
Organic P§
0-8
21
- 42
36
53
24
52
186
8-23
25
54
182
192
42
52
68
23-38
27
42
47
28
32
28
45
38-53
76
36
42
32
36
48
56
53-68
56
67
44
39
80
75
84
68-83
37
44
37
34
28
38
38
Profile
242
285
388
378
242
293
477
Recovered P
0-8
35
80
76
118
45
113
343
8-23
43
171
403
467
80
112
162
23-38
42
94
104
49
62
63
78
38-53
114
71
70
55
51
68
89
53-68
82
95
76
64
107
108
137
68-83
68
68
69
61
48
71
76
Profile
382
579
798
814
393
535
885
Applied P
134
134
268
268
537
537
Recovered PControl P
197
416
432
11
153
503
+BD is broadcast and bedded and IF is placement in furrow
before bedding.
¡¡¡Determined by hot 0.1 A1' HC1 extraction.
(¡Determined sequentially by cold 0.11V NaOH extraction.
ment of P from the upper surfaces should have re
sulted in P accumulation at this depth. However, there
was no evidence of any such accumulation. Amounts
of A1 and Fe throughout the profile (Table 3) were
probably sufficient to sorb P. From comparison of total
P recovered from the soil profile (Table 2) to that
applied, it is obvious that soil samples diet not ac
curately reflect the compost rate and placement treat
ment. This was attributed to lack of uniformity during
compost spreading and to difficulty in positioning the
power sampler exactly at the center of the bed. The
inorganic to organic P ratio at the 0 to 8-cm depth was
0.69 in the control plots compared to a range from
0.85 to 1.23 for amended soil. At the 8 to 23-cm depth,
corresponding rates were 0.72 for the control and a
range from 0.89 to 1.43 for treated soil. It was evident
that conversion of inorganic P to organic P had oc
curred over an 8-year span and that this P showed
little evidence of mobility in contrast to preferential
organic P mobility reported in other soils (7).
Since effect of compost placement on inorganic P
was independent of compost rate at the 0 to 8-cm
depth, the significant (0.05 level) rate effect on in
organic P was found to be
P= 5.23 + 20.8 R [1]
where R is compost rate/65 mt/ha. However, at the 8
to 23-cm depth both inorganic and organic P were
found to have significant quadratic responses to rate
of compost within the rate X placement interaction.
Locating compost placement: Further explanation
for the variability in P data was obtained by examining
the distributions of Fe, Al, Ca, and crushed glass
(Table 4). At the 0 to 8-cm depth, Ga significantly in
creased with compost rate:
Ca = 7.17 + 360.4 R, [2]
whereas at the 23 to 38-cm depth, Ca decreased signif
icantly with compost rate:
Ca = 405 67.2 R. [3]
This may be explained by deeper placement at the
lower rates than at the higher rates, suggested by the
large differences in Ca at the shallower depths in the
six treatments. The Al and Fe values in the 0 to 23-cm
depths showed similar pattern of changes in magnitude
as those for Ca. For instance, at the 8 to 23-cm depth,
Fe values also decreased with compost rates:
Fe = 521 -79.5 R. [4]
Presence of crushed glass accounted for the major
differences in ash from the coarse soil fraction (Table
4), with values always being highest at the shallower
depths. This coarse glass associated with the compost
was present where coarse ash exceeded 2.5 g/kg soil,
magnitude of changes at 0 to 38-cm depth being like in
pattern to those for other components (Tables 4 and
5). Grams of coarse ash (AW) for the whole composite
core sample resulted in highly significant response for
the placement X rate interaction. For BD placement,
the relationship was
AW = 130 + 292 R 61 R2. [5]
For IF placement it was
AW = 401 + 270 R + 46 R-, [6]
, r
whereas corresponding ash weight for the control at


26
Soil and Crop Science Society of Florida
TABLE 3.Dominant soil series organic matter, total Fe and A1 in control and compost-
amended PROFILES.!'
Depth
sampled
Horizon
Organic matter^
Fe§
Al§
0
260 mt/ha
0
260 mt/ha
0
260 mt/ha
cm
_ %
Myakka fine sand
0-8
Ap
1.44
3.80
132
2,550
260
3,800
8-23
Ap
2.67
2.01
146
270
140
480
23-38
A22
1.32
1.35
148
110
460
620
38-53
B21h
1.91
0.86
194
71
2,680
2,750
53-68
B22h
0.86
1.58
152
240
1,480
2,000
68-83
C
0.66
1.25
148
130
1,800
1,450
Basinger fine sand
0-8
Ap
1.32
1.78
132
460
300
2,050
8-23
Ap
1.65
1.65
146
690
300
2,400
23-38
A22
0.83
0.96
144
290
460
1,550
38-53
C & Blh
0.83
0.96
260
270
1,500
1,910
53-68
C & B2h
0.74
0.92
124
150
740
860
68-83
C2
0.60
0.73
54
92
940
650
fMean for 3 replicates of composite cores sampled from center of the bed.
^Determined by dichromate- concentrated H SO oxidation.
§Determined after concentrated HN03
digestion and 0.2N H2S04 extraction of soil ashed at 550C.
TABLE 4.-
-Distribution
of Fe, A1 Ca,
AND COARSE ASII IN
SANDY SOIL 8
YEARS AFTER
MUNICIPAL
GARBAGE COMPOST AMENDMENTS.
Garbage compost rate and placement, mt/ha
S.E.
Depth
65
65
130
130
260
260
of
sampled
0
BD
IF
BD
IF
BD
IF
mean
cm
Fe, ppmf
0-8
139
285
173
184
159
287
343
61
8-23
100
440
440
540
187
245
159
56
23-38
68
293
246
118
165
121
147
49
38-53
55
147
41
95
139
89
95
39
53-68
43
102
65
87
100
77
129
23
68-83
61
79
43
58
81
55
87
12
Al, ppmf
0-8
227
410
267
274
540
567
940
129
8-23
187
373
540
720
550
440
300
90
23-38
433
313
353
370
730
421
627
125
38-53
1,680
880
880
693
970
767
740
183
53-68
1,510
1,630
1,220
653
850
900
960
191
68-83
960
1,130
1,000
647
635
653
567
162
Ca, ppmf
0-8
156
593
553
653
235
713
2,370
292
8-23
93
813
1,270
1,570
267
487
387
88
23-38
46
331
417
190
246
123
187
04
38-53
30
65
132
90
39
49
87
17
53-68
10
49
70
86
29
33
133
28
68-83
25
19
35
31
14
67
62
14
Coarse ash, g/kg soil
0-8
2.5
10.6
7.9
3.1
4.9
7.1
7.0
8-23
1.8
20.0
15.1
10.8
3.7
12.8
3.9
23-38
1.0
10.1
7.0
7.4
3.5
3.3
2.2
38-53
1.3
2.9
1.9
0.5
0.5
1.8
0.9
53-68
0.8
2.0
2.0
0.9
0.5
0.7
0.7
68-83
1.1
0.4
2.4
0.4
0.2
1.0
0.8
fExtracted by hot O.hV HC1 for 3 hours.


27
Proceedings, Volume 39, 1980
TABLE 5.Metal distributions in sandy soil sampled 8 years
AFTER MUNICIPAL GARBAGE COMPOST AMENDMENTS.>¡*
Depth
sampled
Garbage compost, mt/ha
S.E.
of rate
mean
0
65
130
260
Zinc
0-8
5.8
41.5
34.7
44.6
31.7
8-23
4.3
80.0
124.0
25.3
12.4
23-38
4.7
32.9
5.8
6.8
7.3
38-53
3.3
6.3
5.9
3.3
0.9
53-68
5.0
11.0
6.1
4.4
4.2
68-83
7.0
7.9
7.4
5.4
1.8
Copper
0-8
0.48
4.33
128.00
15.90
3.72
8-23
0.80
7.27
12.90
2.88
0.44
23-38
0.43
1.19
0.85
0.79
0.09
38-53
0.58
0.53
0.61
0.47
0.01
53-68
0.48
0.53
0.76
0.71
0.04
68-83
0.37
0.55
0.89
0.06
0.01
Cadmium
0-8
0.063
1.730
2.070
0.933
0.61
8-23
0.047
1.088
4.600
0.306
1.18
23-38
0.051
0.751
0.057
0.047
0.44
38-53
0.031
0.040
0.028
0.004
0.01
53-68
0.073
0.045
0.069
0.004
0.02
68-83
0.053
0.035
0.007
0.005
0.01
Manganese
0-8
2.3
24.9
15.4
18.6
11.73
8-23
0.7
23.3
47.3
8.8
3.60
23-38
0.7
6.9
1.8
1.3
1.89
38-53
0.7
1.0
1.9
0.8
0.51
53-68
0.5
0.8
1.5
0.7
0.98
68-83
0.7
0.7
0.6
0.7
0.26
Lead
0-8
0.10
31.30
20.00
48.00
12.30
8-23
0.01
41.70
62.70
16.70
8.08
23-38
0.01
23.30
7.40
0.70
6.46
38-53
0.01
0.01
0.10
0.10
0.07
53-68
0.01
0.01
0.01
0.01
0.01
68-83
0.01
0.01
0.01
0.01
0.01
[Determined by hot 0.IN HC1 extraction for 3 hours; BD
samples only shown.
this depth was 11 grams. Failure to obtain a good fit
between treatment application and composite core
data was attributed to (i) differences in compost com
position which was not from a single plant run, (ii)
irregularity in compost spreading, (iii) lack of uni
formity of IF placement, and (iv) difficulty in taking
core samples representative of this variability.
Heavy metals: Heavy metal distributions in the
profile (Table 5) showed increases in metal content at
the 0 to 38-cm depths where compost had been applied
compared to similar depths in the control plots. There
was no statistical difference among values at depths
below 38 cm. Few statistically significant differences
between compost rates were found for any of these
metals because the standard errors for rate means were
relatively high. Only very small amounts of heavy
metals appeared to have moved below the depth of
compost placement. Where compost rate X placement
responses were significant, these occurred at the 8 to
23-cm depth. For BD placement (Table 5), three
metals showed the following significant responses for
rate of compost:
Zn = -26 + 137 R-31 R2, [7]
Mn = -27 + 67 R 14 R2, [8]
and Pb = -41 + 104 R 22 R2, [9]
where R is compost rate/65. Shape of response curves
for Eq. 7-9 was similar to that for ash weight in Eq.
[5], which confirms that sampling did not represent
well the variability for compost placement.
Metals in coarse fraction: In the material > 2mm
designated as coarse material, weight and analyses are
given in Table 6. Roots comprised most of the sample
weight below 38 cm. Contrary to quantity of metals
recovered from the treated soil, roots contained higher
amounts of Cd, Cu, Mn, Pb, and Zn at depths below
38 cm than the soil from control plots, regardless of
TABI.E 6.Metal composition of coarse fraction in sandy soil
PROFILES SAMPLED 8 YEARS AFTER MUNICIPAL GARBAGE COMPOST
AMENDMENTS.!'
Depth
Garbage compost, mt/ha
sampled
0
65
130
260
cm
0.8
Fraction weight, g/kg soil
11.1 16.3 5.0
9.8
8-23
3.4
18.2
16.2
18.1
23-38
1.7
13.3
11.1
5.3
38-53
2.8
4.2
0.9
2.6
53-68
1.1
3.3
1.2
1.1
68-83
1.6
0.7
0.6
1.5
0-8
0.2
Cd, ppm
2.49
4.13
2.36
8-23
0.01
3.48
7.36
7.97
23-38
0.01
6.92
4.01
0.42
38-53
0.01
0.17
0.79
3.05
53-68
0.01
0.56
1.84
0.24
68-83
0.01
2.82
0.12
0.20
0-8
1.6
Cu, ppm
25.8
8.2
123.0
8-23
1.3
38.5
102.0
12.1
23-38
0.6
14.8
8.8
8.8
38-53
0.5
0.9
2.5
4.0
53-68
0.3
1.3
3.5
1.2
68-83
0.2
2.3
0.6
0.7
0-8
17.7
Mn, ppm
35.2
27.5
20.9
8-23
6.0
30.5
65.3
22.2
23-38
3.7
34.7
32.6
1.8
38-53
3.7
2.3
8.9
3.8
53-68
2.0
10.4
11.1
3.5
68-83
1.5
10.5
4.1
2.8
0-8
6.1
Pb, ppm
34.4
71.5
41.0
8-23
4.9
78.9
138.1
57.0
23-38
2.1
209.0
28.8
23.2
38-53
1.5
3.0
32.1
5.6
53-68
0.8
1.3
12.4
4.4
68-83
0.6
1.4
2.9
3.3
0-8
17.5
Zn, ppm
77.4
94.6
77.5
8-23
6.6
193.0
186.0
74.1
23-38
4.6
402.0
142.0
18.7
38-53
3.6
9.7
13.0
20.8
53-68
2.1
14.1
25.1
25.2
68-83
1.5
23.0
2.4
18.3
fCoarse fraction dried at 100 C, ashed at 550 C and dissolved
in HC1.


28
Soil and Crop Science Society of Florida
root weight. This suggested that metals at these depths
were accumulated on or in the roots, perhaps during
mass How of soil solution to the roots. Roots account
for small amounts metals moved below the 38-cm
depth. However, heavy metals present in the coarse
fraction above 38-cm depth were relatively higher than
those shown in Table 5. This suggested that much of
the metal present in the compost had not reacted with
the soil; perhaps much remained in metallic state, as
observed for copper wire in a few samples.
Implication of finding: Soil samples taken at 8
years after compost treatment and those taken 18
months previously (4) showed that very little metal
movement below 38 cm had occurred. However, in the
earlier study with a small diameter tube, metal values
for IF placement exceeded those for BD placement at
0 to 38-cm depths as might be expected, whereas this
was not the case for the larger diameter tube. Con
siderable variability of compost placement was evi
dent, so that monitoring of both P and metal distribu
tion in subsequent years produced problems of within-
plot variation. Other than the lush growth of under
story species competing with pine growth prior to
canopy closure, no adverse effects on forest growth has
been determined. To date, significantly better pine
tree growth has been associated with soil amended with
garbage compost than that in control plots. As forest
litter accumulates, and further reaction of soil and
compost occurs, further monitoring of the site will be
valuable in understanding long-term effects from land
spreading of waste materials on forestlands, and forest
nutrition.
LITERATURE CITED
1. Anderson, G. 1960. Factors affecting the estimation of phos
phate esters in soil. J. Sci. Food Agrie. 11:497-503.
2. Bengtson, G. W and J. J. Cornette. 1973. Disposal of com
posted municipal waste in a plantation of young slash pine:
Effects on soil and trees. J. Environ. Qual. 2:441-444.
3. Dormaar, J. F and G. R. Webster. 1964. Losses inherent in
ignition procedures for determining total organic phosphorus.
Can. J. Soil Sci. 44:1-6.
4. Fiskell, J. G. A., W. L. Pritchett, M. Maftoun, and W. H.
Smith. 1979. Effects cf garbage compost rates and placement
on a slash pine forest and metal distribution in an acid sand,
p. 302-313. In Second Ann. Conf. of Applied Research and
Practice on Municipal and Industrial Waste, Madison, Wis.
5. Hortenstine, C. C., and D. F. Rothwell. 1972. Use of munic
ipal compost in reclamation of phosphate-mining sand tail
ings. J. Environ. Qual. 1:415-418.
6. Saunders, W. M. H., and E. G. Williams. 1955. Observations
on the determination of total organic phosphorus in soil.
J. Soil Sci. 6:254-267.
7. Williams, E. G., and W. M. H. Saunders. 1956. Distribution
of phosphorus in profiles and particle-size fractions of some
Scottish soils. J. Soil Sci. 7:90-108.
Evaporation Effects on Sprinkler Irrigation Efficiencies1
Allen G. Smajstrla and Richard S. Hanson2
ABSTRACT
A numerical simulation model was developed to
study the effects of various sprinkler irrigation manage
ment strategies on crop-water use efficiencies. This
model allows the user to simulate the scheduling of
irrigations for crop production. Model inputs required
are descriptions of climatic, crop, and soil conditions,
specifically including daily rainfall, pan evaporation,
soil-water capacity function, crop effective rooting
zone, and water use coefficients versus growth stage.
This model simulates a daily soil-water balance and
crop-water use, assuming that soil-water contents do
not decrease transpiration rates. In this work, four
levels of soil-water depletion and three magnitudes of
irrigation depths were studied. Seasonal irrigation re
quirements were found to decrease with both greater
allowable water depletions and with smaller depths of
application. This was due to effective rainfall increas
ing with the same components. Seasonal evaporation
losses were found to be unaffected by depth of applica
tions and only mildly affected by decreases in allow
able water depletions. This resulted because evapora
tion rates remained fairly high due to frequent rain
storms.
Gross water requirements were found to be less for
an intermediate application depth, because evapora
iFlorida Agricultural Experiment Stations Journal Series No.
2301.
2Assistant Professor and Student Research Assistant, respec
tively, Agricultural Engineering Department, University of Flor
ida, Gainesville, FL 32611.
tion and interception losses were great for small, fre
quent applications, and because effective rainfall was
low for large, infrequent applications. The optimum
is specific for a given set of soil, crop, and climatic
conditions.
Additional Index Words: Simulation, Computer
model, Evapotranspiration, Effective rainfall.
Sprinkler irrigation efficiencies are always less than
100% because losses occur as water is sprayed through
the air, as water is evaporated from the crop canopy
(interception losses), and as water is evaporated from
the soil surface rather than being transpired by the
crop. Other losses such as those due to deep percola
tion and runoff may reduce irrigation efficiency. How
ever, the latter losses may be completely eliminated by
proper system design and management, whereas evap
oration losses are unavoidable and can only be min
imized by good system management.
The objective of this study was to simulate various
irrigation management strategies for crop, soil, and
weather conditions typical of north central Florida.
Specific data were selected for each of these conditions
because of their unique combination at this location.
Specific objectives of this study included:
1. To develop a numerical model to simulate field
water cycles for irrigated crop production.
2. To determine the effects of soil evaporation, soil
hydraulic properties, and irrigation management
practices on irrigation and water use efficiences.


Proceedings, Volume 39, 1980
29
MATERIALS AND METHODS
A numerical model was developed to simulate the
interactions of the various components of the hydro-
logic cycle for irrigated crop production. Components
of the hydrologic cycle which were simulated by the
model are illustrated in Fig. 1. They included rainfall,
irrigation, evaporation, transpiration, and deep perco
lation.
The numerical model was developed in general
terms so that it would be applicable to studies of irri
gation efficiencies for various crops and soil types. Data
inputs were classified as weather, soil, or crop data.
Weather inputs included daily rainfall and pan evapo
ration data. The soil input was the water capacity
curve. Crop inputs included the functional relation
ships between stage of growth and (1) leaf area index,
(2) effective rooting depth, and (3) water use coefficients.
In this study, sprinkler irrigation efficiency was simu
lated for soybeans (Glycine max (L) Merr.) produced
on Lake fine sand (hyperthermic, coated, Typic
Quartzipsamment) with weather conditions measured
at Gainesville, Florida.
A flow chart of the numerical model is shown in
Fig. 2 (A complete listing of the numerical model is
available from the senior author upon request). Each
simulation began with the input of soil, crop, and
weather data. Those requirements are described in
detail in the following paragraphs.
Leaf area index was calculated in the first compu
tational step. Leaf area index as a function of time was
obtained from studies conducted at the Institute of
Food and Agricultural Sciences (IFAS Irrigation Park
at Gainesville (K. Boote, personal communication).
That function is presented in Fig. 3.
Effective rooting depth was calculated for the ex
isting stage of crop growth. Data of Robertson et al.
(1979) were used to determine maximum depths for
local conditions. Because of the lack of details on root
development versus stage of crop growth, data of
Burch et al. (1978) were also used. Those data are
shown in Fig. 4.
Available soil moisture was calculated as a func-
SOIL- PLANT-ATMOSPHERE SYSTEM
COMPONENTS
Fig. 1.Components of the soil plant atmosphere system
model.
tion of the soil hydraulic properties and effective root
ing depth. The water capacity curve for Lake fine sand
is given in Fig. 5. From this figure, available soil mois
ture on a volumetric basis was estimated. Because of
Fig. 2.Flow chart for the soil plant atmosphere system
model.
Fig. 3.Leaf area index function for soybeans.
Fig. 4.Rooting depth function for soybeans.


30
Soil and Crop Science Society of Florida
the dynamic effects of soil-plant-atmosphere-water in
teractions, available water is not a constant, but is de
pendent upon the interactions of those factors. There
fore, in this work, a range of values was used in order
to study the effects of available water on irrigation
efficiencies. It was assumed that no reduction in crop
growth or yield would occur until after all readily
available soil moisture was depleted. As shown in Fig.
5, the lower limit of the readily available water range
was assumed to occur at approximately 1 bar of capil
lary suction and a volumetric water content of 0.05.
Irrigations were scheduled when all readily available
soil moisture was depleted, so that stress did not oc
cur and production was optimized with respect to
water use.
Evaporation from wet foliage does not greatly ex
ceed normal evapotranspiration rates (Christiansen
and Davis, 1967, and Pair, 1969). It is, however, a func
tion of amount of canopy cover. In this model, inter
ception of rainfall and sprinkler water by the crop
canopy was calculated as a function of leaf area index.
A maximum of 0.25 cm of interception was calculated
for a leaf area index of 6.0 or greater. Interception was
assumed to vary linearly with leaf area index at mag
nitudes of less than 6.0.
Deep percolation losses were calculated from a mass
balance of the water content in the crop rooting zone.
Rainfall depths greater than those necessary to restore
the crop rooting zone to field capacity were assumed
to cause deep percolation, thus becoming unavailable
to the crop.
The soil-water status and effective rainfall were
calculated after each rainfall event. Effective rainfall
was calculated as the total depth of precipitation that
was stored in the crop rooting zone after each rainfall
event. The soil-water status was defined as the depth of
water stored in tire crop rooting zone on a daily basis.
Transpiration rates were calculated on a daily basis
as a function of pan evaporation. Data from National
Weather Service records were used for this purpose.
Crop water use coefficients as a function of time were
VOLUMETRIC WATER CONTENT
Fig. 5.Water capacity function for Lake fine sand.
obtained from SCS Technical Release 21 (1970) and
are given in Fig. 6. Transpiration was assumed to oc
cur at non-water-limiting rates throughout the grow
ing season because irrigations were scheduled when
ever the readily-available soil-water was depleted.
Soil evaporation rates were calculated as a function
of soil hydraulic properties, pan evaporation, and leaf
area index. Ritchie (1972) reported that when the soil
surface is wet, energy at the soil surface and soil-
hydraulic properties limit evaporation. The functions
presented by Ritchie (1972) were used in this work.
Daily evaporation rates were calculated from
Ep = (r/a) ETp, (1)
where Ep = daily evaporation rate for non-water-
limiting conditions (cm/day),
t = dimensionless radiation interception
factor for the crop canopy,
a = dimensionless crop and climate propor
tionality factor, and
ETp = energy-limited ET from a well-watered
surface during non-advective condi
tions.
The numerical value of r was calculated from
r = exp (0.398LAI), (2)
where LAI = leaf area index.
Equation 2 was developed by Ritchie (1972) for
sorghum, and later verified as applicable to soybeans
by Kanemasu et al. (1976). The value of a used was
1.26. That value was established by Priestly and
Taylor (1972) after evaluating 11 different non-advec
tive climatic conditions.
Evaporation from the soil surface was calculated
to occur at the non-water-limiting rate given in Equa
tion 1 through the first stage drying of the soil surface.
First stage drying was assumed to occur for a period of
1 day following rainfall. This assumption was verified
by experimentation at the IFAS Irrigation Park.
After first stage drying, the method of Black et al.
(1969) was used to evaluate losses during falling-rate
stages. For drying of Plainfield Sand, they developed
the following empirical relationship;
E = c/t0-5 (3)
where E = daily evaporation rate (cm/day),
GROWING SEASON (DAYS)
Fig. 6.Soybean growth coefficient function.


31
Proceedings, Volume 39, 1980
c = constant o proportionality for given soil
conditions, and
t = time since beginning of drying cycle (days).
The value of c was defined by Equation 4, which
results from an analytical solution of the one-climen-
sional water flow equation for isothermal flow in a
homogeneous soil-profile (Black et ah, 1969).
c = 2 (Mo) (DA)-5 (4)
where = field capacity volumetric water content,
60 = air dry volumetric water content, and
I) = weighted mean diffusivity (cm2/day).
In equation 4, di for Lake fine sand was assumed to
0.12 (Fig. 5), d was assumed to be 0, and the value of
D was assumed to be 13 cm2/day (Black et ah, 1969).
The value of c was then 0.49 cm/day0-5 for the condi
tions of this study.
The soil-water was updated daily by mass balance,
including evaporation and transpiration depletions.
The decision concerning irrigation scheduling was
made on the basis of the soil-water status. Irrigations
were scheduled when the total soil-water storage in
the plant root zone reached a predetermined critical
level. In this study, four critical levels were investi
gated, and irrigations were scheduled at water deple
tions of 1%, 3%, 5%, and 7% water contents on a
volumetric basis. The 1 % level represented almost
daily irrigations, while the 7 % level represented al
most complete depletion of readily available soil-water.
The 3% and 5% levels were within the range of com
mon irrigation management practices on sandy soils
similar to Lake fine sand.
Three depths of irrigation were simulated to oc
cur. These were 1-cm and 3-cm applications, and a
variable application of sufficient depth to restore the
soil profile to field capacity. These values were chosen
in order to simulate the range the irrigation depths
that could occur. Irrigation interception losses were
calculated as functions of the canopy leaf area index
as rainfall was. Evaporation losses which occur because
water is sprayed through the air are functions of the
evaporative demand and type of irrigation systems used
(Pair, 1969). In this work those evaporation losses were
calculated as 10% of the depth of irrigation (Pair,
1969).
Weather inputs consisted of daily rainfall and pan
evaporation values. Rainfall data were nsecl to update
the soil-water status on a daily basis, and pan evapora
tion data were used on an index of potential evapo-
transpiration and crop-water use. Because rainfall dis
tributions are critical to irrigation management strat
egies, 10 years of daily weather data from National
Weather Service records were used to evaluate the
long-term effects of precipitation distributions for
Gainesville.
RESULTS AND DISCUSSION
The simulation model illustrated in Fig. 2 was
used to study the effects of various irrigation manage
ment strategies on irrigation requirements and water
use efficiency for soybean production on Lake fine sand
at Gainesville, Florida. Actual weather records for a
10-year period of time were used in this study, and all
results are presented as the averages of ten simulated
growing seasons.
Figure 7 illustrates the effects of four water deple
tions and three irrigation application depths required
during the growing season. Smaller applications re
quired more numerous applications. Also, as allow
able water depletions were decreased before irrigations
were scheduled, larger numbers of irrigations were re
quired.
In Fig. 8, the effects of the management decisions
on seasonal soil water requirements are shown. The
greatest amount of water was required to be supplied
at all depletion levels by the practice of replenishing
the entire soil profile to field capacity (NWD prac
tice). This occurred because irrigations at the l-cm and
3-cm levels (below NWD) allowed for storage of some
of the precipitation which occurred immediately after
irrigations. Therefore, rainfall became more effective
in contributing to crop water requirements. Also,
greater amounts of water were restored to the crop
root zone by irrigation as the allowable water deple
tion level was decreased. Again, this occurred because
soil-water contents were always maintained near max
imum levels, and there was little available storage
space for rainfall.
Effective rainfall is that which is stored in the crop
root zone and available for use. In Fig. 9, effective rain
fall decreased with a decrease in allowable water deple
tion. It was also less for those management practices
which replenished all or most of the water deficit in
the crop root zone.
Fig. 7.Simulated number of irrigations as a function of al
lowable water depletion and application depth.
Fig. 8.Seasonal soil water requirements as a function of ir
rigation management practices.


32
Soil and Crop Science Society of Florida
Fig. 9.Effective rainfall as a function of irrigation manage-
ment practices.
Frequent, small applications increased effective
rainfall; however, the soil surface was wet frequently,
and nonproductive evaporation losses also increased.
Figure 10 shows the effects of the factors simulated on
evaporation losses. Because of the frequent, short dura
tion rainstorms common to the Gainesville area, there
was little effect of depth of application on seasonal
evaporation losses. There was a slight increase in
evaporation losses as very frequent irrigations were
scheduled for the allowable water depletions of only
1 %. In those cases the soil surface was almost con
tinuously wet from either irrigation or rainfall.
Irrigation requirements include soil-water require
ments, as well as evaporation, wind drift, and intercep
tion losses during sprinkler irrigation. Those com
ponents were simulated and summed to produce the
results given in Fig. 11. At large allowable water
depletions, irrigation requirements were considerably
greater when the entire soil profile was refilled at each
irrigation than when only a portion of the profile was
restored to field capacity. At lower allowable deple
tions, those differences were less significant. In general,
this occurrence depends upon the soil hydraulic prop
erties and rainfall distributions for the specific site.
In Fig. 11, the NWD treatment required the great
est total amount of water to be pumped, because rain
fall was not used effectively as previously discussed.
The 1-cm treatment required the second-greatest
depths of irrigation because evaporation and intercep
tion losses were great due to the frequent irrigations
and wet soil surface.
Irrigation water use efficiency can be expressed in
several ways. In Fig. 12, water use efficiency was ex
pressed as a percentage, and was calculated as a ratio
Fig. 10.Seasonal evaporation losses as influenced by irrigation
management practices.
Fig. 11.Seasonal irrigation requirements as a function of ir
rigation management practices.
WATER DEPLETION (%)
Fig. 12.Water use efficiency as influenced by allowable water
depletions and application depth.
of water requirements in the plant rooting zone to
rainfall plus water pumped. The best option was the
3-cm water application depth. Further use of this
simulation model would allow further refinement of
the depth of application, although it is apparent that
there is only little improvement to be made over the
range of values studied here. If the 10 years of weather
records are representative of long-term occurrences, it
is apparent that for the sandy soils (and, therefore,
limits on soil water depletion levels) and frequent rain
fall occurrences in the Gainesville area, water use
efficiency can be increased and irrigation requirements
decreased by allowing the soil to act as a reservoir to
increase effective rainfall. At irrigation depths of less
than NWD, irrigation requirements are insensitive to
depth of application.
The conclusions obtained from this study were
based on the criteria of irrigation applications and
water use efficiency only. An optimum irrigation man
agement strategy should be an economic decision, in
cluding such factors as labor costs for frequent small
irrigations versus those for less frequent, larger ones.
The results presented here do, however, provide the
framework for such economic decision model.
Additional research should be directed toward re
fining components of this model. Effects of water de
pletions upon yield reductions should be studied. In
this model it was assumed that irrigations occurred
instantaneously and that yield reductions did not


33
occur due to changes in soil-water content. The range
over which that assumption is valid should be inde
pendently evaluated. Also, the dynamics of soil-water
fluctuations should be included, especially as they in
fluence soil-water and evaporation losses.
SUMMARY AND CONCLUSIONS
A numerical simulation model was developed to
study the effect of various sprinkler irrigation manage
ment practices on crop water use efficiency. This model
allows the user to simulate the scheduling of irriga
tions for crop production. Model inputs required were
climatic, crop, and soil variables, specifically including
daily rainfall, pan evaporation, soil-water-capacity
function, effective rooting zone of the crop, and water
use coefficients versus time.
This model simulated a daily soil-water balance and
crop-water use, with the assumption that soil-water
contents did not decrease transpiration rates. In this
work, four levels of soil-water depletion and three
magnitudes of irrigation depths were studied using 10
years of daily rainfall records for Gainesville, Florida.
Seasonal irrigation requirements were found to de
crease with both greater allowable water depletions
and with smaller depths of application. This was due
to effective rainfall increasing with the same factors.
Seasonal evaporation losses were found to be un
affected by depth of applications and only mildly af
fected by decreases in allowable water depletions. This
was because evaporation rates remained fairly high due
to frequent rainstorms.
Seasonal irrigation requirements were found to be
less for an intermediate application depth, because
evaporation and interception losses were great for
small, frequent application, and because effective rain
fall was low for large, infrequent applications. The
optimum is specific for a given set of soil, crop, and
climatic conditions.
REFERENCES
1. Black, T. A., W. R. Gardner, and G. W. Thurtell. 1969. The
prediction o£ evaporation, drainage, and soil-water storage
for a bare soil. Soil Sci. Soc. Am. Proc. 33:655-660.
2. Burch, G. J., R. C. G. Smith, and W. K. Mason. 1978. Agro
nomic and physiological responses of soybean and sorghum
crops to water deficits. II. Crop evaporation, soil-water de
pletion, and root distribution. Aust. J. Plant Physiology 5:169-
177.
Christiansen, J. E., and J. R. Davis. 1967. Sprinkler irrigation
systems, p. 885-904. In R. M. Hagan, H. R. Haise, and T. W.
Edminster (Ed.). Irrigation of Agricultural Lands. Am. Soc.
Agron. Madison,Wis.
4. Kanemasu, E. T L. R. Stone, and W. L. Powers. 1976. Evapo-
transpiration model tested for soybean and sorghum. Agron.
J. 68:569-572.
5. Pair, C. H. 1969. Sprinkler Irrigation. Sprinkler Irrigation
Assn., Washington, D. C.
6. Priestly, C. H. B., and R. J. Taylor. 1972. On the assessment
of surface heat flux and evaporation using large-scale param
eters. Mon. Weather Review. 100:81-92.
7. Ritchie, J. T. 1972. Model for predicting evaporation from
a row crop with incomplete cover. Water Resour. Res. 8:1204-
1213.
8. Robertson, W. K., L. C. Hammond, J. T. Johnson, and G. M.
Prine. 1979. Root distributions of corn, soybeans, peanuts,
sorghum, and tobacco in fine sands. Soil Crop Sci. Soc. of
Florida Proc. 38:54-58.
9. SCS Engineering Division Stall. 1970. Irrigation Water Re
quirements. Technical Release 21, USDA. U. S. Government
Printing Office, Washington, D. C.
CORRECTION
The paper by T. L. Yuan, M. C. Lutrick, and W. K.
Robertson entitled Response of Soybeans and Oats to
Lime, Phosphorus, and Potassium on a Paleudult was
printed in error in the last issue of this Proceedings
(Soil and Crop Sci. Soc. Fla. Proc. 38: 116-121). Figures
3 and 4 are repetitions. Figure 4 should be as follows:
70 r
0 4.6 5.0 5.4 5.8 6.2 6.6 70 7.4
Soil pH
Fig. 4.Relationship between soil pH and oats yield in 1976.
Proceedings, Volume 39, 1980
3,


34
Soil and Crop Science Society of Florida
Soil-Water Characteristics of Histosols
as Related to Water Table Depth1
G. S. Rahi and S. F. Shih2
ABSTRACT
Soil water characteristics, imperative for designing
efficient water management systems, were studied in
subsiding organic soils (Histosols) in relation to dif
ferent water table depths. Soil samples were collected
at 5 to 15 and 15 to 30-crn depths from lysimeters where
water tables were maintained at 30, 60, and 90 cm
below the surface for about 3 years. A sugarcane
(Saccharum officinarum L.) crop was in its second
ratoon at the time of sampling. Results indicate that
water-yield coefficient values of the soil from the 60
and 90-crn water tables (WT) were 2 to 3 fold of those
obtained for soil from the 30-cm WT treatment. The
soil from the 15 to 30-cm depth in the 30-cm WT
treatment showed 5 to 10 times higher degree of re
sistance to initial wetting as compared with soil from
the 5 to 15-cm depth in the 30-cm WT and from the
5 to 30-cm depth in the 60 and 90-crn WT treatments.
The soil from the 15 to 30 cm depth in the 30-cm WT
combination also retained about 10 to 15% less water
at a given tension and released available water rela
tively faster than soil taken from other depths and
water table combinations at tensions higher than 4
bars. This layer of soil also appeared to possess 2 to 3
times lower saturated conductivity and capillary con
ductivity at a given degree of saturation as compared
with soil from the other sampling combinations.
Additional Index Words: Physical properties of
organic soils, Water yield coefficient, hydrophobic
nature of organic soils.
The study of soil water characteristics of organic
soil is very important for developing efficient water
management systems, especially in presence of high
water tables as recommended to reduce subsidence of
organic soils. High water tables not only require more
water for irrigation, but they also require more pump
ing for drainage after a heavy rainfall (Shih and
Gascho, 1980). However, the rate and amount of water
to be added or drained under specific conditions for
crop production largely depend on the water storage,
transmission, and release characteristics of the soil. All
of these properties are intimately related to the soil-
water characteristic of the soil.
A number of studies were reported in the literature
on the physical properties of organic soils in relation to
degree of humification and use of water-control sys
tems. Some of the related studies include those of
Boelter (1969, 1972) in Minnesota, Okruszko (1969)
in Poland, Korpijaakko and Radforth (1972) in Can
ada, Egglesmann (1972) in Germany, Pessi (1956) in
Finland, Clayton et al. (1942) and Weaver and Speir
(1960) in Florida, Boggie and Robertson (1972) in
^Florida Agricultural Experiment Station Journal Series No.
2314.
^Associate in Agricultural Engineering and Associate Professor
of Agricultural Engineering, respectively, University of Florida,
Agricultural Research and Education Center, Belle Glade, FL
33430.
Scotland, and Galvin (1972) in Ireland. Evaluation of
physical characteristics was also a significant com
ponent of many other studies conducted on muck soils
(Zelazny and Carlisle, 1974; Farnham and Finney,
1965; Feustel and Byers, 1930; and Hanrahan, 1954).
Most of these studies were conducted without any par
ticular relation to different water table depths. Lahde
(1972) studied seasonal variations in aerobic limits and
Pessi (1956) investigated thermal relations of organic
soils. Both of these studies were done in relation to
water table depths. The magnitude of subsidence and
microbial activity in relation to high water tables
were reported under subtropical conditions of south
Florida by many workers (Neller, 1944; Stephens, 1969;
Volk, 1972; and Tate, 1979). Unfortunately, not much
information is available on the concomitant physioco-
chemical changes induced by high water tables main
tained for long times. The main objective of this study
was to evaluate any variations induced by high water
table that might lie of consequence in designing ade
quate water management systems on organic soils.
MATERIALS AND METHODS
These studies were conducted under simulated
conditions in 1.2 m deep and 5.5 m diameter lysimeters.
Water table depths in these lysimeters were controlled
at 30, 60, and 90 cm below the soil surface in duplicate.
Organic soil was packed in the lysimeters to the bulk
density closely representing field conditions. Lysimeters
were installed 3 years prior to this study by Gascho and
Shih (1979) to evaluate the performance of sugarcane
(Saccharum officinarum L.) in relation to different
water table depths. A crop of sugarcane was in its
second ratoon when the soil samples were taken. Dis
turbed and undisturbed soil samples were taken from
5 to 15 and 15 to 30-cm depths in each lysimeter. Dif
ferent physical parameters monitored are described
below:
1. Water-Yield Coefficient: This coefficient meas
ured the amount of water released as the water table
receded in the soil. Undisturbed soil cores were taken
at two depths from four locations in each lysimeter.
The saturated core samples were subjected to 0.10 bar
pressure. Amount of water released between saturation
and 0.10 bar tension was used to represent the water-
yield coefficient (Boelter, 1969).
2. Rubbed and Unrubbed Fiber Percentage: These
percentages were used to indicate the degree of humifi
cation of peat. Undisturbed samples in cores were col
lected at two depths and four locations in each
lysimeter. Two samples from each depth were used to
determine the total oven dry mass (105 C). The other
two samples were analyzed for three main particle size
fractions, i.e., particles > 1 mm, in between 1 and 0.1
mm, and particles <0.1 mm in diameter according to
the method developed by Farnham and Finney (1965).
3. Water Drop Penetration Time Test: This test
was used to measure indirectly the degree of resistance
to wetting. The test actually measured the degree of
stability of hydrophobic nature of the soil.


35
Proceedings, Volume 39, 1980
This test and other subsequent physical property
determinations were conducted on disturbed soil sam
ples. Disturbed soil samples were taken to avoid any
interference from the roots and other extraneous
matter in evaluating the physical properties of organic
soil particles. Soil samples were collected from four
locations at two depths in each lysimeter. Soil was air
dried and passed through a 2-mm sieve.
Smooth surfaces were prepared in triplicate from
each sample and a medicine chopper was used to get a
uniform size water drop. The amount of time each
drop took to disappear was noted.
4. Saturated Hydraulic Conductivity: Saturated
conductivity was determined by packing air-dry soil to
the same bulk density in three layers in brass cores.
Measurements were made in triplicate by the standard
technique with constant water head (Klute, 1965).
5. Soil Water Retention and Release Relations: Soil
samples from each location were compacted to the same
density in small cores. The saturated samples were
subjected to tensions ranging from 1/3 to 15 bars in
the pressure chamber apparatus. Retention and release
of volumetric water content were studied as functions
of tension.
6. Available Water: Available range of water was
computed from the difference in the amounts of volu
metric water content retained at 1/3 bar and 15 bars.
This availability range was included to be studied as a
function of tension to see how the soil texture affected
water release in relation to degree of unsaturation at
a given density as far as availability of water to plants
was concerned.
7. Capillary Conductivity: Unsaturatecl hydraulic
conductivity was computed theoretically from the satu
rated hydraulic conductivity and soil water tension re
lations using the mathematical relationships of Camp
bell (1974). Capillary conductivity was determined to
study the empirical relation of decrease in hydraulic
conductivity on a relative basis with degrees of satura
tion over the available water range in the organic soils.
RESULTS AND DISCUSSION
Results obtained from various physical properties
were interpreted to establish any trend of change in
soil-water characteristics of organic soils in relation to
different water table depths. These studies were con
fined to the surface 30-cnr depth mainly for the reason
that predominant microbial activity was found to be
confined to the top few cm of soil (Tate, 1979). There
fore, any changes in the physical properties of the
medium were probably better reflected in the surface
soil as affected by its closeness to water table depth.
Data on water-yield coefficients are given in Table
1. These values, which vary on the average from 0.11 to
0.38 cm3/cm3, indicate that a larger volume of water
was released with receding water-table in the 90-cm
water table than any other water-table combination at
any depth. The least amount of water was released at
15 to 30-cm depth in the 30-cm water table treatment.
These water-yield coefficients were in the range of those
reported by Boelter (1974) for the moderately de
composed to well decomposed peat in Minnesota. One
probable reason for the lower water-yield coefficient in
the 30-cm water table depth was the lower amount of
water retained at both saturation and 1/10 bar tension,
TABLE 1.Water yield coefficients as related to water table
DEPTH.
Water table
depth
(cm)
Depth of
sampling
(cm)
Water yield coeff.
(cm31 cm3)
Rep I
Rep II
Avg.
90
5-15
.40
.36
.38
15-30
.34
.38
.34
60
5-15
.35
.29
.32
15-30
.24
.25
.24
30
5-15
.15
.16
.16
15-30
.14
.08
.11
which was due to an overall lower total porosity ob
served in this soil.
Proportions of rubbed and unrubbed fiber are
given in Table 2. Since the differences in the average
of determined values of various physical properties for
5 to 15 cm and 15 to 30-cm depths were small for the
60 and 90-cm water table depths, these values were
combined and their averages were used for making
interpretations. The values given in Table 2 in general
indicate that the proportion of rubbed and unrubbed
fibers for the 60-cm water table depth was quite close
to the proportion for the 90-cm depth. These values
were about 44 and 56%, respectively. However, two
replication averages did not give consistent results for
the 30-cm water table treatment, especially at the 15
to 30 cm sampling depth. The presence of secondary
and tertiary roots of sugarcane grown for the third
generation could be partly responsible for these in
consistencies in the soil layers above high water table.
Water drop penetration time results are given in
Table 3. These results indicate that the soil from the
15 to 30-cm depth of the 30-cm water table treatment
was the most resistant to wetting followed by the soil
zone above this hydrophobic layer. Degree of hy
drophobic nature of soil from the 90 and 60-cm water
table combinations were next in that order. However,
the problem was initial wetting; as the soil became wet
it behaved as other soil samples. Bond and Harris
(1964) observed that water repellency in soil was caused
by metabolic products of microorganisms. Though no
specific efforts were made to measure degree of swelling
on wetting, visual observations indicated that soil from
deep water table combinations swelled noticeably much
more than soil taken from a shallow water-table depth.
TABLE 2.Rubbed and unrubbed fiber analysis for different
WATER TABLE DEPTHS.
Water
table
depth
(cm)
Sampling
depth
(cm)
Rep
Prop, particle size frac.
(%)
> 1 mm
0.1-1 mm
0.1 mm
5-30
I
27.37
32.61
40.02
90
II
29.68
28.05
42.27
Avg
28.53
30.33
41.14
5-30
I
27.80
28.59
43.61
GO
II
24.93
31.76
44.31
Avg
26.06
30.18
43.96
5-15
I
17.31
31.11
51.58
30
II
20.52
33.63
45.85
Avg
18.92
32.37
48.72
15-30
I
23.22
42.76
34.02
30
II
17.30
31.80
50.90
Avg
20.26
37.28
42.46


36
Soil and Crop Science Society of Florida
Soil samples taken from the 15 to 30-cm depth in the
30-cm water-table depth plots did not show any
swelling effect. Disturbed soil samples gave empirical
relations without much reflection on the structural
arrangement of soil particles. However, these studies
did indicate the changes in the physical nature of
organic soil particles induced by water table depth.
Data on saturated hydraulic conductivity are also
given in Table 3. The data indicate that the conduc
tivity was maximum in the 90-cm water table depth
followed by the 60-cm water table. The saturated con
ductivity was the least in samples collected from 15
to 30-cm depth in the 30-cm water table treatment. The
lower conductivity in these shallow water table soil
samples could be due to smaller size of particles as is
also indicated by data given in Table 2. The decreased
conductivity of the soil layer above the shallow water
table (30-cm water table depth) could be due to a
gradual disappearance of hydrophobic character of soil
particles which then could have dispersed and clogged
the soil pores. These conductivity values were higher
by 10 fold than those reported by Weaver and Speir
(1960), Zelazny and Carlisle (1974), and Snyder et al.
(1978). The high values were obtained probably be
cause the disturbed soil samples were used and they
were not well packed.
Retention of volumetric water content at different
tensions between 1/3 and 15 bars is plotted in Fig. 1.
The general shape of the curves for all the soils and
the computed mathematical equations appear to be
similar to the typical soil water tension relations re
ported by Hillel (1971). Soil samples taken from the
60-cm water-table treatment retained more water than
samples taken from 90 and 30-cm water-table plots at
a given tension. However, there was not much differ
ence in amount of water retained in soil samples col
lected from different water table depth combinations
except in soil samples collected from 15 to 30 cm in
the 30-cm water table treatment at a given suction. Soil
from the zone above the shallow water table retained
about 0.05 to 0.10 cm3/cm3 less water at a given degree
of unsaturation over the available water range.
Percent available water was plotted as a function of
tension and is given in Fig. 2. The available volumetric
water content varied between 0.17 to 0.18 cm3/cm3 for
the 90 and 60-cm water-table treatments at 5 to 30-cm
depth and 30-cm water table treatment at 5 to 15-cm
depth. But, for the 30-cm water table treatment at 15
TABLE 3.Water drop penetration time test and hydraulic
CONDUCTIVITY VALUES FOR SOIL IN RELATION TO WATER TABLE DEPTH.
Water
table
depth
(cm)
Sampling
depth
(cm)
Rep
Water drop
penetration
time (sec)
Sat.
conductivity
cm/min
I
7.2
9.86
90
5-30
II
7.8
7.81
Avg
7.5
8.83
I
3.0
7.72
60
5-30
II
4.8
6.12
Avg
3.9
6.92
I
9.0
4.70
30
5-15
II
9.6
6.13
Avg
9.3
5.41
I
48.0
2.97
30
15-30
II
30.0
3.65
Avg
39.0
3.31
Fig. 1.Soil water tension relations as affected by water table
depth.
Fig. 2.Percent available water versus tension relations for
soil from different water table lysimeters.
to 30-cm depth this value was only 0.14 cm3/cm3. The
relationship in Fig. 2 indicates that there was no sig
nificant difference in the release of available water in
all combinations before 1-bar suction was approached.
About 35 to 40% of the available water was released as
the soil drained to 1 bar suction. At a suction of 8 bars
nearly 78 to 83% of available water was released in all
combinations except in soil from the 15 to 30-cm depth
of the 30-cm water table plots where as much as 94%
of available water was depleted. This indicated a rela
tive decrease in the physical activity of soil particles
caused by a decrease in surface adsorption forces. In
the wet range, it is the arrangement and particle size
that play a dominant role in soil water retention and
release whereas in the dry range water retention is
more a function of the soil particles surface properties.
Computed capillary conductivity values were plot
ted as a function of volumetric water content (Fig. 3).
The values in general indicate that capillary conduc
tivity decreased about 10 fold from saturation to field
capacity. Hydraulic conductivity could decrease from
100 to 1,000 times in this range for many soils as was
reported by Hillel (1971). The capillary conductivity
in the water content range of 0.45 and 0.20 cm3/cm3
decreased only 5 to 8 fold for all combinations except,
again, in the soil layer lying immediately above the
shallow water-table. The decrease in conductivity in


37
Proceedings, Volume 39, 1980
Fig. 3. Calculated capillary conductivity versus volumetric
water content relations.
this soil layer was only 3 fold. These water content
values corresponded to field capacity and 8-bar suc
tion, respectively. The unsaturated conductivity values
appeared to be quite high as compared with most soils.
From the results of these studies it can be concluded
that the three factors responsible for water release and
water retention in soils (i.e., the soil particle size, ar
rangement, and physicochemical nature which control
surface adsorption forces) were affected in organic soils
by the water table. This was indicated by the changes
observed in the physical constituents of the soil layer
above the shallow water table. A decrease in total
porosity, hydraulic conductivity, and physical water
adsorption activity, and an increase in hydrophobic
nature signified the presence of a soil zone that had less
capacity to hold an additional amount of water not
only because of its nearness to the water table but also
because of physical changes induced in the internal
make up of the soil. This could produce more run
off and more erosion and should be given due con
sideration in designing efficient water-management
systems on organic soils of the area. This means that a
water-management system designed to maintain a high
water table in organic soils should have adequate
drainage capability. This is important especially dur
ing a wet season to protect crop roots from standing
water for a long period of time.
LITERATURE CITED
1. Boelter, D. H. 1969. Physical properties of peats as related
to degree of decomposition. Soil Sci. Soc. Am. Proc. 33:606-
609.
2. Boelter, D. H. 1972. Preliminary results of water level control
on small plots in a peat bog. 4th Int. Peat Congr. (Otaniemi,
Finland) Proc. 3:347-354.
3. Boelter, D. H. 1974. The hydrologic characteristics of un
drained organic soils in the Lake States. In A. R. Aandahl,
S. W. Buol, D. E. Hall, and H. H. Bailey (ed.) Histosols
Their characteristics, classification, and use. SSSA Special
Pub. No. 6. Soil Sci. Soc. Am., Inc., Madison, Wis.
4. Boggie, R., and R. A. Robertson. 1972. Evaluation of horti
cultural peat in Britain. 4th Int. Peat Congr. (Otaniemi,
Finland) Proc. 3:185-192.
5. Bond, R. D., and J. R. Harris. 1964. The influence of micro-
flora on physical properties of soils. I. Effects associated with
filamentous algae and fungi. Aust. J. Soil Res. 2:111-122.
6. Campbell, G. S. 1974. A simple method for determining un
saturated conductivity from moisture retention data. Soil
Sci. 117:311-314.
7. Clayton, B. S., J. R. Neller, and R. V. Allison. 1942. Water
Control in the peat and muck soils of Florida Everglades.
Florida Agr. Exp. Sta. Bull. 378.
8. Egglesmann, R. 1972. The thermal constants of different
highbogs and sandy soils. 4th Int. Peat Congr. (Otaniemi,
Finland) Proc. 3:371-382.
9. Farnham, R. S., and H. R. Finney. 1965. Classification and
properties of organic soils. Adv. Agron. 17:115-162.
10. Feustel, I. C., and H. G. Byers. 1930. The physical and chem
ical characteristics of certain American peat profiles. USDA
Tech. Bull. 214.
11. Galvin, L. F. 1972. Reclamation of Irish peats for agricultural
development. 4th Int. Peat Congr. (Otaniemi, Finland) Proc.
3:425-434.
12. Gascho, G. J., and S. F. Shih. 1979. Varietal response of sugar
cane to water table depth, I. Lysimeter performance and
plant response. Soil and Crop Sci. Soc. of Florida Proc. 38:
23-27.
13. Hanrahan, E. T. 1954. An investigation of some physical
properties of peat. Geotech. 4:108-123.
14. Hillel, D. 1971. Soil and water,Physical Principles and
Process. Academic Press, New York.
15. Klute, A. 1965. Laboratory measurement of hydraulic con
ductivity of saturated soil. In C. A. Black (ed.) Methods of
Soil Analysis (Part I). Agronomy 9:253-261. Am. Soc. of
Agron., Madison, Wis.
16. Korpijaakko, M., and N. W. Radforth. 1972. Studies on
the hydraulic conductivity of peat. 4th Int. Peat Congr.
(Otaniemi, Finland) Proc. 3:323-334.
17. Lahde, E. 1972. Seasonal variations in the depth of aerobic
limit and the ground water table in virgin and in drained
Myrtillus spruce swamp. 4th Int. Peat Congr. (Otaniemi,
Finland) Proc. 3:355-370.
18. Neller, J. R. 1944. Oxidation loss of low moor peat in fields
with different water tables. Soil Sci. 58:195-204.
19. Okruszko, H. 1969. Muck soils of valley peat bogs and their
chemical and physical properties. Translated from Polish by
USDA, Roczn. Nauk. Roln. 74:5-89.
20. Pessi, Y. 1956. Studies on the effect of the admixture of
mineral soil upon the thermal conditions of cultivated peat
land. State. Agr. Res. Pub. of Finland No. 147, Helsinki,
Finland.
21. Shih, S. F., and G. J. Gascho. 1980. Water requirements for
sugarcane production. Transactions of the Am. Soc. of Agre.
Eng. (in press)
22. Snyder, G. H S. F. Shih, and D. L. Myhre. 1977. Character
istics of inplace and potential soil fill materials as related to
water leaching at the surfside landfill in Dade County. Final
Report on Town of Surfside Landfill Closing Study, Airan
Environmental Consultants, Inc., Coral Gables, Fla.
23. Stephens, J. C. 1969. Peat and muck drainage problems. J. of
Irrig. and Drainage Division. Am. Soc. Civil Eng. 95(IR2):
285-305.
24. Tate, R. L. 1979. Microbial activity in organic soils affected
by soil depth and crop. Applied and Environ. Microbiol. 37:
1085-1090.
25. Volk, B. G. 1972. Everglades histosol subsidence. I. C02
evolution as affected by soil type, temperature, and moisture.
Soil Crop Sci. Soc. Florida Proc. 32:132-135.
26. Weaver, H. A., and W. H. Speir. 1960. Applying basic soil
water data to water control problems in Everglades peaty
muck. USDA. ARS Bull. 40-41.
27. Zelazny, L. W., and V. W. Carlisle. 1974. Physical, chemical,
elemental, and oxygen-containing functional group analysis
of selected Florida Histosols. In A. R. Aandahl et al. (ed.)
Histosols. Their characteristics, classification, and use. SSSA
Special Pub. No. 6. Soil Sci. Soc. of America, Inc., Madison,
Wis.


38
Soil and Crop Science Society of Florida
Major Land Resource Areas in Florida
R. E. Caldwell1
ABSTRACT
Three categories of land resource maps used in the
United States are introduced and briefly defined. They
are land resource regions, major land resource areas,
and land resource units. Greater emphasis is given to
major land resource areas (MLRAs) as they comprise
the groupings being considered for a new general soil
map of Florida presently in preparation. Two earlier
MLRA maps by the USDA Soil Conservation Service,
one in 1973 and the other in 1978, are presented and
discussed as to their suitabilities. Finally, a revised
MLRA map is proposed for consideration as constitut
ing the Major Land Resource Areas of Florida upon
which the new general soil map of the State should be
based.
Additional Index Words: Land resource maps,
MLRAs, General soil map of Florida, Soil taxonomy,
Soil survey.
It is often quite important to assemble and organize
currently available information concerning land as a
resource for a wide variety of uses, including agricul
tural, industrial, recreational, engineering, and others.
Such information can best be presented in the form of
a map and a report, either of which can be revised as
improved technology provides new information.
In the preparation of land resource maps at nat
ional and state levels, three categories have evolved:
(a) land resource regions, (b) major land resource
areas, and (c) land resource units (1). Land resource
regions consist of geographically associated major land
resource areas and are most significant for land-use
planning on a national scale. Major land resource
areas are defined as consisting of geographically asso
ciated land resource units and are most important in
land-use planning on a state-wide level, although such
areas also have value in inter-state, regional, and
national planning. Land resource units consist of
geographic areas of land that are characterized by
particular patterns of soil and climate. A unit may
occur as a single continuous area or as several separate
but nearby areas which usually comprise several
thousand acres in extent. Many such units are also
known as soil associations. It is readily apparent, there
fore, that uniformity is greatest in land resource units,
considerably less in major land resource areas, and very
much less in land resource regions. It is also clear that
somewhat similar units may be grouped into a single
area, and similar areas (in turn) are often grouped to
gether within a single region.
This paper is primarily concerned with the dis
tribution and extent of various major land resource
areas (MLRAs) in Florida as designated in the past
and also with suggested changes which more ade
quately describe each of the MLRAs and show their
extent and distribution within the State.
iProfessor (Genesis and Classification), Soil Science Depart
ment, Florida Agricultural Experiment Station, Gainesville, FL
32611.
HISTORY
A general soil map of Florida (5) was published in
1962 which grouped dominant soils into associations
based primarily on drainage and kind of parent ma
terials from which they were developed. A bulletin was
later published as a supplement to this map which
described each of the mapping units (4).
With increased knowledge in regard to soil genesis,
morphology, and classification, a new system of soil
classification was adopted for use in the United States
on 1 January 1965. The development of this classifica
tion scheme began in 1951 and underwent a series of
revisions or approximations before it was finally pub
lished as Soil Taxonomy (6) in 1975. This new system
treats soil as individual three-dimensional entities
which can be grouped together according to their
physical, chemical, and mineralogical characteristics
(2). Soil taxonomy now requires improved soil profile
descriptions to greater depths in the field supple
mented with specialized laboratory data. This has re
sulted in more precise definitions of most older soil
series and recognition of many new series. For example,
some of the soils in the earlier concept of the Lakeland
soil are now included in 11 other soil series, several of
which are completely new.
It is, therefore, necessary that a revised general soil
map of Florida be published based on present soil
taxonomy, especially since the previous map and report
on Florida soils are out-of-date and out-of-print. Prog
ress is being made toward this project by personnel of
the Florida Agricultural Experiment Stations in co
operation with the USDA Soil Conservation Service.
MLRA MAPS OF FLORIDA
During the early planning of this revised general
soil map, it was decided to group the various soil asso
ciations into MLRAs (each of which would be dis
tinguished from one another on the State map by its
own color) for ease of presentation and understanding.
Accordingly, a study was made of various MLRA
maps of the State of Florida.
One of these (Fig. 1) by the USDA-SCS in 1973 is
a slightly revised version of a small MLRA map shown
in the upper right-hand corner of the previous general
soil map of Florida (5). While the Southern Coastal
Plain and the Atlantic Coast Flatwoods properly
match up with the adjoining MLRAs in Alabama and
Georgia, several other judgments make this map un
suitable. These are: (a) the South Central Florida
Riclge extends too far to the north (almost as far as
the North-Central Florida Ridge), (b) the Southern
Florida Flatwoods extend up into Duval County
which is certainly not part of South Florida, (c) the
Atlantic Coast Flatwoods end in Duval County, but
the Atlantic Coast certainly extends all the way down
the eastern coast of Florida, and (d) the Gulf Coast
Flatwoods end near the southern Pasco County
border, but the Gulf Coast definitely extends much
farther south along the western coast of the State.
Perhaps recognizing that changes can be made in
MLRA boundaries, the Soil Conservation Service


Proceedings, Volume 39, 1980
39
HU Southern Coastal Plain
f 1 North-Central Florida Ridge
- South-Central Florida Ridge
_ Atlantic Coast Flatwoods
- Eastern Gulf Coast Flatwoods
Southern Florida Flatvjoods
Southern Florida Lowlands
Florida Everglades & Associated Areas
Fig. 1.Major land resource areas (SCS 1973).
(SCS) shows these revisions as occurring in the State
as of September 1978 (Fig. 2). Here again, the South
ern Coastal Plain and the Atlantic Coast Flatwoods
match up well with the MLRAs in Alabama and
Georgia, but other faults and misnomers still exist to
make this MLRA map unsuitable. They are: (a)
the South-Central Florida Ridge extends up into
Alachua and Clay Counties, which are certainly not
considered to be part of South Florida, (b) the South
ern Florida Flatwoods still extend up into Duval
County with a small area shown in Alachua County,
both of which are much too far north of areas con
sidered to be Southern Florida, (c) the Atlantic
Coast Flatwoods still end in Duval County, but the
Atlantic Coast certainly extends all the way down the
eastern coast of Florida and, (cl) the Gulf Coast Flat-
woods end at the southern boundary of Levy County,
but the Gulf Coast definitely has flatwood areas farther
south along the western coast of the State.
If MLRAs are indeed to be the broad groupings
upon which the new general soil map of Florida is to
be based, it is evident that still more revisions in their
boundaries and nomenclature are needed in order to
overcome the objections detailed above. The map
shown in Fig. 3 was prepared from land area informa
tion contained in the Florida General Soils Atlas (3),
and the names of MLRAs were also changed to better
describe the areas involved.
A study of this MLRA map of Florida reveals those
changes made to include the following: (a) the South
ern Coastal Plain and the Atlantic Coast Flatwood
still match-up with the MLRAs in Alabama and
Georgia; however, some changes have been incorpo
rated in their southern in-State boundaries due to im
proved current knowledge, (b) the Central Florida
Ridge includes those areas formerly listed as North-
Central and South-Central Florida Ridge, with
relatively minor changes in boundaries, (c) the South
ern Florida Flatwoods has its northern boundary
moved southward from Duval County to the areas
including Orange and Brevard Counties, (d) the
Atlantic Coast Flatwoods and the Gulf Coast Flat-
Fig. 2.Major land resource areas (SCS 1978).
Fig. 3.Major land resource areas (Proposed).
woods now extend along the Atlantic and Gulf
coasts, respectively, in a southerly direction until they
border a different MLRA, and (e) the Everglades and
Associated Areas are connected (thus differing from
Fig. 1 and also include the Southern Florida Low
land shown in Fig. 2).
It is proposed that this map (Fig. 3) be accepted
by state and federal agencies, with perhaps only
slight modifications if necessary, as the Major Land
Resource Areas of Florida. To permit the use of
these MLRA designations on the general soil map to
be published at a scale of 1:1,000,000, an additional
map unit entitled Miscellaneous Land Types would
most probably be needed. It would include such areas
as coastal beaches and dunes, saltwater marshes and
swamps, and certain alluvial lands bordering the larger
rivers such as the Escambia, Apalachicola, and


40
Soil and Crop Science Society of Florida
Ochlockonee. Due to the scale of the maps in this
paper, this last proposed MLRA could not be shown.
LITERATURE CITED
1. Austin, M. E. 1965. Land resource regions and major land
resource areas. USDA Handbook No. 296. Washington, D.C.
82 p.
2. Caldwell, R. E. 1978. Soil taxonomy; a new improved system
of soil classification, p. 22-33. In Soil Identification Handbook.
Univ. Florida Soil Science Publ., Gainesville, Fla.
3. Florida Division of State Planning. 1974. The Florida general
soil atlas: with interpretations for regional planning districts
I through X, (set of 5). State of Florida, Tallahassee, Fla.
4. Smith, F. B., R. G. Leighty, R. E. Caldwell, V. W. Carlisle,
L. G. Thompson, Jr., and T. C. Mathews. 1967. Principal soil
areas of Florida, a supplement to the general soil map. Univ.
Florida Agrie. Exp. Sin. Bui. 717. Gainesville, Fla.
5. Soil Survey Staff. 1962. General soil map of Florida. Univ.
Florida Agrie. Exp. Stn. Publ. in coop. USDA Soil Consen'.
Serv., Gainesville, Fla.
6. Soil Survey Staff. 1975. Soil taxonomy; a basic system of soil
classification for making and interpreting soil surveys. USDA-
SCS Agrie. Handbook No. 436. U.S. Government Printing
Office, Washington, D.C.
Sulfur Fertilization of Com Seedlings1
C. C. Mitchell, Jr. and R. N. Gallaher2
ABSTRACT
Lack of sulfur (S) in many fertilizer materials used
on crops under intensive multiple cropping may cause
plant nutrient imbalances that reduce yield. The
purpose of this experiment was to determine the need
for S on two cultivars of corn (Zea mays L.), to evalu
ate different sources of S, and to determine the most
effective method of application of S to corn seedlings.
A N:S imbalance was observed in emerging corn seed
lings in the spring of 1979. This imbalance may have
been caused by high fertilizer rates and intensive man
agement with no S applied to a multiple-cropping,
minimum-tillage experiment on an Arredondo fine
sand (loamy, silicious, hyperthermic Grossarenic
Paleudult) in north-central Florida. Two rates of foliar-
applied magnesium sulfate and potassium sulfate (5
and 10 kg/ha S) and one rate of agricultural-grade
magnesium sulfate, potassium sulfate, and calcium sul
fate (10 kg/ha S) were applied to 30-day-old plants of
a short-season corn grain variety and a full-season corn
forage variety.
All of the S treatments increased the S concentra
tion in mature leaves of 55-day-old plants and in the
total plant of the full-season forage variety at harvest.
However, neither grain nor forage yield or quality was
influenced by the S treatments. All plants had grown
out of the S-deficient condition at 55 days. They were
marginally Mg deficient 21 days after emergence. As
the plants grew out of the S deficiency, Mg became the
most limiting nutrient. The short-season variety gave
a positive yield response to Mg in both the foliar spray
and in the agricultural-grade material. The full-season
variety did not respond to the Mg treatments but
yielded 37 % more grain than the short-season variety.
Additional Index Words: Mg response on corn,
Multicropping fertilization.
The sandy soils of north Florida are low in avail
able sulfur (S). Neller (1959) found that the extract-
iFlorida Agricultural Experiment Stations Tournal Series Num
ber 2220.
^Graduate Assistant, Soil Science Department, and Associate
Professor of Agronomy, Agronomy Department, Institute of
Food and Agricultural Sciences, University of Florida, Gaines
ville, FL 32611.
able sulfate-S concentration of the surface horizons of
some Florida soils ranged from 0 to 4.5 ppm, and clover
responded to applications of S in all areas of the state
(Neller et ah, 1951; Neller, 1952). Deep-rooted plants
are able to utilize adsorbed sulfate associated with the
clay in lower soil horizons, but seedlings may exhibit
S-deficiency symptoms when grown on sandy surface
soils with no S fertilization (Neller, 1959; Ensminger,
1954). With intensive management, S-free fertilizers,
and little S available to crops through the atmosphere,
rainfall, or irrigation, S deficiencies are likely to be
come more widespread for crops grown on Florida soils.
Interest in multiple cropping and minimum tillage
as intensive management practices is increasing
throughout Florida. Multicropping practices require
careful soil fertility management since the several crops
removed in a season require more nutrients than the
single crop ordinarily planted. Corn planted in 1979
in an established, multiple cropping, minimum tillage
experiment emerged with symptoms of S deficiency.
Several commercial corn crops in north-central Florida
were also observed witli symptoms indicating S and/or
Mg deficiencies early in the season. The objective of
the study reported here was to evaluate different
S-containing chemicals as fertilizers for correcting the
S deficiency symptoms observed in the seedling corn.
MATERIALS AND METHODS
In 1977, a multiple cropping, minimum tillage ex
periment was begun at the Green Acres Agronomy
Farm in north-central Florida on an Arredondo fine
sand (loamy, silicious, hyperthermic Grossarenic
Paleudult). One phase of this experiment involved the
following cropping system.
1. Wheat (Triticum aestivum L. Holley) was
planted in late fall and harvested as forage in
early spring.
2. Two corn (Zea mays L.) hybrids were planted in
early spring in the wheat stubble, (a) The short-
season hybrid (Dekalb XL-12) was harvested in
mid-summer for grain (corn grain system), (b)
The full-season hybrid (Dekalb XL-395A) was
harvested for forage at the same time (corn
forage system).
3. Forage sorghum (Sorghum bicolor L. Dekalb
FS24), millet (Pennisetum americanum L.


41
Proceedings, Volume 39, 1980
Gahi 3) or a sorghum x sudangrass hybrid
(Sorghum sudanense (Piper) Stapf Dekalb
SX16) was planted after the corn and harvested
for forage in the fall.
From the spring of 1977 to the spring of 1979, seven
crops were grown and harvested on the experimental
site. High rates of N, P, and K and clolomitic limestone
were applied to produce the crops, but no S was ap
plied.
In the spring of 1979, corn seedlings of both the
short-season (85-90 day) grain variety and the full-
season (120-125 day) forage variety emerged with
S-deficiency symptoms. Analysis of samples of the 21-
clay-old seedlings verified the symptoms as a N:S im
balance.
The corn plots of the multicropping experiment
were subdivided into a split-plot experiment with two
corn varieties as the main plots. Eight S treatments
were applied as either foliar sprays or agricultural-
grade material (Table 1). Treatments were replicated
five times. The foliar sprays were applied in two ap
plications, 10 days apart, beginning when the plants
were 30 days old. All of the agricultural grade ma
terials were applied when the plants were 30 days old.
Leaf samples were taken from the uppermost, ma
ture leaves 14 days after the final foliar fertilization
(pretassel stage for Dekalb XL 12). Leaf samples were
dried at 70 C in a forced-air oven, ground to pass a
1-mm screen, ashed, and analyzed for P, K, Ca, Mg, Zn,
Cu, and Mn. Nitrogen was determined by an auto
mated procedure with a Technicon AutoAnalyzer. A
100-mg sample of the dry, ground tissue was placed
into a 75-ml pyrex test tube. These samples were di
gested in a mixture of 10 ml concentrated H,S04, 2 ml
of H202, and 3.2 g of a salt-catalyst mixture (90%
KS04: 10% CuS04) with three boiling chips for 2.5
hours on an aluminum block heated to 385 C. The
digested liquid was then diluted to 75 ml with distilled
water and analyzed for N. Sulfur was measured by a
turbidometric method after pre-digestion with a Mg
TABLE 1.Sources, rates, and methods of application of S.
Source
S ratef
Method
-kg/ha-
Magnesium sulfate
(MgS04.7H20)
5
Foliar spray
Magnesium sulfate
(MgS04.7H20)
10
n n
Potassium sulfate
(K2so4)
5
n //
Potassium sulfate
(k2so4)
10
n n
Magnesium sulfate
(Agricultural grade)
10
Soil applied
Potassium sulfate
(Agricultural grade)
10
// n
Calcium sulfate
(Agricultural grade)
10
// n
Check
0

fFoliar sprays were applied to 30-day old seedlings in two
applications, 10 days apart. Agricultural grade material was ap
plied to soil in one application.
(N03)2/HN03 solution and ashing in a muffle furnace
(Massoumi and Cornfield, 1963; Chaudry and Corn
field, 1966). The residue was dissolved in 0.1N HC1.
For analyses of the other nutrients, 1 g of plant tissue
was ashed in a muffle furnace, dissolved in 0.1N HC1
and brought to 100 ml volume. Phosphorus concentra
tion was measured with a Technicon Auto-Analyzer.
Potassium was determined by flame emission, and the
other cations were determined by atomic absorption
spectrophotometry.
Dekalb XL-12 was harvested for grain 122 days after
planting. At the same time, Dekalb XL-395A was har
vested for forage by removing the above-ground por
tion of the plant. Whole-plant samples were taken from
the forage corn. Grain samples were taken from both
varieties.
The soil was sampled from an area adjacent to the
experiment. Samples were collected from four depths,
0 to 15 cm, 15 to 30 cm, 30 to 60 cm, and 60 to 80 cm.
Samples were screened and air dried. Extractable
S04-S was determined by extracting the soil with a
0.01A4 Ca(H2PO,)2. H20 solution and determining S
turbidometrically (Ensminger, 1954; Fox et ah, 1964).
RESULTS
Analyses of the 21-day-old seedlings are reported in
Table 2. These plants were definitely low in S with an
average S concentration of 0.12%. The critical con
centration of S in young corn plants has been reported
to be around 0.20% (Fox et ah, 1964; Stewart and
Porter, 1969; Jones and Eck, 1973; Terman et al.,
1973). The N:S ratios of 39 and 42 for the two cultivars
were larger than the optimum of 16 for plant protein
(Terman et ah, 1973). The seven harvested crops in the
corn grain system and the corn forage system removed
an estimated 48 and 63 kg/ha S, respectively, during
the two previous years (Table 3). No fertilizer S was
applied during this time. Removal of N,P,K, and Mg
in the harvested portion of the crop was calculated to
be in balance with that applied.
Applied S from non-Mg sources had no significant
effect on the final grain yield of either variety of corn
(Table 4). The full-season variety (Dekalb XL395A)
yielded 37% more than the short-season variety. This
may be attributed to the fact that the long-season corn
had a longer growing period in which to recover from
the initial stunting due to the severe S deficiency. The
short-season variety never fully recovered and prob
ably was unable to develop an extensive root system
before flowering.
TABLE 2.Mineral concentration of 21-day-old corn seed-
LINGS.f
N
S
P
K
Ca
Mg
N/S
%
Dekalb XL12
(grain)
4.62
0.117
0.83
3.39
0.42
0.19
39
Dekalb XL39SA
(forage)
5.04
0.121
0.87
3.15
0.39
0.20
42
Critical
levelsj
3.5
0.20
0.40
3.0
0.20
0.20
16
f All values are the means of five replications.
JFox et al., 1964; Stewart and Porter, 1969; Jones and Eck.
1973; Terman et al., 1973.


42
Soil and Crop Science Society of Florida
TABLE 3.Nutrients applied and removed from the soil by two cropping systems over a 2-year
PERIOD.
Crop
Dry
Nutrients applied matter
Year N P K Mgt harvested
Nutrients removed
P K Mg SJ
kg/ha
Corn grain system
Wheat forage
1977
111
18
84
385
2,985
63
11
58
4
3
Corn grain
//
188
34
297
0
3,620
66
14
14
4
4
Summer forage
rr
113
0
0
0
7,530
105
22
177
20
15
Wheat forage
Corn grain
1978
111
18
84
0
2,504
59
10
63
4
3
rr
188
34
297
0
5,870
86
19
29
6
6
Summer forage
rr
113
0
0
0
6,844
79
16
151
17
14
Wheat forage
1979
111
18
84
0
3,124
91
13
60
4
3
TOTAL
935
122
846
385
32,474
Corn forage system
549
105
552
59
48
Wheat forage
1977
111
18
84
385
2,930
63
11
61
3
3
Corn forage
tt
188
34
297
0
23,940
268
53
306
36
19
Summer forage
//
113
0
0
0
6,269
122
19
137
19
13
Wheat forage
1978
111
18
84
0
2,334
57
12
67
4
2
Corn forage
//
188
34
297
0
12,940
131
27
107
21
10
Summer forage
rr
113
0
0
0
6,255
72
16
126
17
13
Wheat forage
1979
111
18
84
0
3,048
86
12
66
4
3
TOTAL
935
122
846
385
57,716
799
150
870
104
63
fMg from 4.5 metric tons/ha of dolomitic limestone containing 30% MgCOs.
fS removal estimated from tissue analyses from 1979 samples and from values reported in the literature.
TABLE 4.Leaf and grain analyses and yields of two corn cultivars as affected by rates of
FOLIAR APPLIED S.
s
rate
Leaf analysis at 55 days
Mg:cation
S* N Mg Ca ratio
Grain analysis at harvest
Mgrcation Yield
S N Mg Ca ratio Grain Forage
% %
Dekalb XL-12 (short-season)
0
0.17c*
2.67
0.10
0.25
0.11
0.11
1.65
0.12
.004
0.49
5
0.21b
2.50
0.12
0.23
0.12
0.11
1.71
0.12
.002
0.48
10
0.25a
2.48
0.12
0.23
0.12
0.10
1.74
0.12
.003
0.48
quintal/ha
26a
30a
29a
Dekalb XL-395A (full-season)
0
0.18c
2.47
0.09
0.18
0.10
0.11
1.44
0.11
.003
0.50
48ab
96a
5
0.22b
2.53
0.11
0.19
0.11
0.11
1.43
0.12
.002
0.50
45ab
102a
10
0.26a
2.69
0.11
0.19
0.12
0.11
1.46
0.11
.002
0.50
52a
100a
Means followed by the same letter are not significantly different by Duncans multiple range test at the 0.05 level within each variety.
The MgSO.j.7 FLO foliar sprays and the agricultural
grade MgS04 significantly increased grain yield of the
short-season variety at the 5% level of probability over
the other treatments (Fig. 1). These results warranted
a closer look at the Mg status of the plants. The tissue
analysis of the 21-day old seedlings indicated a Mg
concentration of 0.19% in the short-season variety
(Table 2). While this level is marginal in seedling
corn (Jones, J. B., 1974), it did not concern us as much
as the N and S imbalance. Dolomitic limestone had
been applied to all plots the previous year at the rate
of 4.5 metric tons/ha (approximately 385 kg/ha Mg).
By the time the plants were 55 days old, S concentra
tion had increased in the leaves of plants from the
check plots to 0.17 and 0.18%, which is considered to
be above the critical level for plants of this age (Tables
4 and 5). All of the S treatments increased the S con
centration of the tissue significantly over that of the
check, but did not affect yield of grain or forage. The
N:S ratio had decreased to an average of 11 for the
treated plots and 16 for the check plots. These values
were within the optimum range, indicating an ade
cnate ratio of N and S in the plant tissue. This was
observed in each variety. Flowever, the Mg concentra
tion of the tissue continued to decrease below a critical
level in all treatments. The MgS04.7 FLO foliar sprays
tended to increase the Mg concentration of the tissue,
but these differences were not significant at the 5%
level of probability (Table 5). The significant increase
in yield of the Mg-treated plots of the short-season
variety could have had a dilution effect on the Mg
concentration in the tissue. The same trend in Mg con
centration was observed in the whole-plant samples
of the full-season forage variety (Table 5). However,
neither grain nor total forage yield of the full-season
variety was influenced by any of the treatments. The
depressed yield of Dekalb XL395A by the soil-applied
MgSOj cannot be explained by any of the treatment
variables.
The Mg: total cation ratio in the plant tissue was


43
Proceedings, Volume 39, 1980
Dekalb XL-12 Dekalb XL-395A
Fig. 1.Effect of MgS04 treatments on grain and forage yields
of two co' n cultivars.
calculated, but these values, like Mg, were not very
closely correlated with yield (Tables 4, 5, and 6). The
N:S ratios in whole-plant samples of the forage corn
at harvest were different in samples from treated plots
(ratio=16) and check plots (ratio=18). However, all
values were close enough to the optimum that no sig
nificant differences in yield or quality of the forage
would be expected.
TABLE 6.Mineral analysis of forace at harvest (122 days)
of Dekale XL395A as affected by source and method of appli
cation.
Forage analysis at harvest
Source
Method of
application
S
N
Mg
Ca
Mg:cation
ratio
MgS04.7H,0
foliar
0.08
1.19
0.14
%
0.14
0.28
//
soil
0.08
1.20
0.12
0.15
0.22
k,so4
foliar
0.08
1.22
0.12
0.13
0.26
//
soil
0.08
1.11
0.13
0.13
0.30
CaS04.2H.,0
soil
0.07
1.21
0.13
0.14
0.25
Check

0.07
1.26
0.12
0.13
0.25
Because S is an essential component of plant pro
tein, and protein is one of the important properties
contributing to the quality of forage and grain (Tis
dale, 1977), mineral concentrations of the grain sam
ples were studied (Tables 4 and 5) to evaluate the
effect of S treatments on grain quality. There were no
significant treatment effects on the S, N, or Mg con
centration of the grain samples and no differences in
the N:S ratios or Mg:total cation ratios.
DISCUSSION
Intensive cropping of these plots during 2 years
removed large quantities of nutrients from the soil.
The forage corn system removed 799, 150, 870, and
104 kg/ha of N, P, K, and Mg, respectively, from the
soil over the 2-year period. Dining this same period,
935, 122, 846, and 385 kg/ha of N, P, K, and Mg were
applied (Table 1). No S had been applied to the soil,
but an estimated 63 kg/ha of S was removed in the
forage-corn system. The grain corn system removed
approximately 48 kg/ha S. Since most of the above
ground portion of all crops was removed from the
plots, there was no opportunity for S to be returned to
the soil surface as organic matter. Consequently, S was
TABLE 5.Effect of S source and method of application on yield and leaf and grain analyses
OF TWO CORN CULTIVARS.
Source
Method of
application
Leaf analysis at 55 days
Grain analysis at harvest
Yield
S
N
Mg
Ca
Mgrcation
ratio
S
N
Mg
Ca
Mg:cation
ratio
Grain
Forage
- %
- %
quintal/ha ....
Dekalb XL-12 (short-season)
MgS04.7H.,0
foliar
0.23
2.58
0.13
0.24
0.12
0.10
1.71
0.12
.003
0.48
34a*

//
soil
0.23
2.59
0.10
0.23
0.12
0.11
1.73
0.12
.001
0.47
32a

K..SCL
foliar
0.23
2.40
0.11
0.23
0.12
0.10
1.74
0.12
.002
0.48
24 c

rr
soil
0.24
2.50
0.11
0.24
0.12
0.11
1.70
0.12
.002
0.47
26 be

CaS04.2Ho0
soil
0.24
2.61
0.12
0.24
0.12
0.11
1.69
0.12
.002
0.55
27 be

Check
0.17
2.67
0.10
0.25
0.11
0.11
1.65
0.12
.004
0.49
26 be

Dekalb XL-395A (full-season)
MgS04.7H,0
foliar
0.25
2.56
0.11
0.19
0.12
0.11
1.44
0.12
.001
0.50
49ab
97ab
//
soil
0.22
2.30
0.10
0.20
0.10
0.11
1.55
0.12
.001
0.50
35 b
79 b
k2so4
foliar
0.25
2.65
0.11
0.19
0.11
0.11
1.46
0.12
.002
0.50
48ab
106ab
//
soil
0.23
2.46
0.11
0.21
0.11
0.10
1.47
0.11
.002
0.49
46ab
99ab
CaS0l.2H0
soil
0.26
2.56
0.09
0.20
0.10
0.11
1.51
0.12
.005
0.51
46ab
08ab
Check
0.18
2.47
0.09
0.18
0.10
0.11
1.44
0.11
.003
0.50
47ab
96ab
*Means within varieties followed by the same letter are not significantly different at the 0.05 level by Duncans multiple range test.


44
Soil and Crop Science Society of Florida
depleted from the surface horizons. The preceding
wheat crop had immobilized any available S during
the fall and winter months, and there had been no
opportunity for microorganisms to mineralize soil or
ganic S and the S immobilized in the wheat stubble.
An insufficient amount of soil S was available to the
emerging corn seedlings in the early spring. High rates
of fertilizer N prior to planting antagonized the N:S
imbalance in the young plants. Magnesium uptake was
probably reduced by the high K rates applied prior to
planting. Double-acid extractable Mg averaged 25 ppm
in the upper 30 cm of soil in the experimental area.
All plants were able to grow out of the S-deficient
condition as the roots reached adsorbed S associated
with the argillic horizon in this soil. Soil analyses indi
cated increasing extractable sulfate-S with depth in the
horizon.
0 -15cm (Ap horizon) 2.2 ppm S
15-30cm (A21 horizon) 2.8 ppm S
30-60cm (A22 horizon) 3.5 ppm S
60-80cm (Bt horizon) 16.4 ppm S
Increased mineralization of organic S later in the
season probably also contributed to the improved S
nutrition in the plants.
CONCLUSIONS
Neither foliar sprays of S as potassium sulfate nor
soil-applied S as potassium sulfate or gypsum at 10
kg/ha had any effect on grain or forage yield of Dekalb
XL-12 or Dekalb XL-395A hybrid corn. All S treat
ments increased the S concentration and improved the
N:S: ratio of mature leaves at 55 days in both corn
varieties and in the total plant of the Dekalb XL395A
at harvest. Sulfur treatments had no effect on the
quality or mineral analysis of grain samples of either
variety.
All plants were marginally Mg deficient 21 days
after emergence. As the plants grew out of a S-deficient
condition, Mg became the most limiting nutrient. The
short-season variety (Dekalb XL 12) responded to Mg
in both the foliar spray and in the agricultural-grade
material with increased grain yield. The full-season
variety did not respond to the Mg treatments. This
variable response may be explained by the fact that the
full-season variety was able to utilize more soil Mg and
had a longer period in which to recover from the
stunting of the early-season deficiencies.
LITERATURE CITED
Chaudry, I. A., and A. H. Cornfield. 1966. The determination of
total sulfur in soil and plant material. Analyst 91:528-530.
Ensminger, L. E. 1954. Some factors affecting the adsorption of
sulfate by Alabama soils. Soil Sci. Soc. Am. Proc. 18:259-264.
Fox, R. L., H. M. Atesalp, D. H. Kampbell, and H. F. Rhoades.
1964. Factors influencing the availability of sulfur fertilizers
to alfalfa and corn. Soil Sci. Soc. Am. Proc. 28:406-408.
Jones, J. 15. 1974. Plant analysis handbook for Georgia. Coop.
Ext. Ser. Bul. no. 735. University of Georgia, Athens, Georgia.
Jones, J. B and H. V. Eck. 1973. Plant analysis as an aid in
fertilizing corn and grain sorghum. In L. M. Walsh and J. D.
Beaton (ed.). Soil testing and plant analysis. Soil Sci. Soc.
Am., Madison, Wis.
Jordan, H. V. 1964. Sulfur as a plant nutrient in the southern
United States. Tech. bul. no. 1297. ARS-USDA. Washington,
D.C.
Massoumi, A., and A. H. Cornfield. 1963. A rapid method for
determining sulfate in water extracts of soils. Analyst 88:321-
322.
Neller, J. R. 1952. Sulfur versus phosphorus for soils in pastures
of Florida. Soil Sci. Soc. Florida Proc. 12:123-127.
. 1959. Extractable sulfate-sulfur in soils of Florida in
relation to amount of clay in the profile. Soil Sci. Soc. Am.
Proc. 23:346-348.
Neller, J. R., G. B., Killinger, D. W. Jones, R. W. Bledsoe, and
H. W. Lundy. 1951. Fertilizer should contain a source of
sulfur for clover pastures in many areas of Florida. Agri. Exp.
Sta. Cir. S-35. University of Florida, Gainesville, Florida.
Stewart, B. A., and K. L. Porter. 1969. Nitrogen-sulfur relations
in wheat (Triticum aestivum), corn (Zea mays), and beans
(Pliaseolus vulgaris). Agron. J. 61:267-271.
Teman, G. L., S. E. Allen, and P. M. Giordano. 1973. Dry matter
yieldN and S concentration relationships and ratios in young
corn plants. Agron. J. 65:633-636.
Tisdale, S. L. 1977. Sulfur in forage quality and ruminant nuti-
tion. Tech. bul. no. 22. The Sulphur Institute. Washington,
D. C.
The Response of the Three Perennial Warm-Season Grasses
to Fertilizer Nitrogen on Eaugallie Fine Sand
(Alfic Haplaquod) in Central Florida1
W. G. Blue, C. L. Dantzman, and V. Impithuksa2
ABSTRACT
Three warm-season perennial grassesPensacola
bahiagrass (Paspalum notatum Fliigge), Ona stargrass
(Cynoclon nlemfuensis Vanderyst var. nlemfuensis), and
Transvala digitgrass (Digitaria decumbens Stent.)
were compared for response to applied N on EauGallie
fine sand (Alfic Haplaquod) at the Agricultural Re-
iFlorida Agricultural Experiment Stations Journal Series No.
2250.
^Professor, Soil Science Department; Associate Professor, Agri
cultural Research Center (Ona); and former graduate student,
Soil Science Department (presently Assistant Professor, Soil Sci
ence Department, Kasetsart University, Bangkok, Thailand), re
spectively, University of Florida, Gainesville, FL 32611.
search Center, Ona, Florida. The experiment was a
split-plot design with plant species as main plots and
N rates0, 112, 224, and 336 kg/ha/yearas subplots.
Lime, S, and micronutrients were applied uniformly,
and P and K in a 2:0.4:1.6 ratio with the N applied.
Forage was harvested four times/year, and macro
nutrients were applied two times/yearone half at the
beginning of the growing season in March and one
half after the second harvest approximately 1 July.
Grasses were planted on 3 October 1974; differential
fertilization and forage harvests were made from 1975
through 1979. Forage yields were very large in 1975,
especially from Ona stargrass and Transvala digitgrass,
compared with succeeding years. Forage N contents for


45
Proceedings, Volume 39, 1980
1975 were also large compared with succeeding years;
they were approximately two times as large from Ona
stargrass and Transvala digitgrass as from the Pensa
cola bahiagrass. Stolon-root mass and N content at the
end of 1975 from Pensacola bahiagrass were approxi
mately twice those from Ona stargrass and four times
those from Transvala digitgrass. Biomass yields from
Pensacola bahiagrass and Ona stargrass for 1975 were
larger than from Transvala digitgrass, but biomass N
was larger from Ona stargrass than from Pensacola
bahiagrass and Transvala digitgrass. The large bio
mass production and N contents during the first year
were primarily a consequence of enhanced mineraliza
tion of soil N following application of lime and dis
turbance of this virgin soil. Subsequently, forage pro
duction and N contents were comparable to those
from other long-term experiments; growth response to
N rates differed for the three grasses, but maximum
forage yields were similar. Stolon-root mass from Pensa
cola bahiagrass at the end of each season was approxi
mately twice that from Ona stargrass and three times
that from Transvala digitigrass. In spite of differences
in stolon-root masses, forage N contents of the three
species in response to increasing N rates were not dif
ferent and can be represented by the equation
Y = 25.3 + 0.397X + 0.0003X2
where Y = forage N contents and X = N applied,
each expressed as kg/ha.
Additional Index Words: Paspalum notatum
Flgge, Cynodon nlemfuensis Vanderyst var. nlem-
fuensis, Digitaria decumbens Stent., Spodosol, Nitro
gen uptake, Stolon-root mass, Biomass.
We have been studying N use efficiency primarily
by Pensacola bahiagrass (Paspalum notatum Flgge)
on Florida Spodosols and Entisols intensively for the
past 20 years. Several factors which can affect N losses
are leaching, denitrification, and NH3 volatilization.
Soil pH control, N sources, N rates, multiple N appli
cations, seasonal timing of N applications, effect of
stolon-ioot mass, rate of N absorption by plants, and
annual N fertilization repeated over several years have
been studied (1, 2, 3, 5, 6, 8, 9). These factors could
ultimately affect N utilization by plants. Of these, only
repeated annual N fertilization has given increased
N-use efficiency. Increased N uptake with time was
due in part to development of a relatively stable
stolon-root mass with respect to immobilization of N
and perhaps to mineralization of N immobilized
temporarily in soil organic matter.
Pensacola bahiagrass develops a large stolon-root
mass with N rates of 100 kg/ha/year or more. Nitrogen
concentrations and contents in the stolon-root mass
depend on N rates (4). Nitrogen absorption rates are
dependent on N application rate and may be as high
as 6 kg/ha/day (8). This absorbed N, depending on
temperature and soil moisture, may be stored in the
stolon-root system and translocated as needed for top
growth. Many perennial grass species that have been
introduced have smaller, less permanent stolon-root
massees than the bahiagrass. Differences in plant
morphology could affect N absorption rates, partic
ularly during adverse climatic periods for plant growth.
The objectives of this experiment were to compare
Pensacola bahiagrass which has a large, relatively
permanent stolon-root mass with two speciesOna
stargrass (Cynodon nlemfuensis Vanderyst var. nlem
fuensis) and Transvala digitgrass (Digitaria decumbens
Stent.)which have smaller, less permanent systems for
growth response to fertilizer N and N uptake in plant
components.
MATERIALS AND METHODS
The experiment was established on virgin Eau-
Gallie fine sand (sandy, siliceous, hyperthermic Alfic
Haplaquod) at the Agricultural Research Center (Ona)
in central Florida. A cultivar of each of three grass
speciesPensacola bahiagrass, Ona stargrass, and
Transvala digitgrassconstituted the main plots which
were 5 X 10 m. Four N rates were the subplots and
were 2.5 X 5 m. There were four replications. Borders
between replications were 3 m wide.
The soil received 3.75 metric tons/ha each of
calcitic and dolomitic lime on 15 August 1974 prior to
planting the grasses on 3 October; 54, 12, and 22 kg of
N, P, and K/ha, respectively, were applied on 10
October following planting. A micronutrient frit was
applied uniformly to all plots also on 10 October 1974
at 34 kg/ha and gypsum was applied annually at 240
kg/ha to supply adequate S. Nitrogen was applied
annually at rates of 0, 112, 224, and 336 kg/ha as
NH.jNOj with one half applied during the latter part
of March and one half following the second forage
harvest on approximately 1 July. Phosphorus as triple
superphosphate and K as KC1 were applied with the
N to give a N:P:K ratio of 2:0.4:1.6 (N:P205:K20
ratio of 2:1:2); the 0 and 112 kg/ha N rates received
the same amounts of P and K. Forage was harvested
four times per year as nearly as possible to 15 May, 1
July, 10 August, and 1 October. Pensacola bahiagrass
was harvested to a 3-cm stubble while Ona stargra
and Transvala digitgrass were cut 7 cm above the soil
surface. Stolon-root samples were collected after the
fourth forage harvest on 1 October of each year. Stolon-
root samples were washed thoroughly with tap water
and rinsed in distilled water to remove soil. All plant
tissues were dried at 70 C, ground by a Wiley mill to
pass a 20-mesh screen, and analyzed for total N by a
micro-Kjeldahl method which employed salicylic acid
and sodium thiosulfate for reduction of nitrates.
Data were analyzed statistically by analyses of vari
ance; treatment means were compared with Duncans
new multiple range test.
RESULTS AND DISCUSSION
Forage yields were relatively large in 1975 for each
of the grasses at all N rates, and particularly so from
Ona stargrass and Transvala digitgrass (Table 1).
Nitrogen contents of forage were also large. This was
not only a consequence of the fertilizer N, but also of
rapid mineralization of a fraction of the soil N after
application of lime and disturbance of this virgin
soil (7). In contrast to forage production, the stolon-
root mass from Pensacola bahiagrass at the end of
1975 was approximately two times that from Ona star-
grass and four times that from Transvala digitgrass.
Quantities of N in stolon-root systems were in approxi
mately the same proportion as stolon-root masses. Bio
masses from Pensacola bahiagrass and Ona stargrass


46
Soil and Crop Science Society of Florida
TABLE 1.Yield and nitrogen uptake by three perennial, warm-season grasses in response to
FERTILIZER N ON EAUGALLIE FINE SAND.
Annual
1975
Average 1976-79
Total
N
Plant species
rate
PB
Ona Trans
Avg
PB
Ona Trans
Avg
PB
Ona Trans
Avg
kg/ha Oven-dry forage, kg/ha
0
112
224
336
Avg
4690
8220
9030
10940
8220c
11490
17450
17670
20260
16720a
10770
14990
14780
14690
13810b
8980cf
13550b
13830ab
15300a
2600
6020
10110
13580
8080b
0
14630
8440
3600
8890a
13070
112
16170
9580
3920
9890a
19460
224
14030
8720
3560
8770a
21570
336
17170
5820
3850
8950a
20780
Avg
15500a
8140b
3730c
18720a
2010
3660
2760d
15050
19550
25400
20000d
5530
8240
6600c
32300
39600
47950
39950c
9460
11860
10480b
49500
55500
62200
55730b
11790
12720
12700a
65250
67400
65550
66070a
7200b
9120a
40530c
45510b
50280a
dry stolons + roots, kg/ha
6150
6120
8450b
8480
7570
11840a
9130
6660
12450a
6880
5180
10950a
7660b
6380b
0
19330
19930
14370
17880b
29000
23720
32290
28340a
112
24390
27030
18910
23440a
51490
47260
55810
51520c
224
23060
26390
18340
22600a
71420
63240
62200
65620b
336
28110
26080
18540
24240a
87050
73330
65550
75310a
Avg
23720a
24860a
17540b
59740a
51890b
53960ab
Forage N, kg/ha .
0
51
105
99
85d
28
21
31
27d
165
185
220
190d
112
114
204
170
163c
70
64
78
71c
394
460
483
446c
224
131
246
188
188b
130
130
138
133b
695
770
740
735b
336
178
279
226
228a
194
197
184
192a
955
1070
965
997a
Avg
119c
209a
171b
106a
103a
108a
552b
621a
602a
Stolon-root
N, kg/ha
0
51
41
16
36b
45
32
24
34d
112
72
51
21
48ab
72
50
36
53c
224
86
54
20
53ab
105
69
38
71b
336
137
38
24
66a
142
57
35
78a
Avg
87a
46b
20b
91a
52b
33c
Biomass N, kg/ha
0
102
146
115
121c
217
201
245
22 Id
112
186
255
191
211b
466
501
518
495c
224
217
300
208
242b
818
829
775
807b
336
315
317
250
294a
1110
1118
1002
1077a
Avg
205b
255a
191b
653ab
662a
635b
(Means within columns and lines within subtables followed by the same letter are not significantly different at the 0.05 probability
level according to Duncans new multiple range test.
for the first year were approximately the same and
substantially larger than the biomass from Transvala
digitgrass. Utilization of photosynthate and N for
production of the larger stolon-root mass by Pensacola
bahiagrass obviously reduced forage production dur
ing the developmental period in comparison with the
other two grasses which have relatively small stolon-
root systems.
For years 1976 through 1979, forage production
from the three grasses at the highest N rate was not
significantly different, but production at other N rates
did differ. Response of the three grasses to N rates can
be characterized by the following equations where
Y = oven-dry forage yields and X = N rates, both
expressed as kg/ha.
Forage plants Regression equations
Pensacola bahiagrass Y = 2530 + 32.8X + 0.00IX2
Ona stargrass Y = 1920 + 37.2X 0.022X2
Transvala digitgrass Y = 3610 + 54.1X 0.081X2
Growth response characteristics of the three grasses
were likely related to absorption and storage of N in
the stolon-root systems, and perhaps to some N im
mobilization in dead, partially decomposed stolon-root
tissues. Thus, forage production from Transvala digit-
grass with the smallest stolon-root system was largest
at low N rates and from Pensacola bahiagrass the
smallest.
Nitrogen uptake in forage from 1976 through 1979
did not differ significantly among forage plants and
can be characterized by a single equation as follows
where Y = forage N and X = N applied, both ex
pressed as kg/ha.
Y = 25.3 + 0.397X + 0.0003X2
Stolon-root masses from Pensacola bahiagrass and
Transvala digitgrass increased somewhat from 1976
through 1979 in comparison with masses at the end of
1975, while Ona stargrass did not change appreciably.
Biomass production through 5 years, i.e., total
forage produced over the 5-year period plus stolon-root
mass at the end of the fifth year, was not drastically


47
Proceedings, Volume 39, 1980
different for the three grasses, but was significantly
larger from Pensacola bahiagrass than from Ona star-
grass. Biomass N for the three grasses through 5 years
was also similar.
Ona stargrass did not maintain a satisfactory stand
under the experimental conditions through the 5-year
period in comparison to Pensacola bahiagrass and
Transvala digitgrass. Since stolon-root samples were
taken only where grasses were present, stolon-root mass
and biomass from Ona stargrass were somewhat over
estimated.
LITERATURE CITED
1. Blue, W. G. 1966. The effect of nitrogen sources, rates, and
application frequencies on Pensacola bahiagrass forage yields
and nitrogen utilization. Soil and Crop Sci. Soc. Florida Proc.
26:105-109.
2. Blue, W. G. 1970. Fertilizer nitrogen uptakes by Pensacola
bahiagrass (Paspalum notatum) from Leon fine sand, a
Spodosol. XI Int. Grassland Congr. Proc., Surfers Paradise,
Australia. 389-392.
3. Blue, W. G. 1972. Nitrogen fertilization in relation to seasonal
Pensacola bahiagrass forage nitrogen and production distribu
tion. Soil and Crop Sci. Soc. Florida Proc. 31:75-77.
4. Blue, W. G. 1973. The role of Pensacola bahiagrass stolon-
root systems in fertilizer nitrogen utilization on Leon fine
sand. Agron. J. 65:88-91.
5. Blue, W. G. 1974. Efficiency of five nitrogen sources for
Pensacola bahiagrass on Leon fine sand as affected by lime
treatments. Soil and Crop Sci. Soc. Florida Proc. 33:171-180.
6. Blue. W. G. 1977. Comparison of sulfur-coated urea and am
monium nitrate for Pensacola bahiagrass on a Florida
Spodosol. Soil Sci. Soc. Am. J. 41:1191 -1193.
7. Blue, W. G., C. F. Eno, N. Gammon, Jr., and D. F. Rothwell.
1964. Timing liming applications to obtain the maximum
beneficial effect in clover-grass pasture establishment on
virgin flatwoods soil. Soil and Crop Sci. Soc. Florida Proc.
24:162-166.
8. Blue, W. G., and D. A. Graetz. 1977. The effect of split nitro
gen applications on nitrogen uptake by Pensacola bahiagrass
from an Aerie Haplaquod. Soil Sci. Soc. Am. J. 41:927-93(1.
9. Mata, A., and W. G. Blue. 1974. Fertilizer nitrogen distribu
tion in Pensacola bahiagrass sod during the first year of de
velopment on an Aerie Haplaquod. Soil and Crop Sci. Soc.
Florida Proc. 33:209-211.
Mobility and Extractability of Phosphorus
Applied to the Surface of Tifway Bermudagrass Turf1
J. B. Sartain2
ABSTRACT
A field-plot experiment was initiated on Tifway
bermudagrass [Cynodon dactylon (L.) Pers.] turf to
study the effect of time on the extractability of P by
different soil extractants and to evaluate the extent of
downward movement of applied P. Three replications
of five rates of P (0, 98, 197, 394, and 788 kg/ha) were
established in a randomized complete block design on
3 by 4 m plots. Soil samples were collected monthly
during the first 6 months and approximately every 45
days during the remainder of the 15-month sampling
period. Each sample was divided into three sections by
depth (0 to 5, 5 to 20, and 20 to 30 cm). Phosphorus
status of each sample was determined in the following
extractants: IN NH4C1; 0.0021V H,S04; NH4OAc, pH
4.8; 0.0251V H2S04 in 0.05V HC1; and 0.03 N NH4F in
0.11V HC1. Total P was determined on selected sam
plings by the perchloric acid procedure.
Readily extractable NH4C1-P equilibrated with the
soil within the first 6 months of the 98 kg/ha P appli-
tions and was reduced to extractable levels near those
of the control plots. Ammonium chloride extractable
P was reduced by 70% during the first 6 months but
had not reached the P level extracted prior to the ap
plication of 788 kg/ha P. Truog, NH4OAc, and double
acid extractable P decreased by similar percentages
during the first 6 months, but only about 30 % as much
as the NH4C1-P n plots receiving 98 kg/ha P. Double
acid and Bray-2 extractable P had not stabilized 15
months after 788 kg/ha P was applied. Small increases
in readily extractable and double-acid P were noted at
iFlorida Agricultural Experiment Stations Journal Series No.
2259.
2Associate Professor of Soil Fertility (Turf and Ornamentals),
Soil Science Department, University of Florida, Gainesville, FL
32611.
the 5 to 20-cm depth from the application of 98 kg/ha
P. Large increases in the double-acid soluble P were
observed after 3 months at the 5 to 20-cm depth where
788 kg/ha P were applied. Phosphorus did not leach
below the 20-cm zone during the first 15 months.
Additional Index Words: Extractable P, Readily
soluble P, Total P, Soil phosphate complexes.
Phosphorus accumulation has been studied in many
soils as part of the problem of assessing P availability
to crops. The usually small amount of accumulated P,
relative to the larger amounts of native P in phosphatic
soils, has prevented an accurate evaluation of the forms
in which P compounds exist.
Dicalcium phosphate (DCP) was shown to be a
major initial product in soils that had received mono
calcium phosphate (MCP). This product (DCP) forms
by hydrolysis around granules of MCP (10). The re
sultant acidity solubilized appreciable Ca, Al, Fe, and
Mn (10). These dissolved ions were shown to be in
corporated in subsequent P precipitation (10).
In laboratory tests, Yuan et al. (19) reported that
applications of water-soluble P quickly reverted to the
Al forms in three sandy Florida soils. Fiskell and
Rowland (5) used sequential extractions and total
analysis to show that Al and Fe phosphates were the
major forms present in both phosphatic and non-
phosphatic Florida soils.
Aluminum-P is the fraction most commonly re
ported as being correlated with plant-available P on
acid to nearly neutral soils (7, 11, 15). The Ca-P form
contributes significantly to the P supply on recently
fertilized soils and acid soils fertilized with rock phos
phate (4).
The extractability of various P fractions can be


48
Soil, and Crop Science Society of Florida
summarized according to the principle ions used in the
soil extractant. Hydrogen ions remove fractions in the
order Ca-P > Al-P > Fe-P; hydroxide ions in the order
Fe-P > Al-P; bicarbonate ions in the order Al-P > Fe-P
Ca-P; fluoride ions in the order Al-P > Fe-P > Ca-P;
and acetate ions in the order Al-P > Ca-P > Fe-P (3,
6, 11, 12, 15, 16).
Humphreys and Pritchett (8) reported little or no
residual P from superphosphate remained in the top
20 cm of soils with little P sorption or buffering capac
ity, such as a Leon fine sand over a period of 7 to 10
years. Almost all of the applied P remained as an avail
able form in the rooting zone in soils with a low P
sorption and buffering capacity; whereas, in a soil with
high P sorption and buffering capacity, most of the
added P was retained in the surface horizon in forms
of limited availability. Ballard and Fiskell (2) reported
that most of the sandy soils of the Southeastern Coastal
Plains have a very small retention capacity for water-
soluble P against leaching, but that the surface hori
zons of Spodosols had the lowest retention capacities.
Linear adsorption isotherms were reported for most of
the Spodosols, but isotherms for Ultisols, Inceptisols,
and Entisols were non-linear. In a lysimeter study,
Neller (13) reported that in 4 months 72.4 cm of rain
fall leached more than 70% of applied superphosphate-
P from the surface 20 cm of a Leon fine sand.
The objectives of this study were: (1) to determine
the effect of time on the quantity of P extracted by dif
ferent extractions; and (2) to determine the extent of
downward movement of P applied to the surface of
bermudagrass [Cynodon dactylon (L.) Pers.] turf.
MATERIALS AND METHODS
Experimental 3 x 4 m plots were established on a
healthy stand of Tifway bermudagrass at the Horti
cultural Unit near Gainesville in a randomized com
plete block design. Three treatment replications of P
were applied at 0, 98, 197, 394, and 788 kg/ha as con
centrated superphosphate. Phosphorus was applied in
solution at 16 liters per plotthis volume permitted
uniform coverage of the 12 m2 with minimum penetra
tion of the soil profile. Nitrogen and K were applied at
an annual rate of 400 and 200 kg/ha as NH4N03 and
KC1, respectively, to all plots.
Soil samples were collected every 30 days during the
first 6 months after treatment application and approxi
mately every 45 days during the succeeding 9 months.
The ten cores of each sampled profile were divided into
three sections0 to 5, 5 to 20, and 20 to 30 cm. All
samplings for the 15-month period were analyzed for
P by extraction with the solutions listed in Table 1.
Total P by the perchloric acid oxidation procedure
(9) was determined on selected samplings. Only data
involving the 98 and 788 kg/ha P treatments are dis
cussed in this study because of the large volume of data
obtained. The other P treatments showed similar
trends.
The soil on which the bermudagrass was established
is an Arredondo fine sand (loamy, siliceous, hyper
thermic family of Grossarenic Paleudult) which has a
high total native P status. A few weathered and leached
phosphatic pebbles ranging in diameter from 2 to
20 mm were found scattered throughout the profile.
Chemically this soil had a pH of 6.1, CEC of 9.6, and a
negligible level of IN KC1 extractable Al.
TABLE 1Phosphorus extraction methods.
Method
Extractant
pH
Soil:
Solu
tion
Shaking
Time
Ref.
NH Cl
4
IN NH Cl
4
3.0
1:10
minutes
30
16
T ruog
0.002N H,S04 +
3g(NH4)S04/l
3.0
1:100
30
17
NH.OAc
4
0.7N NH4OAc +
0.5N CH3CooH
4.8
1:5
30
14
Double-acid
0.05N HCI +
0.025N H2S04
1.3
1:4
5
14
Bray-2
0.03N NH4F +
0.1N HCI
1.3
1:10
1
14
Total P
HCIO.
4
-
1:10
-
9
RESULTS AND DISCUSSION
Soil P status prior to treatment application for
three segments of the top 30 cm of the profile is given
in Table 2. Ammonium chloride extractable P was
shown to correlate strongly (r = .95) with the water-
soluble P fraction of the soil (16). The top 5 cm con
tained a relatively high level (4 ppm) of NH4C1-
soluble P, while less P was soluble at the two lower
depths. Previously applied fertilizer P could account
for the observed P status of the surface sample. Truogs
solution (0.002N H2S04) removed more P than IN
NH.jCl. Researchers (18) in the past have correlated
Truog extractable P with portions of the Ca-P and
Al-P fractions. Ammonium acetate, pH 4.8 solubilized
approximately twice as much P as 0.002N H2S04 in
the top 5 cm and about three times as much in the 5
to 20 and 20 to 30-cm sections. Acetate ions reportedly
solubilize more Al-P than do H ions (1). Since the
high P status of the 0 to 5-cm section was most likely
due to the application of Ca-P and a higher proportion
of Al-P was probable at the lower soil depths, the
greater relative P solubility with NH4OAc, pH 4.8 at
the lower depths could have been due to Al-P.
Mehlichs double-acid extractant solubilized more than
five times as much P as did the NH4OAc, pH 4.8 in
the surface 5 cm. The lower pH (1.3) of the double
acid extractant and its stronger affinity for dissolution
of Ca-P accounted for this increased P extraction.
Bray-2 extractant is reported to solubilize more Fe-P
TABLE 2.Soil P status prior to treatment application by
DIFFERENT EXTRACTANTS AND DEPTHS.
Depth (,cm)
0 to 5 5 to 20 20 to 30
IN NH4C1
0.002N HS04
NH4OAc,pH 4.8
0.05N HC1 in 0.025N H.,S04
0.03N NH4F in 0.1N HCI
Total P
P, ppm (%)f
4.4 (0.5) 0.5 (0.07) 0.6 (0.09)
17.1 (2) 4.7 (0.7) 4.5 (0.7)
34.0 (4) 12.8 (2) 12.9 (2)
191.9 (23) 117.4 (18) 104.4 (17)
335.5 (41) 281.7 (44) 234.7 (38)
882.3 637.7 614.4
fEntries in parenthesis are percentages of total P.


49
Proceedings, Volume 39, 1980
and Al-P than the other extractants because of the
acid strength and the presence of the complexing
fluoride ions (1). Approximately the same amount (ca
40%) of the total P was removed by the Bray-2 ex
tractant at all three soil depths. Since this extractant
solubilized proportionally more Fe-P and Al-P and the
quantity of free Fe and A1 was typically low in this
soil, most of the P remained in the Ca-P form and was
not readily solubilized by the Bray-2 extractant. Total
P reserves in this soil prior to the initiation of the
study were very high and the probability of a response
to applied P fertilizer was small.
One month after application of 98 kg/ha of P as
TSP, the NH.jCl-P in the 0 to 5-cm layer was 10 ppm
higher than prior to addition of P (Table 3). During
the following 6 months, the readily soluble P level
dropped by 53% to near the level prior to application,
indicating that the MCP contained in the TSP was
gradually converted to more insoluble P forms. Phos
phorus solubility by Truog, NH,OAc, and double-acid
extractants decreased by similar percentages during
the first 6 months despite the large differences in the
quantities of P extracted. The relatively small reduc
tion of the Truog P (which has been shown to corre
late with Ca-P, such as DCP) suggested that a signif
icant portion of the P at the end of 6 months was still
in a dilute acid soluble form. Bray-2 extractable P was
not significantly reduced during the first 6 months. A
very small portion of the applied P was converted to
sparingly soluble P forms of adsorbed or occluded P.
Total P decreased by 0.1% in the top 5 cm which was
probably the resultant of plant uptake.
The data for the 15-month sampling period can be
divided into two distinct groups (Table 3). Most of
the change in the readily soluble P occurred within
the first 6 months. During the 9 to 15-month period,
the level of P solubilized by the dilute acid and salt
extractants remained static. Bray-2 was reduced by ap
proximately 11% during the 9 to 15-month period in
dicating that change was still occurring in the more
insoluble A1 and Fe-P compounds.
Almost identical trends in P solubility were ob
served during the first 6 months in plots receiving a
high level (788 kg/ha) of P (data not shown). The
primary difference between the 788 and 98 kg/ha P
treatments was the magnitude of the reduction in ex
tractable P status with time. Since a larger decrease in
total P was observed (8.2%), it was suggested that a
significant portion of the reduction in P status for all
extractants was due to the downward displacement of
the applied P.
Where P was applied at a typical rate (98 kg/ha),
the level of NH4Cl-soluble P did not increase greatly
in the sampled sections below 5 cm (Table 4). The
slight increase in NFI.,Cl-extractable P in the 5 to 20-cm
section could have resulted from the method of appli
cation. The treatments were applied in solution; there
fore, the P may have moved with the water during
initial treatment even though the P was applied in 16
liters of solution to the 12 m2 area. Initial application
conditions do not explain the changes which occurred
with time by depth in the NH4C1-P on plots receiving
788 kg/ha P since a high level of P was not detected at
the 25 March sampling. Soil NH4Cl-extractable P in
creased in the 5 to 20-cm section during the first 4
months after application, indicating the downward
movement of P from the surface and retention of this
readily soluble P fraction in the 5 to 20-cm zone. At no
TABLE 3.Effect of time on the solubility of P with a low level of applied P.
Months 1 thru 6 Months 9 thru 15
Sampling dates (1976) % Sampling dates (1976-77) %
Extractant
25 Mar
22 Apr
20 May
25 June
19 Aug
reduction
3 Nov
15 Dec
2 Mar
25 May
reduction
_ P, ppm .
P,
ppm
nh4ci
14.2
12.9
13.5
10.0
6.6
53.5
5.2
4.8
7.1
5.9
0
T ruog
30.2
29.3
33.7
32.3
26.0
14.0
23.3
22.7
25.5
21.8
6.4
NH(OAc
52.0
48.7
54.0
42.6
42.6
18.1
40.0
39.7
38.9
40.6
0
Double acid
266.7
212.3
258.1
261.8
226.2
15.2
216.7
223.8
215.2
220.5
0
Bray 2
406.8
401.3
384.0
384.0
396.3
2.3
386.2
320.7
362.6
344.0
10.9
Total P

863.9

875.2
855.7
0.1
843.7


832.5
1.3
Sampling Depth: 0 to 5 cm
P Application: 98 kg/ha
TABLE 4.Downward movement of NH.CI-soluble P in response to two levels of applied P
4
WITH TIME.
P Sampling dates (1976-77)
Depth
Applied
5 Feb
25 Mar
22 Apr
20 May
25 June
19 Aug
3 Nov
15 Dec
2 Mar
25 May
cm
kg/ha
P,
0 to 5
98
4.5
11.1
12.9
13.5
10.0
6.6
5.2
4.8
7.1
5.9
5 to 20
98
0.3
0.6
0.8
0.9
0.6
0.9
0.7
0.6
0.6
0.6
20 to 30
98
0.4
0.1
0.9
0.5
0.5
0.5
0.5
0.1
0.4
0.2
0 to 5
788
4.2
82.4
69.4
47.4
36.4
24.2
19.2
19.6
20.5
14.3
5 to 20
788
0.3
1.4
4.0
6.1
6.0
3.8
3.7
4.6
3.7
5.6
20 to 30
788
0.4
0.2
1.0
0.6
0.4
0.6
0.5
0.2
0.6
0.1


50
Son. and Crop Science Society of Florida
TABLE 5.Downward movement of double-acid soluble P in response to two levels of applied
P WITH TIME.
P Sampling dates (1976-77)
Depth
Applied
5 Feb
25 Mar
22 Apr
20 May
25 June
19 Aug
3 Nov
15 Dec
2 Mar
25 May
cm
kg/ha
P;
0 to 5
98
195
267
212
258
262
226
217
223
215
220
5 to 20
98
108
118
117
105
112
131
115
123
129
104
20 to 30
98
95
87
90
87
89
97
93
104
99
95
0 to 5
788
209
851
790
753
707
528
499
552
489
386
5 to 20
788
136
182
159
255
266
228
235
252
233
233
20 to 30
788
87
77
74
75
74
91
83
105
87
94
sampling time during the 15-month period was an in
crease in NH.jCl-extractable P observed in the 20 to
30-cm section.
Small and erratic fluctuations o£ the double-acid P
status of the 5 to 20-cm zone were noted where 98
kg/ha P was applied (Table 5). These increases and
decreases in P status may have been influenced more
by the environment and plant uptake than by the
movement of P through the profile. Plots receiving
788 kg/ha P had not equilibrated with respect to
double-acid soluble P in the 0 to 5-cm layer even after
15 months. After about 3 months, the double-acid
soluble P level reached a maximum in the 5 to 20-cm
section and began to decrease with time, but not to
the P level prior to P application. No change in the P
status of the 20 to 30-cm section was observed for
either the high or low P application. A more informa
tive sampling would have involved the division of the
5 to 20-cm section into more than one section and the
exclusion of the 20 to 30-cm zone.
LITERATURE CITED
1. Ballard, R. 1974. Extractability of reference phosphates by
soil test reagents in absence and presence of soils. Soil Crop
Sci. Soc. Florida Proc. 33:169-174.
2. Ballard, R., and J. G. A. Fiskell. 1974. Phosphorus retention
in Coastal Plain Forest Soils: 1. Relationship to soil prop
erties. Soil Sci. Soc. Am. Proc. 38:250-255.
3. Chang, S. C., and S. R. Juo. 1963. Available phosphorus in
relation to forms of phosphorus in soils. Soil Sci. 95:91-96.
4. Chu, C. R., W. W. Moschler, and G. W. Thomas. 1962. Rock
phosphate transformations in acid soils. Soil Sci. Soc. Am.
Proc. 26:476-478.
5. Fiskell, J. G. A., and L. O. Rowland. 1960. Soil chemistry of
subsoils of west central Florida. Soil Crop Sci. Soc. Florida
Proc. 20:123-128.
6. Grigg, J. L. 1965. Inorganic phosphorus fractions in South
Island soils and their solubility in commonly used extracting
solutions. N. Z. J. Agrie. Res. 8:313-326.
7. Grigg, J. L. 1968. Prediction of plant response to fertilizer by
means of soil tests: II. Correlations between soil phosphate
tests and phosphate response to ryegrass grown in pot experi
ments on recent, gley recent, and gley soils. N. Z. J. Agrie.
Res. 11:345-358.
8. Humphreys, F. R., and W. L. Pritchett. 1971. Phosphorus
adsorption and movement in some sand forest soils. Soil Sci.
Soc. Am. Proc. 35:495-500.
9. Jackson, M. L. 1958. Soil chemical analysis. Prentice-Hall,
Inc. Englewood Cliffs, N. J.
10. Lindsay, W. L., A. W. Frazier, and H. F. Stephenson. 1962.
Identification of reaction products from phosphate fertilizers
in soils. Soil Sci. Soc. Am. Proc. 26:446-452.
11. Martens, D. C., J. A. Lutz, and G. O. Jones. 1969. Form and
availability of P in selected Virginia soils as related to avail
able P tests. Agron. J. 61:616-621.
12. McLachlan, K. D. 1965. The nature of available phosphorus
in some acid pasture soils and a comparison of estimating
procedures. Aust. J. Expt. Agrie. An. Husb. 5:125-132.
13. Neller, J. R. 1946. Mobility of phosphates in sandy soil. Soil
Sci. Soc. Am. Proc. 11:227-230.
14. Page, N. R., G. W. Thomas, H. F. Perkins, and R. D. Rouse.
1965. Procedures used by state soil-testing laboratories in the
southern region of the United States. Southern Cooperative
Series Bull. No. 102.
15. Payne, H., and W. J. Hanna. 1965. Correlations among soil
phosphorus fractions, extractable phosphorus, and plant con
tent of phosphorus. J. Agrie. Food Chem. 13:322-326.
16. Pratt, P. F., and M. J. Garber. 1964. Correlations of phos
phorus availability by chemical tests with inorganic phos
phorus fractions. Soil Sci. Soc. Am. Proc. 28:23-29.
17. Sherreli, C. G. 1970. Comparison of chemical extraction
methods for the determination of available phosphate in
soils: I. Correlation between methods and yield and phos
phorus uptake by white clover grown on the 16 North Island
soils in the glasshouse. N. Z. J. Agrie. Res. 13:481-493.
18. Susuki, A., K. Lawton, and E. C. Doll. 1963. Phosphorus up
take and soil tests as related to forms of phosphorus in some
Michigan soils. Soil Sci. Soc. Am. Proc. 27:401-403.
19. Yuan, T. L., W. K. Robertson, and J. R. Neller. 1960. Forms
of newly fixed phosphorus in three acid sandy soils. Soil Sci.
Soc. Am. Proc. 24:447-450.


Proceedings, Volume 59, 1980
51
Growth Responses of Young Slash Pine to Site Preparation
and Fertilization on Poorly Drained Soils1
W. L. Pritchett and E. G. Flaig2
ABSTRACT
Seven uniform experiments were established on a
range of poorly drained soils in the lower coastal plain
to evaluate the effects of site preparation on survival
and early growth of slash pine (Pinus elliottii var.
elliottee Engelm.) and the feasibility of substituting
fertilization for the more expensive site preparation
practices. Tree heights were significantly increased by
the more intensive preparation treatments (disking
and bedding) and by fertilization with P and N + P, 5
to 8 years after treatment. There were no interactions
between the two types of treatments and their effects
were generally additive. Tree growth rates declined on
bedded plots, in relation to control plots, after 5 years.
Response to fertilizers also declined on some soils, but
early differences in heights were maintained for at
least 8 years. There were relatively few significant
effects of treatments on nutrient concentrations in
needles, except for P. Double-acid extractable A1 was
significantly decreased by site preparation of Ultic
Haplaquods. Bulk density was slightly increased by
chopping in three of nine selected blocks, but bedding
had no significant effect on bulk density after 8 years.
At this stage of plantation development, total biomass
of understory vegetation did not differ significantly
among treatments.
Additional Index Words: Forest nutrition, Forest
soils, Phosphate fertilization, Bedding, Pinus elliottii.
Forest management in the southeastern United
States stresses the regeneration of pines in plantations,
and approximately 8 million hectares of pine are pres
ently grown in plantations in the area. Plantation
forestry allows the use of heavy equipment for slash
reduction, soil amelioration, and facilitation of plant
ing. Slash pine (Pinus elliottii var. elliotlii Engelm.), a
fast growing, shade-intolerant species, responds well to
evenaged, intensive plantation management. This
often involves the use of machinery for seedbed prep
aration, a practice used on many sites to insure ade
quate seedling survival and early tree growth, and to
reduce competing vegetation.
Shearing blades, rootrakes, and disk harrows are
often used in site preparation, particularly on sites
with considerable hardwood vegetation. However,
these operations not only reduce competing vegetation,
but may also drastically disturb the surface soil and
the blades and rakes may remove much of the forest
floor and surface soil organic matter into windrows.
While these treatments often improve seedling survival
and early growth as a result of reduced competition
from understory vegetation and increased soil nutrient
iFlorida Agricultural Experiment Stations Journal Series No.
2283.
2Pro£essor Forest Soils and Graduate Assistant, respectively,
Soil Science Department, University o£ Florida, Gainesville, FI.
32611. The authors acknowledge the assistance of the Coopera
tive Research in Forest Fertilization (CRIFF) program for the
installation, measurements, and maintenance of the field in
stallations.
availability, they may be at the expense of long-term
site productivity (Haines et al 1975).
A series of field experiments was installed on rep
resentative soil-site types of the lower coastal plain to
determine tree response to site preparation, the in
fluence of site preparation on fertilizer effectiveness,
and whether the use of fertilizers can be substituted,
in part, for certain site preparation operations.
MATERIALS AND METHODS
Slash pine responses to three types of site prepara
tion in factorial combination with three fertilizer treat
ments were measured at seven lower coastal plain sites
for 8 years after planting. Four replications of 27 x
30 m plots in a 3 x 3 factorial experiment, where site
preparation treatments formed whole-plots and fertil
ization treatments comprised sub-plots, were installed
at each site.
The site preparation (whole-plot) treatments were
(a) chopa minimum preparation consisting of slash
burning and a single pass with a drum chopper, (b)
disksingle disking in addition to a prior burn and
chop, and (c) bedstandard ridging with a disk harrow
following burning and chopping.
The fertilizer (sub-plot) treatments consisted of (a)
noneno nutrients added, (b) CSP45 kg P/ha ap
plied as concentrated superphosphate, and (c) DAP-
40 kg N plus 45 kg P/ha applied as diammonium phos
phate. Fertilizer materials were broadcast-applied over
the entire plot surface within 2 to 3 months after plant
ing 1-0 seedlings. Nine-meter wide 3 rows) buffer
strips were left on all sides of the 21 x 24 m net sub
plots.
Tree-height measurements were made at 3, 5, and
8 years after treatment (except that not all tests were
measured at 8 years). Tree-survival percentage was
calculated at 3 years after planting and percentages of
trees damaged by disease (stem canker) were deter
mined at each measurement period.
Soils were initially surveyed to ensure that each
replication blocked a homogenous soil type, but there
was no requirement that all blocks at each site be
established on the same soil type. Therefore, two or
more soil series were often present at a given test site.
In order to gain a better understanding of the effects
of soil properties on responses, blocks containing sim
ilar soils across all test sites were grouped on the basis
of those profile and drainage characteristics thought
to influence tree response to site preparation and fertil
ization. Twenty-three of the more uniform blocks were
selected for this study and combined into four soil
groups for statistical analyses and discussion, as shown
in Table 1. Group A soils were Aquults, group B con
sisted of poorly to very poorly drained sands and they
varied from Grossarenic Paleudults to Typic Huma-
quepts, group C soils were Ultic Haplaquods, and
group D soils were Aerie Haplaquods. Some chemical
properties of the principal horizons of the four groups
of soils are summarized in Table 2, for samples col
lected prior to treatment.


Soil and Crop Science Society of Florida
52
TABLE
1.Soil groups for site preparation
TERPRETATIONS.
FERTILIZATION IN-
Soil
Representative
soil series
Diagnostic Characteristics
group
Drainage class
B horizon
A (3)t
Portsmouth
Bladen types
Very poorly to
somewhat poorly
Argillic within
50 cm of surface
B (6)
Rutlege
Plummer types
Very poorly to
somewhat poorly
No spodic, argil
lic deeper than
50 cm
C (9)
Mascotte
Sapelo types
Poorly to some
what poorly
Spodic underlain
by argillic
D (5)
Ridgeland
Leon types
Poorly to mod
erately well
Spodic with no
underlying
argillic
+( ) indicates number of replications in each soil group.
TABLE 2.Mean soil chemical concentrations in principal
soil horizons by soil group in pre-treatment samples.
Total Double-acid extractable
Horizon
(H,0) OM N
P K Ca Mg
Fe
Al
7n
Soil group A (Shallow
argillic horizon)
Ai
4.49 4.12 0.102
1.3 23 63
31
147
271
A2t
4.42
0.6 8 75
33
67
259
Ct
4.73
0.3 17 12
70
38
253
Soil group B (Deep argillic horizon)
A1
4.92 3.97 0.077
0.6 19 75
12
59
322
A3
4.94
2.4 4 24
7
14
298
Ct
5.06
0.7 5 3
16
15
174
Soil group C (Spodic above argillic horizon)
A1
4.30 3.38 0.067
2.6 15 121
32
15
110
Bh
4.62
3.8 5 34
6
28
497
Ct
4.80
4.4 4 3
11
40
252
Soil group D (Spodic with
no argillic horizon)
A1
4.43 3.22 0.051
3.4 25 102
35
12
66
Bh
4.65
2.3 5 21
7
15
537
c
4.84
3.6 4 2
7
35
489
Soils were sampled from selected combinations of
site preparation-fertilization treatments 6 years after
planting. The control and the four combinations which
produced the greatest tree-height growth response at
age 5 years were sampled by horizons at six random
points in tree rows. Combinations of treatments sam
pled included (a) chopnone, (b) diskDAP, (c) bed
none, (cl) bedCSP, and (e) bedDAP. Samples were
analyzed for pH (1:2 soil-water suspension), organic
mater content (Walkley-Black), and double-acid (0.05N
HC1-0.025N HSO.,) extractable nutrients.
Foliage was collected from six dominant or codom
inant trees in plots from which soils were sampled.
Samples were preserved on ice until they could be
oven-dried at 65C. Total N was determined by the
macro-Kjeldahl procedure and K, Ca, Mg, Fe, and A1
were analyzed by atomic absorption techniques, after
ashing at 450 C. Phosphorus was determined colori-
metrically in ascorbic acid and molybdate-sulfuric acid
solutions (Jackson, 1958).
The effects of site preparation on soil bulk density
of the surface and B horizons were determined at three
test sites 6 years after treatment. Soils were sampled
witli a hammer-driven core sampler (Blake, 1965), after
excavating to within 2 cm of selected depth with a soil
auger.
The total biomass of understory vegetation was
measured at one test location 6 years after treatment.
For this purpose, five rectangular plots were randomly
established within each of the five selected treatments
of three blocks. Rectangular plots were 0.4 m wide and
extended from the base of a pine tree to a midpoint
between rows. All above-ground green biomass was
clipped, bagged, and dried to constant moisture at
60 C.
Tree growth data were statistically examined by
analysis of variance techniques for factorial experi
ments with unequal replications. Main effects for site
preparation and fertilizer treatments were obtained
for the study as a whole and by individual soil groups.
A stepwise multiple regression was used to regress
mean height and height increment against soil and
foliage chemical properties.
RESULTS AND DISCUSSION
Tree Growth Responses
Site preparation and fertilization treatments signif
icantly increased slash pine height growth when data
for all locations were combined. However, the mag
nitude and duration of the treatment responses de
pended on soil properties and data are discussed by soil
groups as described in Table 1.
Soil Group A (Shallow argillic B horizon): Slash
pine on these Aquults responded dramatically to both
site preparation and fertilization (Table 3), similar to
earlier results for wet savanna soils (Pritchett and
Smith, 1974). Trees on the minimally-prepared (chop)
treatment grew very poorly, averaging only 1.02 m
after 5 years. The main effect of site preparation on
tree growth was highly significant, and bedding re
sulted in better growth than either chop or disk treat
ments (Fig. la). Disking increased tree heights over
heights of trees in minimally-prepared plots an average
of 29% after 5 years, although this increase was not
statistically significant due to excessive between-plot
variation. On the other hand, trees in bedded plots
were almost twice as tall as trees in the minimally-
prepared plots when averaged across all fertilizer treat
ments, giving a highly significant response.
Bedding improved aeration in the rooting zone
during the first year after planting in these Aquult
soils. It may have improved nutrition of the young
trees by concentrating surface soil organic matter into
mounds where tree roots were largely confined during
the early years of stand establishment (Haines and
Pritchett, 1965) and by hastening organic matter de
composition and mineralization. Soil samples taken 6
years after treatment failed to indicate any significant
difference in concentrations of organic matter, total N,
or extractable P between the minimum treatment and
bedded plots in the absence of fertilizers. Tabular data
are not presented herein, in the interest of space, but
surface soil (A1 horizon) total N averaged 1.01 and
1.13%, and extractable P averaged 1.2 and 1.3 ppm in
the chopped and bedded plots, respectively.


53
Proceedings, Volume 39, 1980
Soil group A Soil group B
DAP CSP None
Soil group C
Soil group D
Fig. 1.Mean heights of 5-year-old slash pines in soils groups
A (Aquults), B (Grossarenic Paleudults to Typic Humaquepts),
C (Ultic Haplaquods), and D (Aerie Haplaquods) that received
three site preparation and three fertilization treatments in fac
torial combination.
The highly significant main effects of fertilizers on
tree heights at the end of 5 years are shown in Fig. la.
Height responses to CSP fertilizer amounted to a 91%
increase over the non-fertilized plots, while the re
sponse to DAP averaged 116% compared to non-
fertilized plots, when averaged across all site prepara
tion treatments. It is interesting to note that the cur
rent height increment during the fifth year amounted
to 123 and 132% more than the non-fertilized plots
for the CSP and DAP treatments, respectively (Table
3). This indicated that the magnitude of the response
to P fertilizers was still increasing. These large re
sponses were a consequence of the extremely low avail
able P in non-fertilized soils (only 1.3 ppm extractable
P). While the absolute increase in heights due to fer
tilization was greater on bedded plots than on disked
plots (2.02 vs. 1.72 m), the percent increase in height
TABLE 3.Mean annual height growth in the fifth year by
TREATMENT COMBINATIONS AND SOIL GROUPS.
Treatment
A (3)f
Soil group
B (6) C (9)
D (5)
Site
preparation
Fertilization
cm
Chop
none
24
48
68
58
Chop
CSP*
77
56
82
67
Chop
DAP*
85
58
85
60
Disk
none
38
57
82
68
Disk
CSP
97
64
87
77
Disk
DAP
101
63
94
83
Bed
none
72
63
94
78
Bed
CSP
125
66
93
74
Bed
DAP
114
64
101
81
CSP = concentrated superphosphate and DAP = diam-
monium phosphate, each applied at rate of 45 kg P/ha.
t( ) indicates number of replications in each soil group.
of fertilized trees over non-fertilized trees was greater
in disked plots than in bedded plots (122 vs. 78%),
because of the generally better growth on the latter
plots. In spite of these apparent differences, the inter
action between site preparation and fertilization was
statistically non-significant, indicating that the re
sponses to the two types of treatments were additive
and that one cannot effectively substitute for the other
on these Aquults (Fig. la).
Soil Group B (Argillic horizon deeper than 50 cm):
Site preparation and P fertilization significantly in
creased tree height growth on group B soils. The main
effects of site preparation were generally greater than
those associated with P fertilizers, after 5 years (Fig,
lb). Tree heights on plots that were prepared by disk
ing and bedding averaged 32 and 46%, respectively,
greater than heights of trees in minimally prepared
plots. On the other hand, the application of CSP and
DAP fertilizers resulted in increases in tree growth of
12 and 19% respectively, over the non-fertilized trees
averaged across all site preparation treatments.
Because these poorly drained soils were quite de
ficient in available P, averaging less than 1 ppm of ex
tractable P in the A1 horizon (Table 2), it is surprising
that the early height response to P fertilizers was not
considerably greater than shown in Fig. lb. Further
more, annual height increment in the fifth year indi
cated a slight reduction in the rate of response to P, as
compared to that for the first 3 years. For example,
trees treated with CSP averaged 7 cm more annual
growth than non-fertilized trees during the first 3 years,
but they averaged only 6 cm more annual growth dur
ing the fourth and fifth years. This decrease in growth
advantage due to fertilizers may have resulted from a
gradual lowering of the water table in these wet soils,
generating a greater volume of soil for tree roots to
exploit for nutrients (Pritchett and Smith, 1972). The
magnitude of height response (main effect) to bedding
also decreased from an average of 23 cm per year dur
ing the first 3 years to 10 cm in the fifth year.
There were no significant interactions between site
preparation and fertilization treatments in this soil
group, although there was a trend toward greater re
sponse to fertilizers on the minimally prepared plots.
Soil Group C (Spodic above an argillic horizon):
The main effects of height growth responses to disking,
bedding, and P fertilization on these Ultic Haplaquods
were generally significant. The responses to bedding
varied from 0 to almost 2 m, after 5 years, and was
greatest on the most poorly drained soils of the group.
Tree heights on minimally prepared plots averaged
2.44 m compared to 3.59 m on bedded plots. The mag
nitude of the annual growth response associated with
bedding was almost the same at 5 as at 3 years, but
after 8 years the growth increases had mostly dis
appeared, indicating that the initial gains due to bed
ding were rapidly diminishing, even though trees on
bedded plots were still almost 1 m taller than those on
minimally prepared plots (Fig lc).
Average heights of trees on non-fertilized, CSP, and
DAP-treated plots were 2.61, 2.95, and 3.36 m, respec
tively, after 5 years. After 8 years, the difference in
heights between fertilized and non-fertilized trees had
increased slightly. Nitrogen (as DAP) appeared to give
an additional growth response above that obtained
from P fertilizer alone. The response of young slash


54
Soil and Crop Science Society of Florida
pine to N fertilizers applied to flatwoods soils was
previously reported (Pritchett and Smith, 1972).
Responses to DAP were somewhat larger in min
imally prepared plots than in bedded plots. For ex
ample, the increases over the non-fertilized plots av
eraged 0.85, 0.72, and 0.51 m in the chop, disk, and
bed plots, respectively. These Ultic Haplaquods were
the only soils on which it appeared that NP fertilizers
might substitute, at least in part, for intensive site
preparation.
Soil Group D (Spodic without argillic horizon):
Slash pine grown on these Typic Haplaquods re
sponded well to site preparation in the early years of
plantation establishment. Trees on bedded plots after
5 years were significantly taller than those on disked
plots (Fig. Id). However, there were no differences in
annual growth rates among the three site preparation
treatments after 8 years.
Fertilizer, particularly DAP, produced significant
growth responses during the first 3 years, but by the
fifth year annual height growth was essentially the
same for all fertilizer treatments (Table 3).
Other Responses to Treatments
The main effects of site preparation and fertiliza
tion on soil bulk density, seedling survival, foliar nutri
ent concentrations, fusiform rust incidence, and under
story biomass were determined 6 years after trees were
planted (except survival was also determined after 3
years). Most treatment effects were not significant at
this stage of stand establishment and tabular data have
not been included, in the interest of space. However,
they are available in a thesis (Flaig, E. G. 1979. Some
soil and site properties influencing the response of
slash pine to site preparation and fertilization. M.S.
Thesis, University of Florida, Gainesville), and some
trends are summarized in this section.
Surface soil (0-20 cm) bulk densities averaged 1.33,
1.25, and 1.15 g/cm3 in the chopped, disked, and
bedded plots, for the three soils tested (one Ultic and
two Typic Haplaquods). In only one Typic Haplaquocl
were differences in bulk density between the chopped
plots (1.41 g/cm3) and bedded plot (1.08 g/cm3) sta
tistically significant, after 6 years.
The percentages of planted trees surviving after 3
years were generally high and varied more among soil
groups than among treatments. Survival in soil groups
A and B tended to be better than in the Spodosols
(groups C and D), but since seedling origin, soil mois
ture conditions at time of planting, and skill and care
of the operator differed among locations, generaliza
tions are probably not meaningful. The average (main)
effects on survival of site preparations, across all soils,
were 82, 86, and 89% for chopping, disking, and bed
ding, respectively. Differences in survival associated
with P fertilizer treatments were all small and non
significant.
Most nutrient concentrations in current-year need
les differed significantly among soil groups, but, except
for P and Al, they were not significantly influenced by
treatment. For example, mean levels of N were 0.92,
0.84, 0.78, and 0.79% in tissue from group A, B, C, and
D, respectively. Concentrations of K were also higher
in the wetter soils (A and B) than in the flatwoocl soils
(C and D), but the reverse was true for P and Ca. Phos
phorus was higher in tissue from fertilized plots, as
expected, but it was not expected that Al would also
be higher in tissue from P fertilized trees than in non-
fertilized trees. For example, Al in non-fertilized and
fertilized tissues from group A plots averaged 288 and
447 ppm, while those from group B plots averaged 338
and 384 ppm. Aluminum concentrations in tissue from
group C soils averaged 398 and 438 ppm and from
group D soils, 362 and 371 ppm, respectively, for non-
fertilized and fertilized plots.
Fusiform rust incidence varied from 1 to 7% of in
fected stems at some locations to 13 to 27% at other
locations, although the correlation with soil group was
not significant. This was probably due to the great
variation in infection rate within soil groups. The
main effects of fertilization were not significant, but
the effects of the more intense preparation treatments
were significantly greater (p = 0.05) than the chop
treatment, with average values of 5.7, 9.6, and 9.3%
for chop, disk, and bed.
Total understory biomass was not significantly
affected by site preparation or fertilization, after 6
years. Apparently any early reduction in ground cover
competition as a result of site preparation had largely
disappeared by that time.
MANAGEMENT IMPLICATIONS
Site preparation by flat disking improved tree
growth over that obtained on the burn and chop plots,
on these very poorly to imperfectly drained sites. This
response apparently resulted primarily from the reduc
tion in competition from understory vegetation. Bed
ding resulted in even greater response in growth than
disking (1 to 2 m advantage after 5 years). Since the
response to bedding was greatest on group A soils
(Aquults), it is presumed that tree growth improve
ment from bedding resulted, in large part, from better
aeration in the root zone, although an increase in the
rate of N and P mineralization from organic matter
may also be a factor. It is not known at this stage of
stand development whether early growth responses to
site preparation will persist to rotation age. There are
indications that they may not, particularly on group
C and D soils. It also appears that these treatments
will have no long-term effects on bulk density or chem
ical composition of sandy soils.
The responses to CSP and DAP fertilizers were
greatest on the wet sites, particularly group A soils,
and the response did not diminish during the first 5 to
8 years. The small quantity of N applied in DAP (40
kg N/ha) resulted in a greater response than that ob
tained from P alone. The responses to fertilizers and
site preparation were generally additive, so that one
operation can not effectively be substituted for the
other, with the exception of the Ultic Haplaquods.
LITERATURE CITED
Blake, G. R. 1965. Bulk density, p. 374-390. In C. A. Black (ed.)
Method of Soil Analysis. Pt. I. Agronomy 9. Am. Soc. Agron.,
Madison, WI.
Haines, L. W., and W. L. Pritchett. 1965. The effects of site
preparation on the availability of soil nutrients and slash
pine growth. Soil Crop Sci. Soc. Florida Proc. 25:356-364.
Haines, L. W., T. E. Maki, and S. G. Sanderford. 1975. The
effects of mechanical site preparation treatments on soil
productivity and tree (Pinus taeda L. and P. elliotlii Engelm.
var elliottii) growth, p. 379-395. In B. Bernier and C. H.
Winget (ed.) Forest Soils and Forest Land Management. Laval


55
Proceedings, Volume 39, 1980
Univ. Press, Quebec.
Jackson, M. L. 1958. Soil Chemical Analysis. Prentice-Hall, Inc.,
Englewood Cliffs, N.J. 598 p.
Pritchett, W. L., and W. H. Smith. 1972. Fertilizer responses in
young pine plantations. Soil Sci. Soc. Am. Proc. 36:660-663.
Pritchett, W. L., and W. H. Smith. 1974. Management of wet
savanna soils for pine production. Florida Agr. Expt. Sta.
Bull. 762. 22 p.
Corn Response to Nitrogen and Phosphorus in a
Florida Ultisol for Simulation of Field Fertilization
Techniques Used in El Salvador1
E. Jacome and W. G. Blue2
ABSTRACT
The current fertilization technique for corn (Zea
mays L.) in El Salvador, Central America, is to apply
N at 50 kg/ha as (NH4)2S04 and P at 44 kg/ha (100
kg P205/ha) as triple superphosjriiate (TSP) under the
seed in a planting trench, with seed and fertilizer sep
arated by 2 to 3 cm of soil. Corn grain yields are rela
tively low and grain production per unit of N is ap-
proximately 11 kg/kg of applied N in contrast to more
than 30 kg of grain/kg of applied N in other areas.
Dothan fine sandy loam (fine, loamy, siliceous,
thermic Plinthic Paleudult) was used in a greenhouse
pot experiment to study the effect of banded applica
tions of N as (NH4),S04 and P as TSP under the corn
plant on its top growth, root development, and nutri
ent iqitake. The soil was limed 3 weeks before initia
tion of the experiment. Where fertilizer was applied in
a band, the band was 5 cm wide and 2 to 3 cm below
the seed. Treatments which did not receive (NH4),S04
in the band received the same amount of N as
(NH4),S04 in solution applied to the soil surface; all
treatments received K as K2S04 also applied in solution
to the soil surface. Seed germination was not affected
by application of (NH4)2S04 in combination with TSP
below the seed, but plant height, herbage weight, root
weight, and nutrient contents were less than with TSP
alone below the seed. Oven-clry herbage and root
weights 33 days after planting were reduced by 50 and
40%, respectively, by the (NH4),S04; plant height
was also reduced by 15%. This adverse effect of
(NH4)2S04 applied below the seed under nearly ideal
moisture conditions in this greenhouse experiment
could be amplified under field conditions of uncertain
rainfall. Furthermore, the magnitude of corn grain
yields in most cases under field conditions in El
Salvador would indicate that N could be omitted at
planting and applied as side dressings at appropriate
times, thus avoiding the potential for damage to young
corn.
Additional Index Words: Ammonium sulfate,
Triple superphosphate, Banded fertilizer, Zea mays L.
Corn (Zea mays L.) constitutes more than 50% of
the basic human diet in all Central American
countries; it is produced primarily by small farmers
iFlorida Agricultural Experiment Stations Journal Series No.
2280.
^Graduate student and Professor (Soil Chemistry and Fertil
ity), Soil Science Department, Institute of Food and Agricultural
Sciences, University of Florida, Gainesville, FL 32611.
(campesinos) (U. S. Economic Research Service, 1963,
1977 and Salazar, 1968). The development of technical
programs to improve existing agronomic practices,
which have been used by farmers for generations, is
common. The current production system in El Salva
dor involves preparation of land by animal traction
and the Egyptian plow (a wooden plow with metal
point). Planting trendies which are approximately 20
cm wide at the top, 5 cm wide at the bottom, and 10
to 15 cm deep are made at 80-cm intervals, also with
the Egyptian plow. If fertilizers are used, they are
applied by hand in a band at the bottom of the trench.
The fertilizer is covered by kicking a 2 to 3 cm thick
layer of soil over it. Corn seeds are placed on the soil
immediately above the fertilizer and covered with addi
tional soil. Fertilizer materials are usually (NH4)2S04
and triple superphosphate (TSP). Ammonium sulfate
is widely used because most El Salvadorean soils are
considered to be S deficient. Potassium is presently in
adequate supply in most soils, and soil pH is usually
above 5.5. Almost all corn is grown without irrigation.
Several fertilizer experiments were conducted through
out El Salvador from 1959 through 1968 (Salazar,
1968). Phosphorus at rates from 0 to 70 kg/ha (0 to
160 kg of P2Os/ha) was applied below the seed in the
previously described manner. Nitrogen was applied at
rates from 0 to 180 kg/ha. In some experiments, all of
the N was applied in the trench before planting and in
others some N was applied in the trench and some
applied as side-dressings beside the row. However, in
all experiments, treatments which included N had a
substantial amount applied below the seed.
Corn grain yields in this series of experiments were
generally low and response to N was usually in the
order of 11 kg of grain/kg of N applied. This is in
contrast to corn grain production/kg of N of 33 in
Ohio (Agronomy Dept., Ohio State Univ., 1978), and
31 to more than 40 in Florida (Rhoads and Stanley,
1979; Robertson et al., 1968).
Current experiments in El Salvador continue to
give responses similar to those reported by Salazar,
1968. The current recommendation is to apply 50 kg
of N/ha as (NH4),S04 and 44 kg of P/ha (100 kg of
P205/ha) as TSP in the trench below the seed. It has
long been known that relatively low P rates in P-
deficient soils may be more effective when the P is
placed in a band beside the seed (Nelson, 1956; Singh
and Black, 1964; and Welch et al., 1966) than when
broadcast and incorporated. However, it has also been
recognized that N in sizeable quantity placed near the
seed may be harmful because of high salt concentration
(Tisdale and Nelson, 1975). We believe the technique


56
Soil and Crop Science Society of Florida
of fertilizer placement used in El Salvador may be at
least partially responsible for low response to fertilizer
N and P.
The objective of this experiment was to compare
the growth response of corn to a fertilizer-placement
treatment similar to that used in El Salvador with
treatments where P only is applied in a band below
the seed and incorporated into the soil.
MATERIALS AND METHODS
The experiment was conducted in the greenhouse
in Gainesville, Florida, from 23 May to 27 June 1979.
The upper 15 cm of a Dothan fine sandy loam (fine,
loamy, siliceous, thermic Plinthic Paleudult) soil from
Escambia County, Florida, was used. The original soil
pH in a soihwater suspension of 1:2 was 4.1, electrical
conductivity (EC) was 1.15 mmho/cm, CEC was 8.36
meq/100 g, and ECEC was 3.04 meq/100 g. The clay
and silt contents of this soil were 8.2 and 36.7%, re
spectively, on a weight basis; mineralogy of the clay
fraction was a mixture of kaolinite, quartz intergrades,
and feldspars.
The soil was limed with 2 meq of CaCO3/100 g and
fertilized with a micronutrient frit at 15 p,g/g 3 weeks
before use in the experiment. After incubation and
drying, 2 kg of soil were placed above 650 g of small
stones in tapered plastic pots which were 15 cm wide
at the top and 15 cm high. Fertilizers were applied as
shown in Table 1. Treatment 4 represented the com
mon fertilization practice in El Salvador. In El
Salvador, corn is planted in 80-cm rows; this gives
12,500 m of row/ha. It is currently recommended that
(NH4)2S04 and TSP be banded beneath the seed at
rates of 50 kg of N and 44 kg of P/ha (100 kg of
P205/ha). Fertilizer materials are applied in a band
approximately 5 cm wide, so that they are equivalent
to 1 g of (NH4)2S04 and 0.9 g of TSP per 5 cm of row.
The amount of fertilizer applied per pot was based on
the previously described relationships and 15-cm diam
eter of the pots. In those treatments which received the
same amount of nutrient incorporated, soil and fertil
izers were mixed thoroughly in plastic bags before
placement in pots.
All pots received a uniform application of K,S04
in solution, at a rate of 200 pg/g of soil. Treatments
1, 2, and 3 received (NH4)2S4 in solution at a rate of
300 pg/g based on soil weight; this was the same quan
tity of N that was applied to Treatment 4. Both K2S04
TABLE 1.Fertilization materials and techinques on a Florida
Ultisol for simulation of field treatments used in El Salva
dor.
Treatmentsf
Fertilizer nutrients
N
p
N
(nh4)2so4
P25
TSP
kg/ha
g/5 cm row
kg/ha
g/5 cm row
1
50
0
0
0
2
50
0
100
0.9
3
50
0
100
Incorporated
4
50
1
100
0.9
(Treatments 1 through 3 received N as (NH4)2S04 in solution
equivalent to that applied to Treatment 4. All treatments received
K as KS04 equivalent to 200 pg/g of soil.
and (NH4),S04 were applied to the soil surface in two
applications, one half at emergence of seedlings and
one half 10 days after emergence.
Corn (variety Dekalb XL-395) was used in the ex
periment; germination observations, plant growth
measurements, and chemical determination of nutri
ents in plant tissue were made. Soil samples were ob
tained by inserting a tube through the fertilizer band
which corresponded to the plant row.
A randomized block design with four replications
was used. The data were analyzed statistically by
analyses of variance; treatment means were compared
by Duncans new multiple range test.
RESULTS AND DISCUSSION
Corn seed germination was not significantly re
duced by any of the treatments (Table 2). Plant heights
at 9, 14, and 33 days after emergence were adversely
affected by (NH4)2SO, under the seed in addition to
the P (Treatment 4). At 33 days, plant height from
Treatment 1 was severely depressed by P deficiency
and plant height from Treatment 4 remained signif
icantly less than from Treatments 2 and 3 with P only
banded under the seed or with P incorporated. Corn
herbage weights 33 days after germination were dras
tically affected by treatments; herbage weight from
Treatment 1 without P was only 1.0 g/pot and from
Treatment 4 with N and P applied under the seed
11.9 g/pot compared with 19.5 g/pot from Treatment
2 with P alone under the seed. Plant height of Treat
ment 4 at the same age was 102 cm, 15% less than 121
and 117 cm for Treatments 2 and 3. Plant root systems
were affected in a manner similar to herbage. The
root system from Treatment 1 without P was only 0.2
g/pot; that from Treatment 4 with N and P under the
seed was 1.9 g/pot while that from Treatment 2 with
P only under the seed was 4.3 g/pot (Table 2). The
smaller root system from Treatment 4 was undoubtedly
a consequence of the high salt concentration immedi
ately below the plants in the early growth stage. It is
likely that this restriction of root growth in young
plants may result in a more shallow, less developed
root system which will restrict water and nutrient up
take from subsoils.
Robertson and Hutton (1959) and Mengel and
Barber (1974) held that the deeper the root system, the
better the plant is able to withstand periods of mois
ture stress. Root system development is particularly
important in the Central American countries, where
most producers depend only on rainfall; a well de
veloped root system is essential to explore deeper parts
TABLE 2.Corn growth response to fertilizer rates and place
ment on a Florida Ultisol.
Treat- Germi- Days after planting Oven-dry weights
ments
nation
9
14
33
Herbage
Roots
.. Plant height,
cm ..
g/pot
1
95a*
5 a
30 a
43 c
1.0 c
0.2 c
2
100 a
4 a
38 a
121 a
19.5 a
4.3 a
3
90 a
4 ab
33 a
117 a
18.2 a
3.8 a
4
95 a
3b
21 b
102 b
11.9 b
1.9 b
Values within
columns
followed by the
same letter
do not
differ significantly at the 0.05 level of probability according to
Duncans new multiple range test.


57
Proceedings, Volume 39, 1980
of the soil where moisture is retained if high grain
yields are to be produced.
Herbage nutrient concentrations were generally
adequate for plant growth (Table 3); except for P,
nutrient concentrations were inversely related to top
growth. Herbage concentrations of P and K from
Treatment 4 were significantly larger than from Treat
ments 2 and 3. Calcium, Mg, and Cu concentrations
were low for all treatments except 1 where growth was
poor because of P deficiency. Concentrations of Fe, Mn,
and Zn were adequate for plant growth in Treatments
2, 3, and 4; however, they were unusually high for
plants from Treatment 1. With the exception of Fe,
Cu, and Zn, nutrient contents were significantly re
duced for Treatment 4 as compared with 2 and 3
(Table 4). The only difference between Treatments 2
and 3, and 4 was the manner of N application. In
Treatment 4, N was applied prior to seeding in a band
only 2 to 3 cm below the seed; therefore, the reduction
of plant growth from Treatment 4 was likely caused by
the high concentration of (NH4)2SOf in the 5-cm wide
application band.
Root nutrient concentrations were relatively un
predictable, probably because of analytical error asso
ciated with small sample size; therefore, these data are
not presented. However, because of smaller root mass,
root nutrient contents from Treatment 4 were lower
than from Treatments 2 and 3.
Values for EC (Table 5) in the soil ranged from
5.8 to 6.4 mmho/cm for Treatments 2, 3, and 4. For
Treatment 1, EC was significantly higher probably be
cause of poor plant growth and low nutrient uptake as
a consequence of severe P deficiency. High concentra
tions of K in the soil and N in the foliage support this
statement.
Although soil pH was lower than that intended,
the appearance of plants in Treatments 2, 3, and 4
showed no evidence of A1 toxicity. Even though pH
TABLE 5.Soil pH, electrical conductivity, and double-acid
EXTRACTABLE NUTRIENTS IN SOIL AFTER FERTILIZATION AND CROPlING.
Double-acid
Treat- extractable nutrients
ments
pH
ECf
P
K
Ca
Mg
mmho/cm
ppm ...
1
4.8 a*
10.7 a
3c
193 a
261 c
180 a
2
4.1 c
6.0 b
68 b
84 b
504 ab
120 a
3
4.1 c
5.8 b
55 b
19c
428 b
166 a
4
4.3 b
6.4 b
186 a
46 c
605 a
146 a
fEC of the virgin soil was 1.2 mmho/cm.
Values within columns followed by the same letter do not
differ significantly at 0.05 level of probability according to
Duncans new multiple range test.
values were low, A1 saturation of the ECEC (Table 6)
was substantially below the 44% level mentioned by
Kamprath (1970) for normal growth of corn. Further
more, corn responded to lime in mineral soils only
when A1 saturation of the ECEC was above 70%, at
which point concentration of soil solution A1 increased
sharply (Evans and Kamprath, 1970). In Treatments 2
and 3, with large root systems, exchangeable A1 was 1.6
and 1.7 meq/100 g of soil, respectively, with percentage
saturations of the ECEC of 28 and 31. In contrast, the
root system from Treatment 4 with (NHJ),SO,1 applied
below the seed was relatively small; exchangeable A1
in soil from Treatment 4 was 0.9 meq/100 g which
represented a percentage saturation of the ECEC of
only 18. Phosphorus in the soil after cropping was
significantly higher in Treatment 4 than in soils from
Treatments 2 and 3, probably because of smaller root
and herbage nutrient contents.
We think that this adverse effect of (NH4)2S04 ap
plied below the seed under nearly ideal moisture con
ditions in this greenhouse experiment could be ampli-
TABLE 3.Corn herbage nutrient concentrations.
Oven-dry herbage nutrients
Treatments
Nf
P
K
Ca
Mg
Fe
Mn
Cu
Zn
%
1
5.03
0.09 c*
3.19 a
0.31 a
0.47 a
179 ab
151 a
8 a
228 a
2
2.95
0.21 b
1.50 c
0.15 c
0.22 b
92 b
41 b
2b
23 b
3
2.83
0.21 b
1.75 c
0.17 b
0.22 b
116 b
41 b
4b
25 b
4
3.31
0.29 a
2.50 b
0.14 d
0.21 b
209 a
39 b
3b
30 b
fNitrogen was determined in samples composited from all replications.
Values within columns followed by the same letter do not differ significantly at 0.05 level of probability according to Duncans new
multiple range test.
TABLE 4.Corn herbage nutrient contents.
Herbage nutrients
Treatments N P K Ca Mg Fe Mn Cu Zn
mg/pot
1
50
0.9 d*
31.9 d
3.1 d
4.7 d
0.2 b
0.2 d
0.008 b
0.228 b
2
573
40.6 a
290.3 b
29.6 b
43.7 a
1.8 a
0.8 a
0.046 a
0.439 a
3
515
37.4 b
315.5 a
30.1 a
39.5 b
2.1 a
0.7 b
0.067 a
0.451 a
4
394
32.9 c
279.5 c
16.1 c
16.0 c
2.6 a
0.5 c
0.035 ab
0.350 a
Values within columns followed by the same letter do not differ significantly at the 0.05 level of probability according to Duncans
new multiple range test.


58
Soil and Crop Science Society of Florida
TABLE 6.Exchangeable cations and ECEC for soil after fer
tilization AND CROPPING.
A1
Treat- Exchangeable cationsf satn-
ments
Al
H
Ca
Mg
ECEC
ration
%
1
0.7 b*
0.8 a
LI d
1.4 a
3.9 b
18
2
1.6 a
0.8 a
2.2 b
0.9 b
5.6 a
28
3
1.7 a
0.8 a
1.8 c
1.2 ab
5.4 a
31
4
0.9 b
0.6 a
2.6 a
1.1 ab
5.1 a
18
fThe values for the virgin soil were 0.57, 0.40, 1.01, 1.03, and
3.0 for exchangeable Al, H, Ca, Mg, and ECEC, respectively.
Values within columns followed by the same letter do not
differ significantly at the 0.05 level of probability according to
Duncans new multiple range test.
fied under field conditions of uncertain rainfall.
Furthermore, the magnitude of corn yield in most cases
under field conditions in El Salvador would indicate
that N could be omitted at planting and applied as
side dressings at appropriate times, thus avoiding the
potential for damage to young corn.
LITERATURE CITED
Agronomy Department, Ohio State University. 1978. Soil fertility
research report. Series No. 219. Ohio State University, Colum
bus, Ohio.
Evans, C. E., and E. J. Kamprath. 1970. Lime response as related
to percentage A1 saturation, solution Al, and organic matter
content. Soil Sci. Soc. Am. Proc. 34:893-896.
Kamprath, E. J. 1970. Exchangeable aluminum as a criterion for
liming leached mineral soils. Soil Sci. Soc. Am. Proc. 34:252-
254.
Mengel, D. B and S. A. Barber. 1974. Development and distribu
tion of the corn root system under field conditions. Agron. J.
66:342-344.
Nelson, L. B. 1956. The mineral nutrition of corn as related to
its growth and culture. Adv. Agron. 8:321-375.
Robertson, W. K., and C. E. Hutton. 1959. Fertilizer placement
studies on farm crops. Soil and Crop Sci. Soc. Florida Proc.
19:190-196.
Robertson, W. K., L. G. Thompson, Jr., and L. C. Hammond.
1968. Yield and nutrient removal by corn (Zea mays L.) for
grain as influenced by fertilizer, plant population, and hybrid.
Soil Sci. Soc. Am. Proc. 32:245-249.
Rhoads, F. M., and R. L. Stanley. 1979. Effect of population and
fertility on nutrient uptake and yield components of irrigated
corn. Soil and Crop Sci. Soc. Florida Proc. 38:78-81.
Salazar, R. J. 1968. Estudio de fertilizacin en maiz, Ministerio
de Agricultura y Ganadera. El Salvador. Boletn Tcnico No.
50.
Sanchez, P. A. 1976. Properties and management of soils in the
tropics. A. Wiley-Interscience Publication, New York, N. Y.
Singh, R. M., and C. A. Black. 1964. Test of the DeWit compen
sation function for estimating the value of different fertilizer
placement. Agron. J. 56:572-574.
Tisdale, S. L., and W. L. Nelson. 1975. Soil Fertility and Fertil
izers. 3rd Edition. MacMillan Publishing Co., Inc., New York.
U. S. Economic Research Service. 1963. El Salvador, Its agricul
ture and trade. USDA. 49:18-22.
U. S. Economic Research Service. 1977. Foreign Agricultural Eco
nomic Report. USDA. 135:12-13.
Welch, L. F., D. L. Mulvaney, L. V. Boone, G. E. McKibben,
and J. W. Pendleton. 1966. Relative efficiency of broadcast vs.
banded phosphorus for corn. Agron. J. 58:283-287.
Growth and Cadmium Uptake by Lettuce and Radish
Fertilized with Cadmium, Zinc, and Sewage Sludge1
Charles C. Hortenstine2
ABSTRACT
A complete factorial experiment with two levels of
sewage sludge (0 and 100 metric tons/ha), three levels
of Zn (0, 50, and 100 kg/ha), and three levels of Cd
(0, 2.5, and 5.0 kg/ha) mixed throughout the soil was
conducted in the greenhouse with Arredondo fine sand
(loamy, siliceous, hyperthermic Grossarenic Paleudalf).
Indicator plant species were leaf lettuce (Lactuca sativa
L. var. crispa cultivar Grand Rapids) harvested at 8
weeks from planting followed by radish (Raphanus
sativus L. cultivar Red Globe) harvested at 6 weeks
from planting. Yields of lettuce were significantly in
creased by the sludge, but significantly decreased by
the highest rate of Zn and Cd. Water-soaked spots
which gradually coalesced with time to produce dead
tissue were prevalent on lettuce leaves in the highest
rate of Zn on soil with no sludge. These spots were
symptoms of Zn phytotoxicity which were not mani
fested in sludge treated soil. In contrast to lettuce,
yields of radish tops and roots were significantly less in
sludge treated soil as compared to soil which had re
1 Florida Agricultural Experiment Stations Journal Series No.
2281.
2Professor of Soil Chemistry, Soil Science Department, Uni
versity of Florida, Gainesville, FL 32611.
ceived no sludge. No visible symptoms of phytotoxicity
were produced in radish plants by any treatment.
Additional Index Words: Grossarenic Paleudalf,
Phytotoxicity, Lactuca sativa, Raphanus sativus.
The utilization of municipal sewage sludge (SS) as
a soil amendment or source of plant nutrients has in
creased substantially during the past several years in
the United States. Potential hazards exist when SS
containing relatively high levels of heavy metals is
applied to agricultural soils with subsequent entry of
these metals into the human food chain. Cadmium is
especially important in this respect as it can accumu
late within various body organs in amounts that can
produce disease or fatalities (Shroeder, 1965; Axelsson
and Pascator, 1966; Carroll, 1966). The incidence of
itai-itai disease in the Jintsu basin of Japan during
the 1960s focused worldwide attention on the accumu
lative effects of Cd in the diet (Tsuchiya, 1969). Jap
anese health officials (Yamegata and Shigematsu, 1970)
determined that rice was the major dietary source of
Cd in that epidemic and that the locally produced rice
contained over 1.0 ¡xg Cd/g with a range up to 3.4 p,g
Cd/g. They further stated that a daily intake of 300 ¡xg


59
Proceedings, Volume 39, 1980
Cd/person was the maximum acceptable and that 0.4
¡j.g Cd/g was the upper limit in unhulled rice.
Sludge applications to soils used for the production
of human foods are controlled to a large extent by
guidelines as set forth by the USEPA, Solid Wastes
Disposal Facilities (1978). Among the criteria proposed
by EPA are that soil pEl be at or above 6.5, total
amounts of Cd added not exceed 10 g Cd/g soil, and
that SS containing in excess of 20 mg Cd/kg would not
be permitted where certain crops are grown, i.e., leafy
vegetables that absorb relatively large amounts of Cd.
Several soil factors are known to affect Cd availabil
ity for plant uptake; among these are Zn and organic
matter (Haghiri, 1974; Maclean, 1976). The objectives
of this study were to evaluate the main effects and
interactions of Cd, Zn, and SS with a low Cd content
on the growth and Cd uptake of leaf lettuce (Lactuca
sativa L var. crispa cultivar Grand Rapids) and radish
(Raphanus sativus L. cultivar Red Globe) in Ar
redondo fine sand (loamy, siliceous, hyperthermic
Grossarenic Paleudalf).
MATERIALS AND METHODS
Arredondo fine sand, obtained from the 0 to 15-cm
depth of an uncultivated area, was air-dried and seived
to remove plant debris and small rocks. The soil was
limed with reagent grade CaC03 to pH 6.5, from an
original pH 5.9, and weighed at 2,700 g soil/pot into
plastic pots lined with polyethylene bags. The experi
mental design was a 2 x 3 x 3 factorial with two levels
of SS (0 and 100 tons/ha), three levels of Cd as CclCl2
(0, 2.5, and 5.0 kg/ha), and three levels of Zn as ZnS04
(0, 50, and fOO kg/ha) replicated four times. In addi
tion, Ca(N03)2, KH2P04, KC1, MgNOs, MnS04,
CuS04 and H3B03 reagent grade compounds were
added to each pot in sufficient amounts to assure op
timum plant growth. All plant nutrients and soil
amendments were mixed with the soil from individual
pots in a twin-shell blender. The pots were arranged on
greenhouse benches in randomized blocks and allowed
to incubate for 2 weeks before planting day. Ten
lettuce seeds were planted, and the seedlings were later
thinned to three in each pot. Soil moisture was main
tained with distilled water at about 10% by weighing
the pots at 2 to 3-day intervals. After 8 weeks from
planting, the lettuce roots and tops were removed,
washed in distilled water, dried at 70 C, weighed, and
ground in a stainless steel Wiley mill before chemical
analyses. The same amounts of N-P-K were added to
each pot as for the lettuce and 10 radish seeds were
planted. Radish seedlings were thinned to six per pot
and harvested at 6 weeks from planting date. Radish
tops and roots were prepared for analyses the same as
for the lettuce plants.
Plant tissue was ashed at 450 C for 8 hours, dis
solved in 6N HC1, made to volume with distilled,
deionized water, and analyzed by atomic absorption for
Cd. Soil samples were removed from the pots after the
radish harvest, and extracted in 0.005M diethylene-
pentaacetic acid + 0.1M triethyleneamine (DTPA) ac
cording to the method proposed by Lindsay (1972),
and analyzed by atomic absorption for Cd. Total solu
ble salts (TSS) were estimated by electrical conductance
(EC) in a saturated soil extract (USDA Handbook No.
60, 1954).
RESULTS AND DISCUSSION
Lettuce
Seed germination and seedling growth were normal
in all pots in spite of relatively high TSS in some of
the SS treated pots (discussed under Soil section).
During the second and third weeks of growth, all of
the lettuce plants in pots that had received 100 kg
Zn/ha and no SS began to develop small, water-soaked
spots which grew in size with time until a large part
of the leaves was affected. These areas gradually dried
and the affected tissue died. During the latter part of
the growth period (4 to 5 weeks), lettuce in the 50 kg
Zn/ha pots began to show the same phytotoxic effects.
This phytotoxicity was no doubt caused by the added
Zn which was, in some way, rendered non-toxic by the
addition of SS to the soil. Lettuce in SS treated pots
was also greener and appeared to be in much better
physical condition than lettuce in the pots with no SS.
Lettuce leaf yields (Table 1) increased with SS and
decreased with Cd additions to pots with no SS. The
severe phytotoxic effects produced by Zn when no SS
was added had no significant affect on yield. There
were significant SS x Cd and Cd x Zn interactions. The
yields of lettuce roots were comparable in magnitude to
the tops and are not presented.
Cadmium uptake by the lettuce leaves (Table 2)
was drastically increased by Cd additions to the soil,
but this increase was ameliorated considerably by the
addition of SS. The interactions displayed in Table 2
are quite interesting. Zinc applied to the no SS treat
ments apparently decreased Cd uptake, but increased
Cd uptake for SS-treated soil. Since lettuce leaves are
not a major item in human diets, Cd uptake of the
magnitude shown in this study should not be viewed
as a health hazard.
The Cd contents of lettuce roots (Table 3) were
increased significantly by Cd additions to the soil, but
the increases were not of the magnitude as shown by
the lettuce leaves. Sludge and Zn additions had no
effect on Cd uptake by the roots. However, there was a
SS x Zn interaction manifested by a decrease in Cd
uptake with Zn applied to no SS pots and an increase
in Cd uptake where Zn was applied to SS pots.
TABLE 1.Influence of Cd, SS, and Zn on dry matter yield of
LETTUCE.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
O
O
(
Avg
0
0
2.0
2.0
1.7
1.9
2.5
0
1.3
1.4
1.0
1.2
5.0
0
1.0
1.8
1.4
1.4
Avg
1.4
1.7
1.4
1.5
0
100
2.3
1.5
1.4
1.5
2.5
100
2.2
2.3
1.6
1.5
5.0
100
2.1
1.8
I.G
1.9
Avg
2.2
1.9
1.7
2.0
Significant differences:
P < 0.001-SS, SS x Cd.
P < 0.01Cd, Cd x Zn.


60 Soil and CRor Science Society of Florida
TABLE 2.Cadmium contents of lettuce tops crown in ar- TABLE 4.Influence of Cd, Zn, and SS on dry matter yield of
REDONDO FINE SAND. RADISH TOPS.
Cd added SS added Zn added, kg/ha
kg/ha tons/ha 0 50 100 Avg
0
2.5
5.0
0
0
0
2.3
54.7
82.7
1.1
32.3
57.7
1.6
31.8
47.4
1.7
39.6
62.6
Avg
46.7
30.4
26.9
34.7
0
100
2.3
5.6
5.7
4.5
2.5
100
18.6
18.9
33.6
23.7
5.0
100
37.1
50.8
47.5
45.1
Avg
19.3
25.1
28.9
24.4
Significant differences:
P < 0.001Cd, SS, SS x Cd, Cd x Zn, SS x Cd x Zn.
Radish
Radish top weights were decreased by the addition
of SS to the soil (Table 4) and there was a SS x Zn
interaction. Germination and plant growth were
normal in all pots and there were no symptoms of
phytotoxicity produced in any of the radish plants. It
is noteworthy that SS caused about a 25% decrease in
radish top weights, whereas it caused an increase of
about the same amount in lettuce weights.
Cadmium contents of radish tops (Table 5) were
increased by Cd additions and decreased by Zn addi
tions to the no SS treatments. All interactions tested
were significant except for the SS x Cd interaction.
Cadmium uptake by the radish tops was not as great
as in the lettuce leaves (20 vs 30 fig/g overall averages),
but this may have resulted from the longer growing
period for lettuce (8 vs 6 weeks). However, Turner
(1973) found differences of the same magnitude be
tween lettuce (24 fig Cd/g) and radish tops (15 ¡ig
Cd/g) harvested after 5 weeks in solution containing
0.10 ¡ig Cd/ml.
TABLE 3.Cadmium contents of lettuce roots grown in ar
redondo FINE SAND.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
100
Avg
Zig/g
0
0
1.3
0.7
0.5
0.8
2.5
0
15.6
8.4
10.9
11.6
5.0
0
22.2
19.7
16.1
19.3
Avg
13.0
9.6
9.2
10.6
0
100
2.3
3.1
4.4
3.3
2.5
100
8.8
13.3
13.5
11.9
5.0
100
16.8
15.7
20.8
17.8
' Avg
9.3
10.7
12.9
11.0
Significant differences:
P < 0.001Cd, SS x Zn.
P < 0.05SS x Cd x Zn.
Cd added
kg/ha
SS added
tons/ha
0
Zn added, kg/ha
50 100
Avg
0
0
2.2
2.3
g/pot
2.2
2.2
2.5
0
2.2
2.3
2.2
2.2
5.0
0
2.0
2.5
2.2
2.2
Avg
2.1
2.4
2.2
2.2
0
100
1.7
1.8
1.5
1.7
2.5
100
1.8
1.6
1.4
1.6
5.0
100
1.7
1.8
1.5
1.7
Avg
1.7
1.7
1.5
1.6
Significant differences:
P < 0.001-SS.
P < 0.01SS x Zn.
P < 0.05Zn.
Radish root weights were decreased by SS and Zn
application at the highest rate (Table 6) and there was
a significant SS x Zn interaction. There was about 41 %
reduction in oven-dry weight of radish roots and a cor
responding 47% reduction in fresh weight (from 48
g/pot to 26 g/pot) from the addition of SS. However,
dry matter in the roots was increased from 6.6 to 7.8%
by the addition of SS. It is postulated that TSS in the
SS treated soil caused the reduction in radish top and
root yields (a further discussion of this follows in the
Soil section).
The radish roots (Table 7) contained about 20%
of the level of Cd contained in the lettuce roots (2.1
vs 10.8 ¡xg/g). It is highly unlikely that Cd toxicity
from radish with Cd levels would pose a problem in
the human diet.
Soil
The Arredondo fine sand used in this study had pH
5.9 in water and contained 5.9 ¡ig P/g, 24 ¡xg K/g, 24
fig Ca/g, and 92 fig Mg/g extracted in IN NH.jOAc
(pH 4.8). The SS was obtained from the Walt Disney
TABLE 5.Cadmium contents of radish tops grown in ar
redondo FINE SAND.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
100
Avg
ZZg/g
0
0
2.2
0.8
1.0
1.3
2.5
0
34.5
17.2
17.4
23.0
5.0
0
55.5
34.7
31.6
40.6
Avg
30.7
17.6
10.9
19.7
0
100
1.7
2.7
3.0
2.5
2.5
100
18.3
24.1
21.8
21.4
5.0
100
40.3
34.5
36.8
37.2
Avg
20.7
20.4
20.5
20.5
Significant differences:
P < 0.001Cd, Zn, SS x Zn, Cd x Zn, SS x Cd x Zn.


Proceedings, Volume 39, 1980
TABLE 6.Influence of Cd, SS, and Zn on dry matter yield of
RADISH ROOTS.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
100
Avg
0
0
3.2
3.2
2.9
3.1
2.5
0
3.5
3.1
3.3
3.3
5.0
0
2.9
3.4
3.1
3.1
Avg
3.2
3.2
3.1
3.2
0
100
2.1
2.2
1.7
2.0
2.5
100
2.3
1.8
1.3
1.8
5.0
100
2.0
2.3
1.8
2.0
Avg
2.1
2.1
1.6
1.9
Significant differences:
P < 0.001-SS.
P < 0.01Zn.
P < 0.05SS x Zn.
World sewage treatment plant and it measured pH
5.4 in water and contained total amounts of 60/Xg P/g,
500 /j.g K/g, 2,500 fig Ca/g, and 3,300 fig Mg/g. The
EC was 6.56 mmhos/cm which indicated a TSS content
that would restrict yields of most food crops (USDA
Handbook No. 60, 1954). The SS produced at Walt
Disney World is entirely from human activity and con
tains no industrial component. The DTPA-extractable
Cd in this SS was 2.7 jug/g and the Zn was 151 fig/g,
both of which are quite low values as compared to
other municipal SS (Chicago SS used in another of my
studies contained 25 fig Cd/g and 925 ¡xg Zn/g).
The Cd content of Arredondo fine sand at the end
of 16 weeks and after two harvests (Table 8) indicated
a large increase from Cd applications with no signif
icant effect from SS application. Evidently, the small
amount of Cd in the SS was not enough to effect a
change in soil Cda total of 270 g Ccl/ha was added by
the 100 tons/ha rate of SS. However, there was a sig
nificant SS x Cd interaction.
Total soluble salts were more than doubled by SS
TABLE 7.Cadmium contents of radish roots crown in ar
redondo FINE SAND.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
100
Avg
0
0
0.3
0.3
0.3
0.3
2.5
0
4.0
1.6
1.4
2.3
5.0
0
7.2
3.9
2.7
4.6
Avg
1
3.9
1.9
1.5
2.4
0
100
0.9
0.5
0.4
0.4
2.5
100
1.5
1.7
1.7
1.6
5.0
100
3.2
3.6
3.2
3.3
Avg
1.8
1.9
1.8
1.8
Significant differences:
P < 0.001Cd, SS, Zn, SS x Cd, SS x Zn, Cd x Zn, SS x Cd
x Zn.
61
TABLE 8.Cadmium contents of arredondo fine sand extracted
IN DTPA at the end of experimental period OF 16 WEEKS.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
100
Avg
0
0
0.06
0.09
0.06
0.07
2.5
0
1.17
1.56
1.26
1.26
5.0
0
2.54
2.68
2.68
2.63
Avg
1.26
1.38
1.33
1.32
0
100
0.24
0.29
0.24
0.26
2.5
100
1.20
1.22
1.24
1.22
5.0
100
2.26
2.43
2.36
.2.35
Avg
1.23
1.31
1.28
1.28
Significant differences:
" P< 0.001-Cd, SS x Cd.
P < 0.05Zn.
TABLE 9.Total soluble salts in arredondo fine sand at the
END OF THE EXPERIMENTAL PERIOD OF 16 WEEKS.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
100
Avg
hos/rm
0
0
1.45
1.21
1.58
1.41
2.5
0
1.21
1.50
1.11
1.27
5.0
0
1.50
1.07
1.16
1.24
Avg
1.39
1.26
1.28
1.31
0
100
2.95
2.66
3.29
2.97
2.5
100
2.17
3.00
3.24
2.80
5.0
100
2.83
2.59
2.87
2.76
Avg
2.65
2.75
3.13
2.85
Significant differences:
P < 0.001-SS, Cd x Zn.
P < 0.05SS x Zn.
application to Arredondo fine sand (Table 9). Accord
ing to the USDA Handbook No. 60, these levels of SS
could restrict germination and yield of salt sensitive
crops, i.e., soil with an EC > 2 and < 4 mmhos/cm.
Lettuce has moderate salt tolerance and radish sensi
tive salt tolerance (Lunin et al., 1960) and both species
should have displayed some effects of salt injury from
the SS. However, no symptoms of phytotoxicity in any
plant were attributable to TSS. As shown in Tables 4
and 6, soil containing SS produced yields of radish
tops and roots that were 25 and 41% lower than soil
with no SS. The sensitivity of radish to soluble salts
could have caused this reduction in yield.
LITERATURE CITED
1. Axelsson, B., and M. Piscator. 1966. Renal damage after pro
longed exposure to cadmium. Arch. Environ. Health 12:360-
373.
2. Carroll, J. M. 1965. The relationship of cadmium to cardio
vascular disease rates. J. Am. Med. Assoc. 198:177-179.
3. Haghiri, F. 1974. Plant uptake of cadmium as influenced by
cation exchange capacity, organic matter, zinc, and soil tem
perature. J. Environ. Qual. 3:180-183.


Soil and Crop Science Society of Florida
62
4. Lindsay, W. L. 1972. Zinc in soils and plant nutrition. Adv.
Agron. 24:147-186.
5. Lunin, Jesse, M. H. Gallatin, C. A. Bower, and L. V. Wilcox.
1960. Use of brackish water for irrigation in humid regions.
ARS, USDA Agrie. Inf. Bull. 213.
6. Maclean, A. J. 1976. Cadmium in different plant species and
its availability in soils as influenced by organic matter and
additions of lime, P, Cd, and Zn. Can. J. Soil Sci. 56:129-188.
7. Shroeder, H. A. 1965. Cadmium as a factor in hypertension.
J. Chronic Dis. 18:647-656.
8. Tauchiya, K. 1969. Causation of ouch-ouch (itai-itai byo)
Part 1, Keio, J. Med. 18:181-194.
9. Turner, M. A. 1973. Effect of cadmium treatment on
cadmium and zinc uptake by selected vegetable species. J.
Environ, Qual. 2:118-119.
10. U. S. Environmental Protection Agency, Solid Waste Disposal
Facilities. 1978. Proposed classification criteria. Fed. Regist.
43(25) :4942-4955.
11. U. S. Salinity Laboratory Staff. 1954. Determination of the
properties of saline and alkali soils, p. 7-16. In L. A. Richards
(ed.) Diagnosis and improvement of saline and alkali soils.
Agrie. Flandbook No. 60, USDA. U. S. Government Printing
Office, Washington, D. C.
12. Yamegata, N and I. Shigematsu. 1970. Cadmium pollution in
perspective. Inst. Public Flealth 19(1): 1 -27. Tokyo, Japan.
Genesis of Acid Sulfate Soils1
S. C. Hodges and V. W. Carlisle2
ABSTRACT
The objective of this paper was to bring together
pertinent views regarding the genesis of acid sulfate
soils. Acid sulfate phenomena commonly occur in soils
derived from recent marine sediments. Historical and
current concepts discussing genesis, chemistry, and en
vironment of iron sulfide formation are reviewed in
detail. Suggestions are made to refine the definition of
sulficlic materials, presently restricted to 0.75% or
more total S and less than three times as much car
bonate (CaC03 equivalent) as S, to the extent that the
extreme acidification of sandy soils similar to condi
tions occurring along Florida coastal areas could also
be recognized.
Additional Index Words: Sulfides, Pyrites, Sulficlic
materials, Sulficlic subgroups.
Acid sulfate soils were recently defined by Pons
(1972) to include all soil materials in which, during the
process of soil formation, H,S04 either was produced,
is being produced, or will be produced in amounts that
have lasting effect on the main soil characteristics. This
definition includes such soil materials as sulfidic and
sulfuric horizons and the traditional cat clays and cat
sands. Acid sulfate soils have a broad world-wide dis
tribution (Kawalec, 1972) but usually occur along
coastal areas of fairly recent marine sediments. Prior to
drainage, acid sulfate soil materials contain large
amounts of sulfide-S, primarily in the form of pyrite.
After drainage, the pyrite oxidizes, producing H2S04.
Pyrite oxidation often results in formation of jarosite
mottles and soil reaction of less than pH 4.0.
FORMATION OF IRON SULFIDES
In order for acid sulfate compounds to form, S and
Fe sources must exist together in a reducing environ
ment. Furthermore, a mechanism whereby alkaline
components are removed from the environment must
be' active. These conditions are usually present only
i Florida Agricultural Experiment Stations Journal Series No.
2335.
^Graduate Student and Professor of Soil Science, respectively,
Soil Science Department, University of Florida, Gainesville, FL
32611.
in marine sedimentary environments, although notable
exceptions have been reported (Chenery, 1954). Thus,
this paper emphasizes the marine environment in dis
cussing formation of sulfidic compounds.
Sulfur may originate from SO,2- in seawater, an
cient S-bearing formations, or biological materials. In
recent deltaic and coastal formations, areas which are
often agriculturally important, S042~ from seawater
was the primary source of S which formed sulfides
(Bloomfield and Coulter, 1975). Acid sulfate soils at
an elevation of 2000 m were reported by Chenery
(1954) where S-rich drainage waters from surrounding
schists and phyllites moved into inland swamps and
were reduced to sulfides. Extreme acidification resulted
when these soils were experimentally drained. Oxida
tion of sulfides in other ancient sediments may create
serious problems in coal, pyrite, copper, zinc, and lead
mines (Temple and Koehler, 1954). Sombatpanit3 de
scribed sulfidic soils in Sweden that contained S de
rived from biological materials that were simultane
ously deposited with finer mineral particles.
Of the more than 40 S compounds recognized by
Valenski (1950) to occur in the S-H,0 system, only
rhombic S, H2S, S042-, bisulfide, and bisulfate were
shown to occur in important quantities. Mohr et al.
(1972) used equilibrium pH-Eh diagrams to show the
dominance of S042- in aqueous solutions. Hydrogen
sulfide and HS~ are stable only under strongly reduced
conditions, whereas rhombic S is stable under very
specific conditions of Eh, pH, and total dissolved S
activity. Other investigators have extended this argu
ment to include natural environments such as seawater
(Berner, 1965; Garrels and Thompson, 1962; Rickard,
1971).
The compound H2S and HS anions react readily
with most Fe minerals to form Fe sulfides. Many Fe-
rich minerals have been reported in marine sedimen
tary environments. Equilibrium pH-Eh diagrams have
been used to show the stability of common dissolved
and solid Fe species in low temperature environments
(van Beers, 1962; Garrels and Christ, 1965; Mohr et ah,
1972; Rickard, 1971). These diagrams generally dem
onstrate that under the oxidized, neutral to alkaline
conditions of marine environments, hematite is the
3S. Sombatpanit, 1970. Acid sulfate soils, their nature and
properties. Unpubl. Thesis. Royal Agrie. Col., Uppsala.


63
Proceedings, Volume 39, 1980
stable Fe phase. Rickard (1971) noted, however, that
such diagrams usually do not consider goethite,
aqueous Fe(OH);i, and Fe silicates in the necessary cal
culations. James (1966) indicated that goethite is the
dominant Fe mineral formed under marine conditions.
Berner (1969) and Langmuir (1970) showed that
hematite is thermodynamically stable with respect to
goethite, but Berner (1969) concluded the conversion
rate was very slow and goethite may exist metastably at
lower temperatures. The relatively low solubility of Fe
oxides demonstrated by Garrels (1959) could be an
important factor in this slow conversion.
Stumm and Lee (1960) and Stumm and Morgan
(1970) discussed the polymerization of ferric Fe which
may subsequently lead to precipitation of insoluble
ferric hydrous oxides. They also noted that absorption
of poly-hydroxyl-metal complexes can occur against
electostatic repulsion forces. Thus, transportation of
Fe in natural waters has been reported as coatings on
clays (Carrol, 1958), coatings on sand grains (Berner,
1971), and living diatoms, plankton, and organic
debris (Harvey, 1936).
Thermodynamic data for Fe-silicate minerals such
as glauconite and chamosite are not available, but these
minerals may be important sources of Fe in the forma
tion of Fe sulfides (Berner, 1964; Mohr et al., 1972).
Other Fe minerals such as siderite (FeC03) and
vivianite [Fe3(PO4),-8H20] that are generally unstable
under conditions existing in marine environments
(Rosenquist, 1972; Berner, 1971), would be of im
portance only locally in the formation of sulfide min
erals. Many detrital Fe minerals under low tempera
ture and pressure will not react readily with sulfides.
Magnetite and ferro-magnesium silicates are par
ticularly resistant to sulfide attack (Rickard, 1971).
Some fine grained minerals may react and Menon
(1967) reported that diagenetic pyrite formed through
sulfidation of biotite Fe.
Sulfate Reduction
As noted above, S042~ is the principal form of S in
seawater. Since fixation occurs as sulfide, a reduction
process must take place. According to the calculations
of Stumm and Morgan (1970), it is thermodynam
ically possible for SO.,2 reduction to occur chemically
by an inorganic mechanism. Rickard (1971) pointed
out that this mechanism is very slow and probably in
significant. Sulfides may be released by decomposition
of naturally occurring organic S compounds, but
Berner (1970) noted that marine sediments often con
tain sulfides in excess of that amount which could be
theoretically calculated if the sediments were 100%
organic matter. A much more suitable explanation is
the presence of S042_-reducing bacteria, which are
capable of using S042-, S2032-, and S as electron ac
ceptors during oxidation of organic substances or H,
(Mohr et ah, 1972). Starkey (1966) postulated that
under natural circumstances SO.,2- reduction is entirely
a microbial process. Kimata et al. (1955) directly cor
related the percent sulfide by weight in a coastal mud
to the number of S042~-reducing bacteria present. The
reduction process may be represented by 2CH..0 +
SO,2- HCCV + HS- + C02 + HaO, where CH.O
represents a metabolizable organic substrate. It is im
portant to note that the reduction process increases pH
through the formation of bicarbonates.
Howarth (1979) recently demonstrated that, in the
surface peat of a Cape Cod salt marsh, S042- reduction
proceeds at very high rates. He concluded that S042-
reduction was the major form of respiration in salt
marsh ecosystems.
CHEMISTRY AND ENVIRONMENT OF
IRON SULFIDE FORMATION
Extremely limited amounts of authigenic, non-
ferrous sulficlic minerals have been observed in recent
sediments (Rickard, 1971). Thus, the primary method
of sulfide fixation is deposition as Fe sulfides. The
major Fe sulfide forms include pyrite (FeS2 cubic),
pyrrhotite (Fej_xS hexagonal), marcasite (FeS, ortho
rhombic), mackinawite (FeS tetragonal), griegite
(Fe3S4 cubic), and smythite (Fe3S4 rhombic). Of the
forms mentioned above, only pyrite and pyrrhotite are
thermodynamically stable in marine environments, al
though metastable forms of the other minerals may be
very persistent. Smythite may be stable at temperatures
below 75C (Rickard, 1971). Pyrrhotite forms at much
greater temperatures than pyrite, and thus is of little
importance in most recent sedimentary environments.
Rickard (1974) stated that the initial reaction in
sedimentary pyrite formation is between reactant Fe
(generally goethite) and dissolved sulfide. This results
in formation of a metastable ferrous or ferroso-ferric
sulfide. This material has been termed black FeS and
has been shown to contain both X-ray amorphous and
crystalline components. Mackinawite and griegite are
the only crystalline phases that have been identified at
the present time (Berner, 1964; Rickard, 1971; Rickard,
1975; Sweeney and Kaplan, 1973). Beyond this point,
more than one possible pathway exists. Sweeney and
Kaplan (1973) discussed the formation of pyrite result
ing from the reaction of mackinawite with elemental S
in the presence of 02. As a result of the reaction,
greigite is formed, which eventually yields framboidal
pyrite. Berner (1969) pointed out that natural pyrite-
forming systems are characterized by the presence of
dissolved sulfide as well as FeS and elemental S. Thus,
Rickard (1971; 1975) and Roberts et al. (1969) de
scribed a possible pathway for pyrite formation which
involved sulfidation of the FeS in the presence of dis
solved sulfides, considered to be in a polysulfide form.
Rickard (1971) further noted that the metastable FeS2
form, marcasite, could be formed in addition to pyrite
in acid environments while pyrite formation was fav
ored in the neutral to alkaline conditions found in
most sedimentary environments.
Howarth (1979) stated that formation of Fe mono
sulfides is kinetically favored over pyrite formation
and, once formed, these monosulfides are gradually
converted to pyrite. He reported a very rapid reduction
of radiolabeled S042- with pyrite as the major end
product. Based on solubility products of the monosul
fide mackinawite (Ksp = 2.75 x 10s) and pyrite (Ksp
= 2.4 x 1028), he argued that formation of either was
dependent upon the activity of dissolved sulfides. At
low values of dissolved sulfides, monosulfides are un
dersaturated and do not form while pyrite is super
saturated and precipitates rapidly and directly. He
suggested that pH dependence observed in pyrite
formation may be related to pH effects on dissolved
sulfide activity.
Dispersed grains of Fe sulfides may form in geolog-


64
Soil and Crop Science Society of Florida
ically small environments, even in sediments which are
not completely anoxic (Rickard, 1971). The primary,
metastable Fe sulfides are, however, quite sensitive to
oxidation and thus will form and be preserved only in
highly reduced, neutral to alkaline systems with mod
erate dissolved sulfide concentrations. More stable
forms, notably pyrite, may persist under somewhat
more variable conditions. In discussing the factors
which limit formation of sedimentary pyrite, Berner
(1964) included: (1) availability of organic matter
metabolizable by S042~-reducing bacteria, (2) diffusion
of S042- into sediments, (3) total concentration and
reactivity of Fe, and (4) production of elemental S.
He concluded on the basis of observations from several
locations that metabolizable organic matter is most
often the factor limiting the formation of sedimentary
pyrite. Thus, vegetative growth may drastically in
fluence the amounts of sulfides fixed in a sediment.
Bloomfield and Coulter (1973) reviewed physical-
environmental factors involved in sulfide formation
such as physiography, climate, and vegetation. They
concluded that sulfidic soils may form in coastal areas
with saline or brackish water influence and most often
on Pleistocene terraces. A notable exception is the area
of high altitude swamps with adjacent sources of S042-
described by Chenery (1954). Brinkman and Pons
(1973) discussed the relationship of microrelief in
broad, mostly flattened areas with sulfide formation.
Deposition of sulfides may occur under a wide variety
of climatic conditions, but the largest and most agri
culturally important areas are limited to humid or
monsoonal zones of the tropics and humid temperate
climates.
Pyrite aggregates are not homogeneously distrib
uted throughout pyritic soils. Pons (1972) noted that
pyrite may occur in primary or secondary forms. Pri
mary pyrite is formed during or after sedimentation
from organic matter deposited with the mineral frac
tion of the sediment. Secondary pyrite is formed as a
result of organic matter which is added after deposition
by plant growth. Primary pyrite is evenly and finely
dispersed throughout the reduced sediment while sec
ondary pyrite is concentrated in decayed remnants of
roots or other vegetative matter. Brinkman and Pons
(1973) stressed that in most warm temperate and trop
ical climates, only econdary pyrite occurs in propor
tions large enough to give rise to acidic conditions
characteristic of acid sulfate soils.
It should be noted that pyrite formed in sediments
commonly occurs as spherical aggregates of pyrite
microcrystallites, resulting in a striking surface known
as framboidal texture. The genesis of these framboids
was considered by several authors (Berner, 1962; Far-
rand, 1970; Love and Amstutz, 1966; Rickard, 1970;
Sweeney and Kaplan, 1973). Most recently, Sweeney
and Kaplan (1973) demonstrated that framboids form
when some 02 is presi nt during the sulfidation of FeS,
causing griegite to be formed as an intermediate com
pound prior to the subsequent formation of pyrite.
GENESIS
Sulfur Compounds in Undrained
Soils and Sediments
Organic S is generally the most abundant form of
S in nonsulfidic sediments, but it is quantitatively in
significant in pyrite sediments and acid sulfate soils
(Berner, 1963; Kaplan et al., 1963; van Breemen and
Harmsen, 1975). Elemental S may be produced in sig
nificant cpiantities under special conditions by chem
ical and microbial oxidation of H2S (Ljuggren, 1960;
Silverman and Ehrlich, 1964). It may frequently be
found in seabottom sediments, but is generally less
than 2% of the total S present (Berner, 1963; Kaplan
et al., 1963). Bloomfield (1972a) demonstrated that
oxidation of Fe sulfides may produce elemental S also,
but it is maintained at low concentration by microbial
and chemical activity. Of the forms of Fe sulfides
previously mentioned (see section on formation chem
istry), Mohr et al. (1972) concluded that the most im
portant Fe sulfides in marine environments, and thus
in undrained acid sulfate soils, are mackinawite,
griegite, and pyrite. Amorphous FeS may also be im
portant, but is rapidly transformed to one of these
more stable crystalline forms. In reduced acid sulfate
soils, hydrotroilite (FeS-nHzO) and melnikovite (FeS2
nH20) have been reported (van Beers, 1962). Un
drained sulfidic soils may contain as much as 5%
pyrite-S (van Breemen, 1973), but amounts between 1
and 4% are most common (Bloomfield, 1972b). Other
FeS compounds generally comprise less than 0.01%
and rarely exceed 0.6% of the soil. Wilklander et al.
(1950) demonstrated that FeS compounds may cause
acidification in some gytta soils in Sweden and Finland.
This was attributed to a low total S content which in
hibited pyrite formation.
Oxidation of Sulfides
Oxidation of FeS proceeds rapidly in the presence
of O,, yielding elemental S and ferric oxide. Bloomfield
(1972b) noted that if microbial conditions were favora
ble, elemental S was rapidly oxidized to S042-. Many
sulfate minerals are associated with oxidizing sulfidic
materials, but most are very soluble and form only in
absence of leaching (Palache et al., 1951). The oxida
tion of pyrite is purely chemical. Using pyrite stability
diagrams, van Breemen (1973) concluded that O, and
Fe3+ are the only two oxidants active in pyrite oxida
tion under natural conditions. Some investigators
(Hart, 1962; van Breemen, 1973) indicated the initial
products of pyrite oxidation are elemental S and Fe2+
while others (Bloomfield, 1972b; Garrels and Thomp
son, 1960; Silverman, 1967) reported that S042~ is re
leased essentially instantaneously during pyrite oxida
tion by Fe3+. Elemental S is released at higher pH
values for this oxidation pathway.
Van Breemen (1973) maintained that chemical
oxidation of pyrite proceeds in the following sequence:
FeS2 + 1/2 O., + 2H+-* Fe2+ + 2S + H,0 (a)
Fe2+ + 1/4 0, 4- H+ -> Fe3+ + 1/2 HaO (b)
FeS, + 2Fe3+ -> 3Fe2+ + 2S (c)
2S + 12Fe3+ + 8H,0 -> 12Fe2+ + 2S042- + 16H+ (d)
Reaction (a) describes the purely chemical oxidation of
pyrite by O,. Although this is a relatively rapid reac
tion, Singer and Stumm (1970) and Temple and Del-
champs (1953) demonstrated that it is a slow process
due to the sluggishness of pyrite oxidation in a sterile,
moist, aerated medium where Fe3+ was absent. At low
pH, when conditions are favorable for Fe3+ to remain
in solution, reaction (b) takes place very slowly. Above
pH 3.0 to 3.5, Fe3+ is precipitated as Fe(OH)3 leaving
insignificant amounts of Fe3+ in solution to react with


65
Proceedings, Volume 39, 1980
pyrites. Therefore, very little of the Fe released by
pyrite oxidation would occur as free Fe3+. Singer and
Stumm (1970) observed that only 5% of the ferrous
Fe content of an acidic solution originally containing
9 x 10-4 M Fe2+ was oxidized in 150 days. Thus, some
means of oxidation of Fe2+ at low pH is required for
rapid oxidation of pyrite. This is achieved by micro
bial activity. Many investigators (Lorentz, 1962) re
ported enhancement of pyrite oxidation by the pres
ence of certain microorganisms. Thiobacillus ferro-
oxidans was identified in acid mine waters (Leathen
and Madison, 1949) and later found to be capable of
oxidizing Fe2+ under very acid conditions. Silverman
and Ehrlich (1964) reviewed the interactions of micro
organisms and minerals, indicating that Thiobacillus
species were responsible for most large-scale biological
oxidation of elemental S to form SO,2-. Van Breemen
(1973) noted that, although generally obligate aerobic
autotrophs, Triobacillus species were surprisingly wide
spread and concluded that under favorable conditions
in natural environments, microbial activity is generally
not a limiting factor in pyrite oxidation. Bloomfield
(1972b) pointed out that optimum pyrite oxidation re
quired moist soils and that microbial activity slowed
drastically in air dry soils. In addition, Silverman (1967)
observed that Cl- also had an inhibitory effect on bac
terial oxidation of pyrite. In the presence of Fe3+, both
pyrite and elemental S are rapidly oxidized according
to reactions (c) and (d). The combined process of these
reactions
FeS2 + 14Fe3+ + 8H20 15Fe24 + 2S042- + 16H4,
takes place rapidly at room temperature (Garrels and
Thompson, 1960; Singer and Stumm, 1970).
Physical Factors Affecting Pyrite Oxidation
Several investigators have recognized a positive
effect of decreased particle size on pyrite oxidation rate
(Hart, 1962; Quispel et al., 1952; Temple and Del-
champs, 1953). This was attributed to lattice defects
(van Breemen and Harmsen, 1975) and to increased
surface area which increased reactivity (Stumm and
Morgan, 1970). Harmsen et al. (1954) described soils
containing significant amounts of pyrite that had not
acidified after drainage. They postulated that several
different polysulficle fractions contributed to the stabil
ity of the pyrite, but gave no chemical or mineralogical
evidence as support. Van Breemen (1973) suggested
that preservation was due to the large particle size
(between 10 and 100 /m in diameter), combined with
relatively high pH. At higher pH, a protective coating
of Fe.X), may form, thus slowing the oxidation rate.
Hodges4 observed such coatings on pyrite framboids
taken from a Florida soil. Harmsen et al. (1954) and
Quispel et al. (1952) reported that high levels of dis
solved P strongly depressed the decomposition of
pyrite at pH values above 4 due to precipitation of
Fe3+ as FeP04. An additional factor influencing pyrite
oxidation is the O, diffusion rate. Van Breemen (1973)
calculated that only 10% of the O, required for op
timum pyrite oxidation is capable of diffusing into a
reduced soil from the atmosphere.
4S. C. Hodges, 1977. Acid sulfate phenomena in a selected
Florida Alfisol. M. S. Thesis. University of Florida, Gainesville.
Acidification, Buffering, and Formation
of Solid Sulfate Minerals
Oxidation of S compounds and especially pyrite
has been studied extensively in relation to acid sulfate
soil formation (Bloomfield, 1972a; Bloomfield, 1972b;
Harmsen et al., 1954; Hart, 1962; Quispal et al., 1952;
van Breemen, 1973). Samples oxidized under moist
laboratory conditions usually resulted in lower pH
values than soils oxidized in the field. Chenery (1954)
and van Breemen (1973) reported reaction values as
low as pH 1.2 and 1.8 to 2.5 for laboratory dried
samples. Typical field values for oxidized horizons
range between pH 3.0 and 4.0 (Calvert and Ford, 1973;
Chenery, 1954; Clark et al., 1961; Coultas and Calhoun,
1976; Fleming and Alexander, 1961; van Breemen,
1973; van Breemen and Harmsen, 1975), although
James (1966) observed a low reaction of pH 1.5 in
poorly buffered sands of mining spoils. According to
van Breemen (1973), this typical range indicated that
the pH was buffered and the pH of an oxidized acid
sulfate soil was dependent upon the buffering charac
teristics of the soil. Buffering may result from inter
action of acid with alkalinity in soil solutions, ex
changeable bases, and soil minerals, including clay
minerals.
In non-alkaline soils, interstitial waters would be
capable of neutralizing acidity produced by pyrite
oxidation only over very long periods and under in
tense leaching conditions. This was attributed to the
low levels of alkalinity dissolved in such soils (van
Breemen, 1973). Exchangeable bases may be replaced
by H+ as the pH decreases, resulting in the formation
of non-exchangeable acidity. Sombapatnit3 compared
the CEC at pH 7.0 with CEC at pH 3.5 to 4.0 of sev
eral acid sulfate soils and concluded that 10 to 30 meq
of acidity were adsorbed by the exchange complex. At
low pH, H+ may react with lattice OH groups releasing
Al3+; thus, there is not a definite boundary between
exchange reactions and mineral transformations.
Silica minerals provide no buffering and kaolinite
provides buffering only at very low pH (van Breemen,
1973). Micas and feldspars may remove acidity from
the soil by reaction of lattice OH groups. The most
important minerals in buffering acidity are carbonates
such as calcite and aragonite. These minerals are dis
solved by strong acids to produce divalent metal
cations, C02 and H20. As long as carbonate materials
remain in the immediate environment, the reaction of
the soil remains close to pH 7.0. As more acid is pro
duced, Ca2+ and S042- may either remain in solution or
precipitate as gypsum [CaS0,-2H20], depending on the
moisture content of the soil.
As carbonates or other bases are removed from the
system, minerals containing basic metal hydroxides or
sulfates may form. The most common minerals of the
latter group are members of the jarosite group. Accord
ing to Palache et al. (1951) this group is composed of
three end members, jarosite [KFe3(S04)2(0H)6], natro-
jarosite [NaFe3(S04)2(0H)6], and the rare hydronium
jarosite [(H30)Fe3(S4)2(0H)6]. Brophy and Sheridan
(1965) and van Breemen (1973) demonstrated a strong
preference for K+ over Na+ and H.O4 in the jarosite
group. Natrojarosite was formed only after near com
plete depletion of available K in laboratory experi
ments (van Breemen, 1973). Hydronium jarosite is rare
and should theoretically occur only at very low K con-


66
Soil and Crop Science Society of Florida
centrations and reaction values less than pH 2.0, al
though Brophy and Sheridan (1965) presented evi
dence that it may form as a metastable product upon
rapid oxidation. Jarosite is pale yellow, insoluble in
water and commonly found along old root channels,
on ped faces, and on drainage spoils (Bloomfield and
Coulter, 1973). It is stable only under strong oxidizing
and acid conditions. Under reducing conditions,
jarosite dissolves, yielding K+, Fe2+, and SO,-'. Bloom
field and Coulter (1973) stated that above pH 3.0,
jarosite hydrolyzed to give Fe.,03, SO.,2-, and K+. In
soils jarosite may occur above pH 4.0, perhaps as a
result of very acid microenvironments in the immedi
ate vicinity.
Warshaw (1956) suggested that jarosite is directly
precipitated as oxidation and leaching take place in
sulfidic sediments. Furbish (1963) has reported direct
psuedomorphic alterations from pyrite to jarosite. Van
Breemen and Harmsen (1975) however, observed that
oxidizing pyritic soils often develop a reddish-brown
surface coating prior to formation of the typical yellow
efflorescences of jarosite. They suggested that ferric
hydroxide may form as an intermediate step in jarosite
formation. In addition to jarosite, van Breemen (1973)
postulated that a basic, perhaps amorphous, aluminum
sulfate with the formula Al(OH)SO., was present in
acid sulfate soils of Sarawak. Ivarson et al. (1978) re
ported that amorphous basic sulfates formed under
laboratory conditions in the absence of K+, NH.,+, or
Na+. Bloomfield and Coulter (1973) reviewed occur
rences of other Al sulfate minerals in soils and con
cluded that definitions of these compounds are at
present only speculative.
After all carbonates have been removed from the
system and formation of reaction products proceeds,
metal-aluminum-silicate clays begin to react with the
acid produced by pyrite oxidation and cause further
buffering of the soil pH. These clays react with the
acid, releasing metal ions, monomeric silica, and often
an aluminosilicate residue such as kaolinite. Van
Breemen (1973) discussed the equilibrium system
montmorillonite-amorphous silica-H30 using a thermo
dynamic approach. This system resulted in a very
strong buffering capacity between pH 3.0 and 4.0. If
amorphous silica did not precipitate, buffering capacity
was drastically reduced. Using similar data for other
systems, it was concluded that buffering intensity was
very high for calcite; moderately high for Mg-
chlorite, montmorillonite-amorphous silica, kaolinite-
amorphous silica; and very low for Mg-montmoril-
lonite and kaolinite in the absence of amorphous silica.
Calcite and Mg-chlorite buffer the soil at high pH,
whereas the remaining systems result in buffering only
at low pH. These buffering reactions may cause
changes in the clay mineral fraction of acid sulfate
soils. Lynn and Whittig (1966) stated that chlorite was
transformed to montmorillonite in an acid sulfate soil
drained 60 years ago. Allbrook (1972) described a
change from montmorillonite to interstratified mont-
morillonite-vermiculite and quartz mineralogy for acid
sulfate soils in Sarawak. Kaolinite has often been re
ported as the dominant clay mineral in oxidized trop
ical acid sulfate soils (Allbrook, 1972; Anclriesse et al.,
1972; van Beers, 1962; van Breemen, 1973). Buurman
et al. (1973) noted formation of kaolinite at the ex
pense of 2:1 clay minerals in a fossil acid sulfate soil of
Germany. Ivarson et al. (1978) showed stoichiometric
removal of K+ or N H4+ from glauconite, illite, or
mi crocline upon formation of basic Fe,(SO,)3 in labora
tory experiments. They concluded that the cation re
quired for jarosite formation could be furnished by
alteration of these minerals.
Profile Development
If soils containing pyrite remain reduced, little
change takes place other than transformation of other
sulfides to pyrite, recrystallization of pyrite, and some
loss of water (Brinkman and Pons, 1973). In unclrained
sediments, pyrite content has been observed to increase
with depth in the upper 100 to 150 cm (Allbrook,
1972; Andriesse et al., 1972; van Breemen et al., 1972).
Upon drainage, these soils enter into a geologically
transient state with acid production, neutralization or
leaching, and profile development occurs within a
period of a few years to a hundred or so years. Vlek
(1971) and van Breemen and Harmsen (1975) dis
cussed profile development in soils of varying age and
parent material in Thailand. In the youngest soils,
shallow drainage resulted in acidification of the sur
face, but formation of jarosite had not begun. In young
soils (prior to intense acidification) amorphous Fe
(OH)3 occurred. Ponnamperuma et al. (1967) found
this to be the dominant Fe form in hydromorphic soils.
As oxidation increased, a jarositic horizon formed
above the reduced pyritic horizon. The horizons were
observed to move progressively downward with time.
Vlek (1971) noted an abrupt boundary between the
jarosite horizon and the pyritic horizon and concluded
that oxidation was confined to a narrow layer. Where
jarosite and pyrite occurred together, jarosite appeared
in pyrite-free vertical zones along root channels and
cracks which penetrated into the reduced soil. The
author further postulated that the amount of jarosite
present depended in part upon the number of such
sites available for precipitation. Hydrolysis of jarosite
in the upper horizons resulted in accumulations of
Fe203. Van der Kevie (1972) recognized acid sulfate
soils in Sarawak, which did not contain jarosite, al
though they were very acid and high in S. Some
gypsum may occur in lower horizons, but most of the
S042- produced by pyrite oxidation is removed by
leaching or diffusion (Mohr et al., 1972; van Breemen,
1973, van Breemen and Harmsen, 1975). In addition,
poorly crystalline goethite, lepidocrocite, or hematite
may be present (van der Kevie, 1972).
Relatively high pFI values have been observed in
surfaces of older acid sulfate soils (Mohr et al., 1972;
van Breemen, 1973; Vlek, 1971). Van Breemen (1973)
suggested that these resulted from (1) disappearance
of jarosite, (2) slow back titration of acidity by
weathering of soil minerals still present, and (3) effects
of fresh sediment and/or dissolved alkalinity in the
ground water.
CLASSIFICATION OF ACID SULFATE SOILS
Soil Taxonomy (Soil Survey Staff, 1975) distin
guishes between acid sulfate soils that have been oxi
dized and acidified and those that remain in a reduced
state. The first must contain a sulfuric horizon (pH
<3.5 and jarosite mottles) while the latter is made up
of soils containing sulfidic materials (0.75% or more


67
Proceedings, Volume 39, 1980
total S in sulfidic form and less than three times as
much carbonate as S). Mineral soils with a sulfuric
horizon within 50 cm of the surface would be classified
as Sulfaquepts. Those soils with a sulfuric horizon
between 50 cm and 150 cm are recognized as sulfic sub
groups of Haplaquepts or Tropaquepts. Organic soils
containing sulfidic materials within 1 m of the surface
are classified as Sulfihemists. Organic soils with sulfuric
horizons within 50 cm of the surface are classified as
Sulfohemists.
Presently, reduced acid sulfate mineral soils are
designated as Sulfaquents if they have sulfidic materials
within a depth of 50 cm below the mineral soil surface.
Sulfic subgroups have been recognized and defined for
Fluvaquents and Haplaquents.
Problems with the current classification scheme
have been noted by several authors. Van der Kevie
(1972) suggested that the definition of a sulfuric
horizon be changed so that those soils with extreme
acidity and no jarosite mottles could be recognized.
Such soils have been observed by van der Kevie (1972)
in Sarawak and by Hodges4 in Florida. Coultas and
Calhoun (1976) found high levels of soluble salts in
marsh soils of Florida and concluded that a refinement
of taxonomy is needed to emphasize this property.
Coover et al. (1975) as well as van der Kevie (1972)
also indicated a need for such a refinement and sug
gested the inclusion of Halic subgroups in the current
taxonomy. Coover et al. (1975) regarded the current
definition of sulfidic materials, especially for organic
soils, as inadequate due to the failure of these soils to
acidify upon drainage in some coastal marshes of the
southeastern United States. Hodges4 noted that levels
of total S much lower than the defined level of 0.75%
may result in extreme acidification of sandy soils.
LITERATURE CITED
1. Allbrook, R. F. 1972. The identification of acid sulphate soils
in Northwest Malaysia, p. 131-140. In H. Dost (ed.) Acid
sulphate soils, ILRI Publ. 18, Vol. II. Int. Inst, for Land
Reclamation and Improvement, Wageningen, The Nether
lands.
2. Andriesse, J. P., N. van Breemen.and W. A. Blokhuis. 1972.
The influence of mudlobsters (Thalassina anomale) on the
development of acid sulfate soils in mangrove swamps in
Sarawak (East Malaysia), p. 11-39. In H. Dost (ed.) Acid
sulphate soils, ILRI Publ. 18. Vol. II. Int. Inst, for Land
Reclamation and Improvement, Wageningen, The Nether
lands.
3. Berner, R. A. 1962. Experimental studies of the formation of
sedimentary iron sulfides, p. 107-120. In M. L. Jensen (ed.)
Biogeochemistry of sulfur isotopes. National Sci. Found.
Symp. Yale Univ. Press, New Haven, Conn.
4. Berner, R. A. 1963. Electrode studies of hydrogen sulfide in
marine sediments. Geochim. Cosmochim. Acta 27:563-575.
5. Berner, R. A. 1964. Iron sulfides formed from aqueous solu
tions at low temperatures and atmospheric pressure. J. Geol.
72:826-834.
6. Berner, R. A. 1965. Activity coefficients of bicarbonate, car
bonate and calcium ions in seawater. Geochim. Cosmochim.
Acta 29:947-968.
7. Berner, R. A. 1969. Goethite stability and the origin of red
beds. Geochim. Cosmochim. Acta 33:267-273.
8. Berner, R. A. 1970. Sedimentary iron formation. Am. J. Sci.
268:1-23.
9. Berner, R. A. 1971. Principles of chemical sedimentology.
McGraw Hill, Inc., New York.
10. Bloomfield, C. 1972a. Acidification and ochre formation in
pyrite soils, p. 41-51. In H. Dost (ed.) Acid sulphate soils.
ILRI Publ. 18, Vol. II. Int. Inst, for Land Reclamation and
Improvement, Wageningen, The Netherlands.
11. Bloomfield, C. 1972b. The oxidation of iron sulfides in soils
in relation to the formation of acid sulfate soils and ochre
deposits in field drains. J. Soil Sci. 23:1-16.
12. Bloomfield, C., and J. K. Coulter. 1973. Genesis and manage
ment of acid sulphate soils. Adv. Agron. 25:265-326.
13. Brinkman, R., and L. J. Pons. 1973. Recognition and pre
diction of acid sulfate soil conditions, p. 169-203. In H. Dost
(ed.) Acid sulphate soils. ILRI Publ. 18, Vol. I. Int. Inst. Land
Reclamation and Improvement, Wageningen, The Nether
lands.
14. Brophy, G. D., and M. F. Sheridan. 1965. Sulfate studies, IV.
The jarosite-natrojarosite-hydronium jarosite solid solution
series. Am. Min. 50:159501607.
15. Buurman, P N. van Breemen, and A. G. Jongmans. 1973. A
fossil acid sulphate soil in ice-pushed tertiary deposits near
Uelsen, Germany, p. 52-75. In H. Dost (ed.) Acid sulphate
soils. ILRI Publ. 18, Vol. II. Int. Inst, for Land Reclamation
and Improvement, Wageningen, The Netherlands.
16. Calvert, D. V., and H. W. Ford. 1973. Chemical properties of
acid-sulfate soils recently reclaimed from Florida marshland.
Soil Sci. Soc. Am. Proc. 37:367-371.
17. Carrol, D. 1958. Role of clay minerals in the transportation
of iron. Geochim. Cosmochim. Acta 14:1-28.
18. Chenery, E. M. 1954. Acid sulfate soils in central Africa.
Trans. 5th Int. Cong. Soil Sci. 4:195-198.
19. Clark, J. S., C. A. Gobin, and P. N. Sprout. 1961. Yellow
mottles in some poorly drained soils of the lower Frase Valley,
British Columbia. Can. J. Soil Sci. 41:218-227.
20. Coover, J. R., L. J. Bartelli, and W. C. Lynn. 1975. Applica
tion of soil taxonomy on the tidal areas of the southeastern
United States. Soil Sci. Soc. Am. Proc. 39:703-706.
21. Coultas, C. L., and F. G. Calhoun. 1976. Properties of some
tidal marsh soils of Florida. Soil Sci. Soc. Am. J. 40:72-76.
22. Farrand, M. 1970. Framboidal sulphides precipitated syn
thetically. Min. Dep. 5:237-247.
23. Fleming, J. F., and L. T. Alexander. 1961. Sulfur acidity in
South Carolina tidal marsh soils. Soil Sci. Soc. Am. Proc. 25:
94-95.
24. Furbish, W. J. 1963. Geological implications of jarosite
psuedomorphic after pyrite. Am. Min. 48:703-706.
25. Garrels, R. M. 1959. Rates of geochemical reactions at low
temperatures and pressures, p. 25-37. In P. H. Abelson (ed.)
Researches in geochemistry. Wiley, New York.
26. Garrels, R. M., and C. L. Christ. 1965. Solutions, minerals,
and equilibria. Harper & Row, New York.
27. Garrels, R. M., and M. E. Thompson. 1960. Oxidation of
pyrite by iron sulfate solutions. Am. J. Sci. 258:56-67.
28. Garrels, R. M., and M. E. Thompson. 1962. A chemical model
for seawater at 25 C and one atmosphere total pressure. Am.
J. Sci. 260:57-66.
29. Harmsen, G. W., A. Quispel, and D. Otzen. 1954. Observa
tions on the formation and oxidation of pyrite in the soil.
Plant and Soil 5:324-347.
30. Hart, M. G. R. 1962. Observations on the source of acid in
empouldered mangrove soils. I. Formation of elemental sul
phur. Plant and Soil 17:87-98.
31. Harvey, H. W. 1936. The supply of iron to diatoms. J. Mar.
Biol. Assoc. 23:423.
32. Howarth, R. W. 1979. Pyrite: Its rapid formation in a salt
marsh and its importance in ecosystem metabolism. Science
203:49-51.
33. Ivarson, K. C., G. J. Ross, and N. M. Miles. 1978. Alteration
of micas and feldspars during microbial formation of basic
ferric sulfates in the laboratory. Soil Sci. Soc. Am. J. 42:518-
524.
34. James, A. L. 1966. Stabilizing mine dumps with vegetation.
Endeavor 25:154-157.
35. Kaplan, I. R., K. O. Emery, and S. C. Rittenberg. 1963. The
distribution and isotope abundance of sulfur in recent marine
sediments of Southern California. Geochim. Cosmochim. Acta
37:297-331.
36. Kawalec, A. 1972. World distribution of acid sulphate soils.
References and map. p. 293-295. In H. Dost (ed.) Acid sul
phate soils. ILRI Publ. 18, Vol. I. Int. Inst. Land Reclamation
and Improvement, Wageningen, The Netherlands.
37. Kimata, M., H. Kadota, Y. Hata, and T. Tajuma. 1955. Studies
of marine sulfate-reducing bacteria: I. Distribution of marine
sulfate reducing bacteria in coastal waters receiving a con
siderable amount of pulpmill drainage. Bull. Jap. Soc. Sci.
Fish. 21:104-108.
38. Langmuir, D. 1970. The effect of particle size on the re
action: hematite + water = goethite. Geol. Soc. Am. Abstr.
of Am. Meetings, 601-602.
39. Leathen, W. W., and K. M. Madison. 1949. The oxidation of
ferrous iron by bacteria found in acid mine waters. Soc. Am.


68
Soil and Crop Science Society of Florida
Bact., Abstracts of Papers, 64.
40. Ljuggren, P. 1960. A sulfur mud deposit formed through
bacterial transformation of flumarolic hydrogen sulfide. Econ.
Geol. 55:531-538.
41. Lorenz, W. C. 1962. Progress in controlling acid mine water:
A literature review. U. S. Ber. Mines Int. Cir. 8080.
42. Love, L. G., and G. C. Amstutz. 1966. Review of microscopic
pyrite from the Devonian Chattanooga Shale and Remmels-
berg Banderz. Fortschr. Miner. 43:273-309.
43. Lynn, W. C., and L. D. Whittig. 1966. Alteration and trans
formation of clay minerals during cat clay development. Clays
and Clay Min. 14:241-248.
44. Menon, K. K. 1967. Origin of diagenetic pyrite in the Quilon
Limestone, Kerala, India. Nature 213:1219-1220.
45. Mohr, E. C. J., F. A. van Baren, and J. van Schuylenborgh.
1972. Tropical soils. Mouton-Ichtiar Baru van Hoeve. The
Hague, The Netherlands.
46. Palache, C. H., H. Berman, and C. Frondell. 1951. The system
of mineralogy of J. D. and E. S. Dana. 7th ed., Vol. II. Wiley,
Chapman & Hall.
47. Ponnamperuma, F. N., E. M. Tianco, and T. Loy. 1967. Redox
equilibria in flooded soils: I. The iron hydroxide system. Soil
Sci. 103:374-382.
48. Pons, L. J. 1972. Outline of the genesis, characteristics, classi
fication and improvement of acid sulfate soils, p. 3-27. In
H. Dost (ed.) Acid sulphate soils. ILRI Publ. 18, Vol. I. Int.
Inst. Land Reclamation and Improvement, Wageningen, The
Netherlands.
49. Quispel, A., G. W. Harmsen, and D. Otzen. 1952. Contribu
tion to the chemical and bacteriological oxidation of pyrite
in soil. Plant and Soil 4:43-55.
50. Rickard, D. T. 1970. The origin of framboids. Lithos. 3:269-
293.
51. Rickard, D. T. 1971. Sedimentary iron sulfide formation, p.
28-65. In H. Dost (ed.) Acid sulphate soils. ILRI Publ. 18,
Vol. I. Int. Inst. Land Reclamation and Improvement,
Wageningen, The Netherlands.
52. Rickard, D. T. 1974. Sulfidation of geothite. Am. J. Sci. 274:
941-952.
53. Rickard, D. T. 1975. Kinetics and mechanisms of pyrite
formation at low temperature. Am. J. Sci. 275:636-652.
54. Roberts, W. M. B., A. L. Walker, and A. S. Buchanan. 1969.
The chemistry of pyrite formation in aqueous solution and
its relation to the depositional environment. Min. Dep. 4:
18-29.
55. Rosenquist, I. T. 1972. Formation of vivianite in holocene
clay sediments. Lithos. 3:327-334.
56. Silverman, M. P. 1967. Mechanism of bacterial pyrite oxida
tion. J. Bact. 94:1046-1051.
57. Silverman, M. P., and H. L. Ehrlich. 1964. Microbial forma
tion and degradation of minerals. Adv. Appl. Microbiol. 6:
153-206.
58. Singer, R. C and W. Stumm. 1970. Acidic mine drainage:
The rate-determining step. Science 167:1121-1123.
59. Soil Survey Staff. 1975. Soil Taxonomy: A basic system of soil
classification for making and interpreting soil surveys. Agri
cultural Handbook No. 436. U. S. Govt. Printing Office,
Washington, D. C.
60. Starkey, R. L. 1966. Oxidation and reduction of sulfur com
pounds in soils. Soil Sci. 101:297-307.
61. Stumm, W., and G. F. Lee. 1960. The chemistry of aqueous
iron. Schweiz. S. Hydrol. 22:295-319.
62. Stumm, W., and J. J. Morgan. 1970. Aquatic chemistry.
Wiley-Interscience, New York. 583 pp.
63. Sweeney, R. E., and I. R. Kaplan. 1973. Pyrite formboid
formation. Econ. Geol. 68:618-634.
64. Temple, K. L., and F. W. Delchamps. 1953. Autotrophic
bacteria and the formation of acid in butuminous coal mines.
Appl. Microbiol. 1:255-258.
65. Temple, K. L., and W. A. Koehler. 1954. Drainage from
butuminous coal mines. W. Va. Eng. Exp. Sta. Res. Bull. 25.
66. Valenski, G. 1950. Contribution an diagramme potentiel -pH
du soufre. C. R. Zieme Reunion Comm. Int. Therm. Kinetics
Electrochim. (Milan) :51-68 (Cited in Mohr et al., 1972).
67. van Beers, W. F. J. 1962. Acid sulphate soils. Int. Inst. Land
Reclaim. Impr. Bull. 3:1-31.
68. van Breemen, N. 1973. Soil forming processes in acid sulfate
soils, p. 66-130. In H. Dost (ed.) Acid sulfate soils. ILRI
Publ. 18, Vol. I. Int. Inst. Land Reclamation and Improve
ment, Wageningen, The Netherlands.
69. van Breemen, N., and K. Harmsen. 1975. Translocation of
iron in acid sulfate soils: I. Soil morphology and the chem
istry and mineralogy of iron in a chronosequence of acid
sulfate soils. Soil Sci. Soc. Am. Proc. 39:1140-1148.
70. van Breemen, N., M. Tandatemiya, and S. Chanchareonsook.
1972. A detailed survey on the actual and potential soil
acidity at the Bang Pakang Land Development Centre, Thai
land. p. 159-168. In H. Dost (ed.) Acid sulfate soils. ILRI
Publ. 18, Vol. II. Int. Inst. Land Reclamation and Improve
ment, Wageningen, The Netherlands.
71. van der Kevie, W. 1972. Physiography, classification, and
mapping of acid sulfate soils, p. 204-222. In H. Dost (ed.)
Acid sulfate soils. ILRI Publ. 18, Vol. I. Int. Inst. Land
Reclamation and Improvement, Wageningen, The Nether
lands.
72. Vlek, P. 1971. Some morphological, physical and chemical
aspects of acid sulfate soils in Thailand. Soil Surv. Rept. 84.
Land Dev. Dept., Thailand.
73. Warshaw, C. M. 1956. The occurrence of jarosite in under
clays. Am. Min. 41:288-296.
74. Wiklander, L G. Hallgren, N. Brink, and E. Jonsson. 1950.
Studies on gytta soils. II. Some characteristics of two profiles
from northern Sweden. Ann. Roy. Agrie. Coll. Sweden 17:
24-36.
Application of Ground Penetrating Radar to Soil Survey1
R. W. Johnson, R. Glaccum, and R. Wojtasinski2
ABSTRACT
Soil surveys are made by soil scientists walking over
the land and examining the soil with various kinds of
manual and mechanical probes and augers. The num
ber of observations made with these tools to classify
the soil and to determine soil boundaries is limited by
available time and money. Quality and quantity of
soil surveys could be improved if faster and less lab
orious methods were used.
The main purpose of this study was to demonstrate
iFlorida Agricultural Experiment Station Journal Series No.
.2392.
2State Soil Scientist, USDA, SCS, Gainesville, FL, 32602; Geo
chemist, Technos, Inc., Miami, FL, 33133; Electrical Engineer,
NASA, Kennedy Space Center, FL, 32899.
the feasibility of using ground penetrating radar (GPR)
in making soil surveys. Other objectives were to de
termine if improvements in the GPR system were
needed for this purpose, and to determine the best pro
cedures for using GPR in soil survey.
The GPR was tested at two locations in central
Florida. Both had order 2 soil surveys and had several
contrasting soils. Approximately 8 km of transects
were run with the GPR. Ground truth was made by
borings at intervals of 30 m along the lines of transect.
Data from both sources were compared with the soil
maps. The GPR data were generally of excellent
quality, accurately measuring the depth to and thick
ness of several kinds of soil horizons. We conclude that
GPR is an effective supplemental tool for surveying
certain kinds of soil.


69
Proceedings, Volume 39, 1980
Additional Index Words: Geophysical methods,
Ground proving radar, Soil remote sensing, Soil tax
onomy.
A variety of manual and mechanical augers and
probes are usually the basic tools used in examining
soils for making soil surveys and investigating hydro-
logic and geotechnical characteristics close to the
ground surface. The number of observations is limited
by time and money, but they are spaced to best define
the area being surveyed and are based on the soil sci
entists understanding of soil formation, vegetation,
natural drainage, topography, and other features in
the landscape. This work is highly labor-intensive and
relatively slow; additionally, the quality of the results
is a function of the variability of the area being map
ped. To improve the definition of a complex area, a
greater number of observations is required per unit
area. In these circumstances time limitations and costs
may become unreasonable or prohibitive. Remote
sensing techniques, primarily various types of airborne
imagery, have proved to be a valuable tool for deter
mining soil boundaries. However, imagery detects
properties of the soil surface and various kinds of
vegetation. While these are helpful, most properties
beneath the surface are of primary significance to the
classification, mapping, and interpretation of soils.
To circumvent the limitations of tools and imagery
presently used in soil survey, other options such as the
various geophysical (surface remote sensing) methods
were investigated as part of a cooperative project be
tween the Soil Conservation Service (SCS) and the
National Aeronautics and Space Administration
(NASA) at the Kennedy Space Center. Mechanical
systems investigated included sonar, geophysical sound
ing devices, and gravity techniques (Dobrin, 1960).
Some of the new methods allow subsurface information
to be gathered very rapidly and economically as well as
providing continuous line coverage of an area. Re
sistivity techniques and Ground Penetrating Radar
(GPR) were two of the electrical systems investigated
(Keller and Frischknecht, 1966). GPR appeared to have
the greatest possibility for use in the soil survey
(Morely, 1974). This new geophysical method permits,
by way of surface sensor, continuous real-time observa
tion and record of some soil properties below the
ground surface.
As a result of NASAs initial investigation, GPR
was further tested for use in soil survey in Florida
through a combined project of NASA, SCS, and
Technos, Inc. of Miami, Florida (Benson and Glaccum,
1979a).
MATERIALS AND METHODS
The system used in this work was the Geophysical
Survey Systems Inc. (GSSI) impulse radar, the only
system commercially available at the time of the study
(Benson, 1978).3 The GSSI unit is an impulse radar
system which radiates repetitive electromagnetic pulses
at optional frequencies of 80 to 1000 MHz into the
-Trade names are used to provide specific information. Their
mention does not constitute endorsement by the Federal Govern
ment.
earth from an antenna coupled to the ground surface
(Fig. 1). The transmitted radar signals are reflected
from various interfaces (or discontinuities) within the
ground and picked up by the radar receiver. These re
flectors may be different soil horizons, soil/rock inter
faces, man-made objects, or other materials with con
trasting dielectric properties. Fortunately, these dielec
tric contrasts are usually related to many common
physical and chemical properties in the soil associated
with bedding, cementation (blow count), voids, frac
tures, faults, intrusions, and manmacle metallic and
noil-metallic structures (Benson and Glaccum, 1979b).
Organic matter, salt content, clay mineralogy, particle
size, and moisture content are some soil properties
affecting dielectric properties.
For presentation of data, GPR signals are processed
and displayed by a graphic recorder. As the antenna is
moved along the surface, the recorder produces a
picture-like graphic record along a traverse. This pro-
ceduces a continuous profile very similar to a cross
section found at a roadcut. The antenna can be towed
at speeds up to 8 km/hr for rapid exploratory work.
Detailed studies can be performed by hand towing the
antenna at very slow speed (1/2 km/lir) or by placing
the antenna in a static mode at specific locations.
The choice of antennas is an important considera
tion. Generally, the low frequency components propa
gate to the greatest depths. However, the higher fre
quency components produce better resolution and thus
discriminate between closely spaced interfaces and ob
jects. Hence, the systems ability to use antennas with
a wide range of frequencies is important to meet vari
ous soil conditions with different attenuation coef
ficients or specific resolution requirements.
The GPR signals commonly penetrate to depths of
3 to 10 m, but penetrations as deep as 20 m have been
achieved under ideal conditions at some sites. The
depth of the penetration is related to the kind of soil
and its water content. For example, the depth of pene
tration is reduced if the soil is saturated with water, or
has an appreciable amount of silt or clay, and soils with
high montmorillonitic clays are highly attenuative of
the radar pulse and penetration may not exceed 1 m
Fig. 1.Simplified block diagram of the GSSI-GPR system.


70
Soil and Crop Science Society of Florida
(Benson, 1978). Similarly, radar is ineffective in soils
high in salts. However, water saturated soils which
have low conductivity may respond well to GPR.
Ground penetrating radar signal structure and the
resulting profile (Fig. 2) consist of three basic com
ponents. At the top of Fig. 2-a is the transmitted pulse,
or, more precisely, feed-through of the transmitted
pulse into the receiver section that serves as a time
reference. A strong surface reflection immediately fol
lows the transmitted pluse; then, at the time equal to
the pulse travel time from the surface to an interface
and back to the antenna, the interface reflection ap
pears.
The continuous stream of received pulses is fed into
the graphic recorder and a profile (Fig. 2-b) is devel
oped as the antenna is towed along the ground. The
graphic recorder produces an image by printing strong
signals (amplitudes beyond print threshold) as black
and weak signals with less intensity. Intermediate sig
nals, such as the noise on the profile between the sur
face and interface reflections, are in the gray range.
The profile is developed as the chart paper moves
under the graphic recorder stylus and sequential pulses
are printed to form a continuous record.
The main feature of the data is the display of dark
bands that extend throughout the profile at varying
detphs. These dark bands are displayed in groups of
three closely related bands. Each of these three banded
lines is the reflection from a single interface between
two materials. The triple band is a characteristic of
the radar system and is caused by oscillations in the
reflection of the pulse.
The vertical scale is initially time-scaled with the
travel time of the pulse. This travel time may be con
verted into a depth scale, if the velocity of propagation
in the particular material being surveyed is known.
Depth is calculated by the following relationship:
n = ct = ^
2\/e7 2
DEPTH
OR
TIME
a) SKETCH OF A SINGLE b) EXAMPLE OF PROFILE INFORMATION
PULSE AND REFLECTIONS AS DISPLAYED BY THE GRAPHIC
AS SEEN BY THE RECEIVER RECORDER
Fig. 2.Example of GPR single pulse and resulling graphic
presentation.
D = depth in meters
c = velocity of light = 3 x 10s m/sec
t = pidse travel time in nanoseconds
er = relative dielectric constant of material
vm = velocity of propagation in material = c
Ve r
Conductivity of the earth materials being probed
and the VHF frequency range dielectric constant de
termine the electromagnetic propagation velocity
(depth calibration) and propagation loss (penetration
depths) of the GPR system.
To calibrate the GPR data, either the dielectric
constant or the depth to a particular interface must be
known. The conductivities and dielectric constants of
various materials are presented in Table 1.
Table 2 lists various materials and their impulse
rate in nanoseconds per meter two-way travel time.
This shows the approximate time that is required for
a radar impulse to penetrate the material and be re
flected back to the antenna.
The horizontal scale is dependent upon the speed
TABLE 1.Conductivities and dielectric constants of selected
MATERIALS.
Material
Approximate
electrical
conductivity
it (mho/m)
Approximate
dielectric
constant, er
Air
0
1
Fresh Water
10-4 to 3 X 10-2
81
Sea Water
4 to 5
81 to 88
Fresh Water Ice
10-4 to 10-2
4
Sea Water Ice
10-2 to 10-1
4 to 8
Ice (Glacial)
10~6 to 10-4
3.2
Permafrost
10-5 to 10-2
4 to 5
Snow Firn
106 to 105
1.4
Granite
10-9 to 10-3
8
Sand, Dry
Sand, Saturated
10-1 to 10-3
4 to 6
(Fresh Water)
Silt, Saturated
10-4 to 10-2
30
(Fresh Water)
Clay, Saturated
10-3 to 10-2
10
(Fresh Water)
Average soil
10-1 to 1
8 to 12
10-4 to 10-2
16
TABLE 2.Approximate impulse rates for various
TERIALS (TWO-WAY TRAVEL TIME).
EARTH MA-
Impulse
Rate
Material
(ns/ft)
(ns/m)
Air
2
0.61
Fresh Water
18
5.5
Sea Water
18 to 19
S.5-5.8
Fresh Water Ice
4
1.2
Sea Water Ice
4 to 5.7
1.2-1.7
Ice (Glacial)
3.6
1.1
Permafrost
4 to 4.5
1.2-1.4
Snow Firn
2.4
0.7
Granite
5.7
1.7
Sand, Dry
4 to 4.9
1.2-1.5
Sand, Saturated
10.9
3.3
(Fresh Water)
Silt, Saturated
6.4
2.0
(Fresh Water)
Clay, Saturated
5.7 to 7
1.7-2.1
(Fresh Water)
Average soil
7 to 9
2.1-2.7


Proceedings, Volume 39, 1980
of the antenna as it crosses the ground and the paper-
feed rate of the graphic recorder. At a sample rate of
approximately 25 samples/sec, this results in a hori
zontal spatial scale of:
90 samples/m @ 1 km/hr
45 samples/m @ 2 km/hr
22.5 samples/m @ 4 kg/hr
The Soil Conservation Service selected one site for
study in Polk County and one in Hardee County,
Florida. Each site had an order 2 soil survey and con
tained a variety of soils. Table 3 shows the classifica
tion of the soils. Approximately 3.7 km of transects
were laid out for study in Polk County and 9.2 km in
Hardee County. Stakes, consecutively numbered, were
placed at approximately 30 m intervals along the line
of the proposed transect. Each station was marked and
keyed on tire graphic recorder as the antenna passed
the station. Ground truth was provided by making
auger observations at each station along the radar
traverse which passed approximately 1.5 m to the side
of tire station markers.
Both sites were traversed with low frequency (300
MHz) and high frequency (900 MHz) antennas. In
addition to the graphic presentation, data were re
corded on magnetic tape at 95.25 mm per second re
cording speed. The antenna was towed by a four-wheel
drive vehicle at a speed of 4.0 to 5.6 km/lrr. A sample
rate of 25.6 samples per second was used, resulting in a
minimum spatial sampling of approximately 20 sam
ples per linear meter or about 6 samples per linear foot.
RESULTS AND DISCUSSION
A review of tbe soil maps, topographic sheets, soil
boring logs, and the GPR records verified obvious soil
boundaries.
Detailed interpretation of data was accomplished
by reviewing soil boring and GPR records over a lim
ited number of stations. Relationships were first estab
lished between obvious subsurface horizons with lateral
continuity and GPR data so that more subtle differ-
TABLE 3.Taxonomic classification of soils investigated.
Soil Series
Classification (Subgroup)
Adamsville
Aquic Quartzipsaraments
Basinger
Spodic Psammaquents
Candler
Typic Quartzipsamments
Cassia
Typic Haplohumods
Delray
Grossarenic Argiaquolls
EauGallie
Alfic Haplaquods
Electra
Arenic Ultic Haplohumods
Felda
Arenic Ochraqualfs
Hontoon
Typic Medisaprists
Jonathan
Typic Haplohumods
Lawnwood
Aerie Haplaquods
Lochloosa
Aquic Arenic Paleudults
Myakka
Aerie Haplaquods
Oldsmar
Alfic Arenic Haplaquods
Ona
Typic Haplaquods
Pineda
Arenic Glossaqualfs
Pomello
Arenic Haplahumods
Pomona
Ultic Haplaquods
Samsula
Terric Medisaprists
Smyrna
Aerie Haplaquods
Sparr
Grossarenic Paleudults
Tavares
Typic Quartzipsamments
Tomoka
Terric Medisaprists
Wauchula
Ultic Haplaquods
71
enees between soil horizons could be more easily evalu
ated.
The soil surface was taken as the first crossover in
the primary return. Subsequent horizons were also
picked at the first crossover to provide an obvious
point in the response. The horizon picked at first cross
over was merely one of providing convenience and re
peatability in the interpretation procedure, but re
sulted in a depth somewhat greater than the actual
depth. However, this error was quite small, and the
repeatability in picking horizons was improved sub
stantially.
Generally, the GPR precisely identified key diag
nostic soil horizons. The GPR record substantiated
many delineations on the soil map, whereas in some
places it showed where more precise boundaries could
be placed. Map unit composition could be readily
calculated from these data; however, GPR did not
record all the subtle changes noted in the soil boring
logs, such as a slight increase or decrease in texture
(sandy loam to sandy clay loam). Most typically,
changes from albic horizons to spoclic and argillic
horizons were detected. This study did not attempt to
establish the capability of GPR to determine micro
aspects of soil horizons such as details very near the
surface; however, this might be accomplished by proper
windowing of the incoming radar signals and use of
a high frequency antenna.
In areas where the radar record showed an irregular
subsurface horizon, correlation with auger borings did
not always agree, most likely due to discrepancies be
tween the exact auger site and the radar track. Along
more uniform horizons, correlation of radar and auger
borings was as good as 2.5 to 5.0 cm.
Water tables are not usually detected by GPR be
cause in many soils the upper edge of the water table
is a capillary fringe rather than a discrete interface.
However, GPR appears to have detected the water
table in a few coarse textured soils in Hardee County.
Other studies in areas with coarse sandy and gravelly
soils detected a water table as deep as 6 m (Benson and
Glaccum, 1979a).
The 300 MHz antenna provided excellent data in
both areas, but the 900 MHz antenna was much less
effective. At least the 300 MHz antenna is probably the
best off the shelf antenna available for soil work. How
ever, properties of the upper 38 cm of soil are not de
tected by this antenna, because the first strong surface
reflection masked any changes in that part of the soil.
A better antenna may require a higher frequency to
minimize this dead zone. In addition, a change of
antenna frequency can be used to advantage in solving
many specific site problems, and it is unlikely that a
single antenna or frequency will effectively solve all
problems. Since the GSSI system is modular, it accepts
a wide range of antennas of various characteristics.
Custom designed antennas can be made for special ap
plications at a relatively low cost.
CONCLUSIONS
Ground penetrating radar provides a means of ob
taining a large quantity of detailed soil data in a rela
tively short time. It can also confirm the lateral con
tinuity of the soil horizons. Certain soil horizons will
provide characteristic target signatures. These signa
tures (Fig. 3) can often be readily followed throughout


72
Soil and Crop Science Society of Florida
Fig. 3.Radar profile record of an Argillic Horizon (Grossarenic Paleudult).
a profile. However, borings are needed to establish
ground truth for these signatures. Once correlation
and the interpreters skills have been developed at a
given area, lateral extension of information can be
made with a high degree of accuracy in most cases
without additional borings or certainly with a min
imum of borings.
Ground penetrating radar is capable of detecting
abrupt changes in depth to or in kinds of horizons that
may not be evident in the surface configuration of the
ground. In addition, it provides information about
minor changes in some soil properties as well as more
subtle transitions from one kind of soil to another.
Ground penetrating radar can be used as a recon
naissance tool to provide a graphic picture of changes
in subsurface soil properties. Then, locations can be
made for a limited number of borings for detailed
quantitative assessments.This approach economically
provides a maximum amount of data at a high level of
confidence, and labor-intensive soil boring is not
needed as the major exploration tool.
Present GPR technology permits definitive observa
tions to be made in many kinds of soils. However,
record quality varies depending on the many dielectric
soil properties discussed above. It is obvious that addi
tional work remains to define the complex range of
responses to site conditions as well as to specify the
limitations under which GPR is applicable. Advances
have been made in solving some of these problems
utilizing computer enhanced processing and filtering
techniques.
This study has demonstrated that GPR equipment
can be used to investigate soils to depths of at least
2 m. These may include both dry and wet soils as well
as soils under shallow fresh water.
Certain kinds of soil or site conditions cause poor
GPR performance. This may be due to high attenua
tion of the radar signal by the soil. A lack of contrast
(reflection coefficient) between the various earth ma
terials or soil layers can also account for the absence of
a radar response. However, at sites where penetration
and definition are obtained, GPR is highly useful in
site assessment or soil mapping.
LITERATURE CITED
1. Benson, R. 1978. Radar subsurface profiling. U. S. Army
Corps of Engineers, Waterways Experiment Station, Vicks
burg, MS. Technical Report.
2. Benson, R., and R. Glaccum. 1979a. The application of
ground penetrating radar to soil surveying. National Aero
nautics and Space Administration, Cape Kennedy Space
Center, FL. Technical Report.
3. Benson, R., and R. Glaccum. 1979b. Radar surveys for geo
technical site assessment. Geophysical Methods in Geotech
nical Engineering, American Society of Civil Engineers, At
lanta, GA.
4. Dobrin, M. D. 1960. Introduction to geophysical propecting,
2nd Edition. McGraw Hill.
5. Keller, G. V., and F. C. Frischknecht. 1966. Electrical methods
in general prospecting. Pergmen Press.
6. Morely, R. M. 1974. Continuous subsurfacing profiling by
impulse radar, American Society of Civil Engineers, Proceed
ings of Engineering Foundation Conference on Subsurface
exploration for underground excavations and heavy construc
tion, Hinniker, N. H.
7. Morey, R., P. Annan, J. Davis, and J. Rossiter. 1978. Impulse
radarprinciples and application, Course NotesVol. I and
II. Center for Cold Ocean Resources Engineering, Memorial
Un. of New Foundland, St. Johns, New Foundland.


Proceedings, Volume 39, 1980
73
Soil Characteristics and Their Relationship to
Growth of Needlerush1
Charles L. Coultas and Orion J. Weber2
ABSTRACT
Needlerush (Juncus roemerianus Scheele) is the
principal flowering plant in the tidal marshes of Flor
ida. Variability in needlerush production has been ob
served at different elevations within the marsh. This
study was undertaken in order to investigate some soil
and plant factors that may affect growth of needlerush.
Standing crop of needlerush was found to be higher
in low and middle marsh locations than in a high
marsh site which was above the level of daily tidal
inundation. Soils at lower elevations were higher in
N, organic C, and extractable cations and were more
reduced, warmer, and more moist than in the high
marsh. Regression analysis indicated a positive effect of
temperature and negative effect of pH on above ground
standing crop. Conductivity was positively correlated
with below ground biomass while surface soil tempera
ture was negatively correlated.
The possibility of genetic differences between plants
in high marsh and those in middle and low marsh was
investigated. There were gross morphological differ
ences between plants in high marsh and those in middle
and low marsh. Plants in low and middle marsh were
taller, thicker in diameter, and had fewer leaves per
unit area than those in a high marsh position. Trans
planting plants from high to low marsh and vice-versa
did not affect original differences in height and diam
eter. High marsh plants transplanted to low marsh
survived poorly, however, indicating their poor adapta
tion to this reduced environment.
Additional Index Words: Tidal marshes, Biomass,
Haplaquods, Haplaquents.
There are approximately 303,750 ha (750,000 acres)
of tidal marsh in Florida (U.S. Dept. Interior, 1954).
Tidal marshes are productive ecosystems because of
abundant nutrients supplied by tidal action (Schleske
and Odum, 1961; Odum, 1971). Marsh plants in the
northwest coast of Florida are predominantly needle
rush (Juncus roemerianus Scheele). Kruczynski et al.
(1978) found that net aerial production of needlerush
decreased landward from 949 g/m2/year in low marsh
to 243 g/m2/yr in high marsh in the same north Florida
marsh as the present study. Average live standing crop
was 728, 548, and 255 g/m2 in low marsh, middle
marsh, and high marsh, respectively. In another study,
Kruczynski et al. (1978) found that protein content of
needlerush shoots ranged from 5.7 to 6.4% with no
significant difference among marsh zones. Total P was
0.04% in all zones.
Application of 200 kg N/ha as ammonium nitrate
to short and tall Spartina alterniflora Loisel and
needlerush in a Georgia marsh resulted in increased
biomass production with short S. alterniflora but not
with the tall form or needlerush (Gallagher, 1975).
iThis research was supported by a research program (FLAX
79006) from SEA/CR, USDA.
2Professor and Laboratory Technician, Florida A & M Uni
versity, Tallahassee, FL 32307.
No differences were noted in the N content of needle
rush foliage due to fertilization. Three levels of N and
P were applied to an undisturbed mid-marsh zone of
needlerush in north Florida (Luce, H. D., and C. L.
Coultas. 1976. Effect on N and P fertilization on the
growth, N content, and P content of a natural stand of
Juncus roemerianus near St. Marks, Florida. Agronomy
Abstracts, Am. Soc. Agron. Madison, Wis. p. 149-150).
No increase in biomass resulted from any treatment,
but higher concentration of N was found in foliage
after N fertilization.
Diverse soils have been found in the tidal marshes
of Florida (Coultas, 1969, 1970; Coultas and Gross,
1975; Coultas and Calhoun, 1976, and Coultas and
Gross, 1978). These soils are saline, poorly drained, and
tend to be higher in organic matter, clay, and extracta
ble bases than associated upland soils.
The purpose of this research was to study the re
lationship of several soil characteristics to the growth
of needlerush and to investigate the possibility of
genetic variability. This information should provide
more tools for improved management of this ecosys
tem.
METHODS AND MATERIALS
In October 1977, 12 square meter plots were laid
out in low marsh, mid-marsh, and high marsh zones
in a tidal marsh of needlerush near St. Marks Light
house in north Florida. The location of these plots
was shown in Kruczynski et al. (1978). Low marsh
plots were 0.7 to 1.0 m, mid-marsh plots were 1.0 to
1.2 m, and high marsh plots were 1.2 to 1.6 m above
mean low water. Plots were replicated once in each
zone. Soils were classified as Haplaquods in high and
middle marsh and Haplaquents in low marsh. At
monthly intervals for 12 months the following plant
measurements were made: total standing crop (live
and dead), total root biomass, and total rhizome bio
mass in a core 25 x 25 cm by 8 cm. Plant samples were
oven-dried at 80 C and weighed. Monthly soil measure
ments were made as follows: redox at 2, 8, and 15 cm
with an Orion ionalyzer with Pt electrodes; soil tem
peratures at 2, 8, and 15 cm with mercury thermom
eters; conductivity of soil extract (Jackson, 1958); K
in soil solution with an atomic absorption spectro
photometer; pH on the saturated paste with glass
electrodes; and soil moisture gravimetrically. Previous
to the experiment soils were characterized in each zone:
pFI (Jackson, 1958), total N (Bremner, 1965), organic
C (Jackson, 1958), extractable cations and cation ex
change capacity (CEC) (Jackson, 1958, and particle
size analysis (Day, 1965). Total N was determined on
the soil extract by the Kjeldahl procedure (Jackson,
1958) with DeVardas alloy. Total P in the extract was
determined by the ammonium molybdate method
(Jackson, 1958) in a Beckman DU spectrophotometer
at 900 mu.
Net production was determined by the monthly
change in biomass method (Smalley, 1959; Teal, 1962).
Data were analyzed by analysis of variance, regression


74
Soil and Crop Science Society of Florida
analysis, and Duncans Multiple Range Test as ap
propriate.
In July 1978 a transplanting study was begun.
Cores of soil measuring 20 cm in diameter and 13 cm
in thickness and containing established needlerush
were employed. Eight cores from the high marsh were
transplanted to the low marsh and 8 cores from the low
marsh were moved to the high marsh. In addition, 8
cores in both high and low marsh were replanted in the
same elevational zone. Three measurements were made
at monthly intervals for 1 year and after 21 months:
number of leaves, diameter of leaf, and height of leaf.
RESULTS AND DISCUSSION
Table 1 establishes that the low marsh soils were
highest in N, organic C, CEC, silt + clay, and ex
tractable bases. High marsh soils were lowest in these
measurements. Mean monthly standing crop of shoots
was highest in low marsh (515 g/m2), lowest in high
marsh (343 g/m2), and intermediate in middle marsh
(413 g/m2) as seen in Table 2. There were significant
differences among months with the highest yield in
July and the lowest in March. Monthly root and
rhizome biomass weights are presented in Table 3.
Average yields in low and middle marsh were 13.7 and
14.6 mg/cm3, respectively, and 7.4 mg/cm3 in high
marsh. There was a significant effect of month on root
yields with highest average yields occurring in October
and lowest in March.
Determination of production by the monthly
change in biomass resulted in no significant difference
among the marsh zones with either standing above
ground crop or below ground biomass. Net monthly
production of shoots was 156 g/m2 for low marsh, 77
g/m2 for middle marsh, and 185 g/m2 for high marsh.
Net production of roots was 1.78 mg/cm3 for low
marsh, 2.21 mg/cm3 for middle marsh, and 1.14
mg/cm3 for high marsh. This was not in agreement
with the work of Kruczynski et al. (1978) nor with the
standing crop data in this study. No apparent rela
tionship occurred between net production calculated
in this manner and soil measurements. For these
reasons we will assume that standing crop data is a
fair estimation of production in the remainder of our
discussion.
There were significant differences among the marsh
zones and months with most of the soil measurements
observed (Fig. 1, 2). Mean annual redox potential at
15 cm was lower in the low and middle marsh, 178
and 128 mv, respectively, than in the high marsh
where it was +357 mv. Conditions were most reduc
ing in August. Similar differences also occurred at the
2 and 8 cm soil depths and differences among all three
TABLE 2.Above ground standing crop of needlerush in three
MARSH ZONES, g/m2.
Month
Low
Marsh Zone
Middle
High
Mean
Oct.
503
390
412
435 ab
Nov.
455
361
299
371 b
Dec.
531
323
289
381 b
Jan.
476
343
259
361 b
Feb.
543
367
326
412 b
Mar.
517
334
254
358 b
April
569
391
289
417 b
May
467
485
300
418 b
June
500
542
400
481 ab
July
746
452
450
549 a
August
439
525
388
451 ab
Sept.
464
446
448
452 ab
Mean
515 a*
413 b
343 b
F values:
Marsh61.98;
Month4.18 (both sig.
at .05 level).
* Means with like letters are not significantly different at .05
level.
zones were significant with the low marsh soils the
most reduced. Mean annual temperatures at 2 cm
were different in all three zones with the middle marsh
being warmest (21.8 C) and the high marsh being cool
est (20.5 C). At 15 cm there was no difference between
the low marsh and middle marsh, but the low marsh
was warmer than the high marsh. February was the
coolest month with a mean at 15 cm of 6.8 C, and July
and August were the warmest with a temperature of
27.7 C.
There was no difference in conductivity of soil ex
tract among the marshes. The lowest conductivity,
TABLE 3 Below ground roots and rhizomes of needlerush in
THREE MARSH ZONES, mg/cmt
Marsh Zone
Month
Low
Middle
High
Mean
Oct.
25.8
15.3
12.9
16.8 a*
Nov.
18.6
20.9
7.6
15.7 ab
Dec.
18.4
19.5
6.2
14.7 ab
Jan.
10.4
17.4
8.5
12.1 ab
Feb.
13.6
20.9
8.0
14.2 ab
Mar.
7.8
10.2
5.9
8.0 b
April
12.6
12.4
7.1
10.7 ab
May
10.5
13.9
7.7
11.3 ab
June
11.0
11.3
6.2
9.5 ab
July
15.3
11.8
4.8
10.6 ab
Aug.
11.4
14.0
4.6
10.0 ab
Sept.
12.8
8.1
9.1
10.0 ab
Mean
13.7 ab*
14.6 a
7.4 b
F values:
Marsh8.95;
Month-3.17
(both sig.
at .05 level).
*Means with like letters are not significantly different at .05
level.
TABLE LSome physical and chemical characteristics of surface soils in three marsh zones.!-
Marsh
zone
Field
moist
pH
Sand
Silt
Clay
CEC
Ca
Extractable cations
Mg K
Na
Total
N
Organic
C
Conductance
.. %
%
mmhos/cm
Low
6.3
84
8
8
17.0
4.7
1.3
0.9
4.7
0.37
9.42
24.5
Middle
6.2
88
6
6
8.3
2.7
1.6
0.8
1.8
0.16
5.02
27.3
High
6.3
93
4
3
3.4
1.2
0.5
0.2
2.2
0.06
1.58
24.4
JData are the mean of 2 plots.


75
Proceedings, Volume 39, 1980
High marsh
Fig. 1.Monthly variations in soil redox potential in three
marsh zones at 15-cm depth.
Fig. 2.Monthly variations in soil temperature in three marsh
zones at 15-cm depth.
18.6 mmhos/cm, was recorded in April and the high
est, 38.0 mmhos/cm, in November. The low and
middle marsh soils were the most moist with 127 and
94% moisture, respectively, and the high marsh was
the driest containing only 30% moisture (Fig. 3).
There was no monthly difference in moisture within
marsh zones. With K there was no difference in con
centration among marsh zones, but K was highest in
Middle marsh
High marsh
Fig. 3.Monthly variations in soil moisture in three marsh
zones at 15-cm depth.
October (365 PPM) and lowest in April (228 PPM).
There was no effect of months on pH, but the middle
marsh was more acidic than the low and high marsh
(Fig. 4). The pH was 5.9 in the middle marsh and 6.2
in the low and high marshes.
The low marsh and middle marsh zones were the
most productive as indicated by standing crop. The
soils of these areas were the most reduced and warm
est, and contained the most moisture. There was a
significant negative correlation of redox on both above
ground and below ground biomass (Table 3). Soil
temperature had a positive relationship with above
ground crop but a negative effect on roots and
rhizomes. Conductivity, moisture, and K content were
positively correlated with both above and below
ground yields.
Correlation of significant soil measurements on
yield by marsh zone is presented in Table 5. There
was no significant correlation in the low marsh zone,
but soil temperature was positively correlated with
above ground standing crop in both the middle and
high marsh zones and negatively correlated with the
roots and rhizomes in the middle marsh. Conductivity
and K levels were positively correlated with shoot
yields in the high marsh.
We can conclude from Tables 5 and 6 that redox
differences within each marsh zone were not sufficient
to affect yields significantly. Temperature differences
did not affect yields in the low marsh, but did in the
Fig. 4.Monthly variations in soil pH in three marsh zones
at 15-cm depth.
TABLE 4.Correlation of certain soil measurements with
yield. All zones averaced.
Independent Variable
Soil
measurement
r valuef
Above ground standing crop
Redox 1, 2, 3*
-0.45 to -0.53
Temp. 1, 2, 3*
0.40 to 0.42
Conductivity
0.22
Moisture
0.46
K
0.26
Below ground biomass
Redox I, 2, 3
-0.22 to -0.49
Temp. 1, 2, 3
-0.22 to -0.29
Conductivity
0.39
Moisture
0.48
K
0.40
*1, 2, 3-2, 8, 15 cm depth,
fr values significant at 0.05 level.


76
Soil and Crop Science Society of Florida
TABLE 5.Correlation of certain soil measurements and
yield. Individual marsh zones.
Marsh
zone
Independent
variable
Soil
measurement
r valuef
Low
No significant effects
Middle
Above ground stand
ing crop
Below ground bio
mass
T 1, 2, 3*
T 1,2, 3
0.58 to 0.61
-0.53 to -0.56
High
Above ground stand-
inb crop
T 1, 2, 3
0.31 to 0.47
Conductivity
0.43
K
0.40
*1, 2, 3temperature at 2, 8, 15 cm depth,
tr values significant at 0.05 level.
middle and high marshes where temperatures were
probably more variable. Soil moisture variations within
zones were not sufficient to affect yields.
Oxidation-reduction status of the soil affects nu
merous soil properties (Phung and Fiskell, 1973;
Redman and Patrick, 1965). Available P would prob
ably be highest in the low and middle marsh zones
where conditions were most reducing. In a previous
study (Luce and Coultas, 1976), needlerush did not
respond to P fertilization in a middle marsh zone,
indicating the high availability of P in these soils. Soil
moisture certainly has an effect on redox, but it also
may be a limiting growth factor in the high marsh, but
not likely so in the middle or low marsh zones. Air
temperature is known to have a positive effect on
needlerush shoot growth (Kruczynski et ah, 1978;
Williams and Murdoch, 1972). This study confirmed
that soil temperature, which was highly correlated with
air temperature, was positively correlated with shoot
growth also. Potassium content had a positive rela
tionship with yield. This suggested that K was a
limiting element at least in the high marsh.
Higher conductivity results in greater stress on the
plant and expected yields would be lower. This study
did not support this contention, however.
Although soils of the low marsh were better sup
plied with total N than soils from middle or high
marsh, no difference in soil solution N was detected.
No difference was found in P content of soil solution,
either. From the protein data of Kruczynski et al.
(1978) it would have to be concluded that the soil pro-
TABLE 6.The affect of elevation on the growth of neddle-
rush 21 months after transplanting.
Treatment
Leaves
Leaf
height
Leaf
diameter
no.
cm
mm
H to Lf
9.3 a*
38.1 a
1.41 a
H to H
13.9 a
42.7 ab
1.43 a
L to H
15.8 a
56.5 be
2.28 b
L to I.
28.5 b
59.3 c
2.50 b
+H to L-
-high to low marsh, H
to Hhigh
to high marsh, L
to Hlow to high marsh, L to Llow to low marsh.
Like letters indicate no significant differences. Numbers are
treatment means.
vided more N and P in low and middle marsh zones
than in the high marsh zone. The higher levels of ex
tractable bases found in the lower zones could have had
some effect on yields.
The regression equation of yield in above ground
standing crop in low marsh is: y = 776 (174) + 6.54
(1.26) T3 60.69 (28.53) pH. The numbers in paren
theses are the standard errors. For middle and high
marsh zone yields, 122 and 173 should be subtracted,
respectively. For below ground biomass in the low and
A
middle marsh zone the equation is: y = 80.3 (14.0) +
2.08 (1.01) T3 + 0.71 (0.32) Conductivity 3.24 (1.04)
Tl. For high marsh subtract 32.2.
Another possible explanation for the differences
between yields of low and middle marshes vs high
marsh may be due to genetic differences. Needlerush
plants in the lower marsh tended to have taller, thicker,
and fewer leaves per unit area than those in high
marsh. Twenty one months after transplanting low
marsh plants to the high marsh they had taller and
thicker leaves than high marsh plants moved to the
low marsh (Table 6). Fewer leaves survived in the high
marsh cores moved to low marsh than with low marsh
replanted in low marsh. This suggested that the plants
from the high marsh were not adapted to the reducing
soil conditions that occurred in the low marsh. This
study further suggested that there were significant
genetic differences between needlerush at high marsh
elevations and that in low marsh. This, no doubt,
caused some of the differences between standing crop
found at different elevations.
LITERATURE CITED
1. Bremner, J. M. 1965. Total nitrogen. In C. A. Black (ed.).
Methods of soil analysis, Part 2. Agronomy 9:1149-1179. Am.
Soc. Agron., Madison, Wis.
2. Coultas, C. L. 1969. Some saline marsh soils in north Florida,
Part I. Soil Crop Sci. Soc. Florida. Proc. 29:111-123.
3. Coultas, C. L. 1970. Some saline marsh soils in north Florida,
Part II. Soil Crop Sci. Soc. Florida. Proc. 30:275-282.
4. Coultas, C. L., and E. R. Gross. 1975. Distribution and prop
erties of some tidal marsh soils of Apalachee Bay, Florida.
Soil Sci. Soc. Am. Proc. 39:914-919.
5. Coultas, C. L and F. G. Calhoun. 1976. Properties of some
tidal marsh soils of Florida. Soil Sci. Soc. Am. Proc. 40:72-76.
6. Coultas, C. L., and E. R. Gross. 1978. Tidal marsh soils of
Floridas middle Gulf Coast. Soil Crop Sci. Florida Proc. 37:
121-125.
7. Day, P. R. 1965. Particle fractionation and particle size
analysis. In C. A. Black (ed.). Methods of soil analysis, Part 1.
Agronomy 9:545-576. Am. Soc. Agron., Madison, Wis.
8. Gallagher, J. L. 1975. Effect of an ammonium nitrate pulse
on the growth and elemental composition of natural stands
of Spartina alterniflora and Juncus roemerianus. Am. J. Bot.
62(6):644-648.
9. Jackson, M. L. 1958. Soil chemical analysis. Prentice Hall,
Inc., Englewood Cliffs, N. J.
10. Kruczynski, W. L., C. B. Subrahmanyam, and S. H. Drake.
1978. Studies on the plant communities of a North Florida
salt marsh. Part 1. Primary production. Bull. Marine Sci. 28:
316-334.
11. Kruczynski, W. L and S. H. Drake. 1976. Studies on the
animal communities in two north Florida salt marshes. Part
2. Macroinvertebrate communities. Bull. Marine Sci. 26:172-
195.
12. Odum, E. P. 1971. Fundamentals of ecology, W. B. Saunders
Co., Philadelphia.
13. Phung, H. T and J. G. A. Fiskell. 1973. A review of redox
reactions in soils. Soil Crop Sci. Soc. Florida Proc. 32:141-145.
14. Redman, F. H., and W. H. Patrick, Jr. 1965. Effect of sub
mergence on several biological and chemical soil properties.
Louisiana State University Bull. 592. Baton Rouge.
15. Schelske, C. L., and E. P. Odum. 1961. Mechanisms main-


77
Proceedings, Volume 39, 1980
taining high productivity in Georgia estuaries. Proc. Gulf
Carib. Fish Inst. 14:75-80.
16. Smalley, A. E. 1959. The growth cycle of Spartina and its
relation to the insect population in the marsh. Proc. Salt
Marsh Conf. Sapelo Island, Ga.
17. Teal, J. M. 1962. Energy flow in the salt marsh ecosystem of
Georgia. Ecology 43:614-624.
18. U.S. Dept, of Interior. 1954. The wetlands of Florida in rela
tion to their wildlife value. River Basin Studies Staff, Fish
and Wildlife Service. Atlanta, Ga.
19. Williams, R. B., and M. B. Murdoch. 1969. The potential
importance of Spartina alterniflora in conveying zinc, man
ganese, and iron into estuarine food chains. Proc. Second Nat.
Symp. Radioecol. 431-439.


78
Soil and Crop Science Society of Florida
CROPS SECTION
Effect of Metalaxyl Fungicide (CGA 48988) on Blue Mold
and Black Shank of Tobacco1
Tom Kucharek, E. B. Whitty and John Taylor2
ABSTRACT
Metalaxyl fungicide dramatically reduced black
shank and blue mold of tobacco with a single preplant
incorporated treatment. Black shank assessments were
made near harvest time and blue mold assessments
were made 53 to 60 days after transplanting. The high
degree of control of both diseases for such a long period
of time suggests that metalaxyl may offer new options
in control strategies for tobacco diseases.
Additional Index Words: Nicotiana Tobacum,
Phytophthora Parasitica var Nicotiane, Peronospora
Tabacina.
Black shank of tobacco (Nicotiana tabacum L.),
caused by the fungus Phytophthora parasitica (Dast.)
var nicotiane (Breda de Hann) Tucker, has been a
serious disease of flue cured tobacco in Florida since
1961 (7). Black shank causes lower yields where suscep
tible varieties are used or compels growers to use re
sistant cultivis that may not possess buyer appeal. To
further complicate the problem, cultivars with mod
erate to high resistance to black shank have been in
fected recently to a higher degree than expected. Often
growers have short crop rotations due to installation
of centrally located irrigation systems, land availability
or land rental costs. Such situations contribute to
higher inoculum levels in production fields thereby
lowering the effectiveness of incomplete resistance.
Thus the use of an effective, economical chemical
would be beneficial for the control of black shank.
Kannwisher and Mitchell (4) found in Florida that
metalaxyl (N-(2,6-diamethylphenyl)-N-(methotyacetyl)
alanine methyl ester) was effective when this fungicide
was used in conjunction with a cultivar, Speight G-28,
that possesses moderate to high resistance to black
shank. Young et al. (9) found metalaxyl to be highly
effective against black shank when used in transplant
water or preplant incorporated treatments in field tests.
Metalaxyl fungicide, besides being effective against
Phytophthora spp., is effective also against other
oomycete fungi, some of which are pathogens of to
bacco in Florida (2, 3, 8, 9). Pythium spp. cause root
and stem rots of plants in the transplant beds in most
years. In some situations the problem is quite severe,
causing the grower to either transplant weak plants or
search for an alternative source of plants. Peronospora
tabacina Adam., the causal agent of blue mold, has not
been the problem in recent years in the transplant bed
as it was in past years (5, 6). However, in 1979 an
epidemic of blue mold occurred in the field from
^Florida Agricultural Experiment Stations Journal Series No.
2005.
Associate Professor, Plant Pathology Department, University
of Florida, Gainesville 32611, and Professor, Agronomy Depart
ment, University of Florida, Gainesville 32611, and Research
Representative, Ciba Geigy Chemical Company, 1032 North
Boulevard, Deland, Florida 32720.
Florida to Canada. Metalaxyl has been found to be
effective against both Pythium spp. and Peronospora
sp. (9). Johnson et al. (3), in Austraila, found trans
plant water, soil drench, and spray treatments of
metalaxyl to be effective in controlling blue mold.
The purpose of this test was to determine if a single
preplant incorporated treatment of matalaxyl would
offer effective, season long control of black shank on
tobacco. Because of the unexpected epidemic of blue
mold in the tests, efficacy data were gathered also on
the effect of metalaxyl on blue mold.
MATERIALS AND METHODS
The fungicide metalaxyl, formulated as a 2EC, was
used in all tests in comparison with untreated controls.
Metalaxyl was applied at a rate of 2.24 Kg. a.i. per
hectare in a broadcast manner. Applications were pre
plant incorporated with rotary harrows to a depth of
5 to 10 cm. Applications were made from one to two
days prior to transplanting. Water rates used to dis
perse the fungicide varied from 374 to 468 liters/ha
between tests. All applications were made using flat
fan nozzles. Tests were conducted on four farms in
Florida. Transplanting was done on April 6, 1979 for
the Busick test, April 10 for the Fraliegh test, April 12
for the Lites test, and April 14 for the Lindsey test.
The cultivar Speight G-28, possessing moderate
to high resistance to black shank, was used in all tests.
Black shank assessments were made when plants were
in growth stage 7 to 8 (1). Specifically, assessments
were made 102, 96, and 94 days after transplanting for
the Busick, Lites, and Lindsey tests, respectively. No
black shank assessments were made for the Fraliegh
test as no significant amount of black shank occurred
in this test area. Three subsamples of two rows, each
153 m in length, were used in all tests to count black
shank infected plants in both treatments. For statistical
comparisons, each of three farms is considered as a
block as treatments were not replicated on individual
farm tests.
Blue mold assessments were made by counting the
total number of lesions on every tenth plant in the row.
Blue mold lesions were classified as uninterrupted and
interrupted. Interrupted lesions are those without
sporulation and uninterrupted lesions are those where
sporulation occurred. Specifically, assessments were
made 56, 60, 57 and 53 days after transplanting for the
Busick, Fraleigh, Lites and Lindsy tests, respectively.
Assessments were made when plants were in growth
stages 6-7.
RESULTS
Severe black shank epidemics occurred in the
Busick and Lindsey tests and in the Lites test a light
epidemic occurred. Only a few scattered black shank
infected plants occurred in the Fraleigh test and there
fore no differential effects between metalaxyl and the


79
Proceedings, Volume 39, 1980
control could be discerned in this test. The differential
effect between metalaxyl and the control was spectac
ular in the three other tests (Table 1). Metalaxyl re
duced the percent of infected plants front 35.9 to 0.1,
1.4 to .07, and 34.9 to 2.7 in the Busick, Lites and
Lindsey tests, respectively. It is noteworthy that this
high degree of control was measured at or near harvest
time with a single preplant incorporated application.
Blue mold epidemics occurred in all four tests. Al
though we observed other tobacco fields in Florida with
more severe epidemics of blue mold, substantial differ
ential effects occurred between metalaxyl treatments
and controls (Table 2). These data were collected near
the peak for each epidemic. Metalaxyl reduced spor-
ulating lesions by no less than 99 percent in all tests.
Within the metalaxyl treatments some lesions occurred
that were typical of blue mold on the upper leaf surface
but lacked sporulation on the under leaf surface. Such
lesions are referred to as being interrupted. The fre
quency of interrupted lesions was slightly higher than
uninterrupted lesions, but if a comparison is made
between uninterrupted lesions in the controls to inter
rupted lesions in metalaxyl treatments all reductions
exceeded 86 percent.
DISCUSSION
The degree of control of tobacco black shank and
blue mold was outstanding with metalaxyl as a single
preplant incorporated treatment. Such a practice in
commercial fields could offset some current concerns
in relation to higher inoculum levels of P. parasitica
var. nicotiana where crop rotation can not be utilized.
Also, growers might benefit further where they grow
TABLE 1.Efficacy of metalaxyl fungicide against black
SHANK OF TOBACCO, CULTIVAR SIEIGHT G-28.
Farm
Days Afterf
Transplanting
No. of diseased plants/
300 m. of row
Metalaxyl
Untreated 2.24 Kg./ha
Control (ppi)
Busick
102
269.0
1.0
Lites
96
10.3
0.7
Lindsey
94
261.7
20.3
JPIants were in growth stage 7-8.
TABLE 2.-
-Efficacy of metalaxyl fungicide against blue mold
OF TOBACCO, CULTIVAR SPEIGHT G-28.
Number of lesions per
30 plantsf
Metalaxyl
Days After*
Untreated
2.24 Kg./ha
Farm
Transplanting
Control
(PP1)
U§ _I_
U I
Busick
56
156 0
0 14
Fraleigh
60
1470 0
4 13
Lites
57
36 0
0 5
Lindsey
53
432 0
0 2
fTotal number of lesions were counted on every tenth plant
in each of three rows in the Busick and Lindsey farms and in
each of two rows on the Lites and Lindsey farms.
+A11 plants were in growth stages 6-7.
§U = uninterrupted, sporulating lesions. I interupted,
with no sporulation.
cultivars that have more buyer appeal rather than
where they grow a variety that is resistant to black
shank. A fungicide such as metalaxyl offers a further
advantage in that the systemic movement of this prod
uct is less apt to vary in efficacy compared to preplant
multipurpose fumigants where soil type, temperature,
and moisture heavily influence efficacy. Also, land that
is fumigated in the row is commonly reinfestecl by the
pathogen from non-fumigated areas between rows by
irrigation with contaminated pond water, or by move
ment of field equipment. A fungicide such as metalaxyl
could offset these problems as well.
Further studies on the effect of broadcast preplant
incorporated metalaxyl in combination with black
shank susceptible cultivars should offer definitive in
formation on whether the grower can achieve com
mercial control with such a combination. Kannwischer
and Mitchell (4) found that metalaxyl as a transplant
water treatment began to lose efficacy near 50 days
after transplanting when used on Hicks, a susceptible
cultivar, whereas metalaxyl combined with Speight
G-28, a moderately resistant cultivar, afforded ex
cellent control beyond 90 days after transplanting.
The blue mold epidemic in 1979 was the first such
epidemic known to occur in flue-cured tobacco fields
in Florida. Yield losses up to ten percent have been
estimated for some fields. State-wide losses are not ex
pected to exceed two percent. At the time of this writ
ing 30 percent yield losses or more are estimated for
Burley tobacco fields in North Carolina (Furney Todd,
personnel communication). Blue mold was effectively
controlled in these studies by metalaxyl. Although blue
mold is not expected to be severe in most years,
metalaxyl has an additional attribute if a potential
epidemic is thwarted.
Metalaxyl apparently has curative effects (2.9) and
this may explain in part the presence of blue mold
lesions without sporulation. Data presented herein and
elsewhere (2, 3, 4, 8, 9) suggest that metalaxyl, besides
being a new chemistry for a disease control agent, also
possesses desirable characteristics such as high degrees
of efficacy, longevity of efficacy and no noticeable phyto
toxicity. Such attributes offer flexibility in plant disease
control strategies.
LITERATURE CITED
1. Chiarappa, L. 1971. Crop loss assessment Methods: FAO
Manual on the evaluation and prevention of losses by pests,
disease and weeds. F.A.O. Organization of the United Nation
and Commonwealth Agricultural Bureaux. Miscellaneous:
4.4.4/1.
2. Cohen, Y., M. Reuveni, and H. Eyal. 1979. The systemic
antifungal activity of Ridomil against Phytophthora in
festaos on tomato plants. Phytopathology. 69:645-649.
3. Johnson, G. I., R. D. Davis, and R. G. OBrien. 1979. Soil
application of CGA 48988a systemic fungicide controlling
Peronospora tabacina on tobacco. Plant Disease Reporter
63:212-215.
4. Kannwisher, M. E., and D. J. Mitchell. 1978. The influence
of a fungicide on the epidemiology of black shank of tobacco.
Phytopathology 68:1760-1765.
5. Kincaid, R. R., and W. B. Tisdale. 1939. Downy mildew
(blue mold) of tobacco. University of Florida, Bull. 330. 28 pp.
6. Lucas, G. B. 1975. Diseases of tobacco. Biological Consulting
associates, Raleigh, North Carolina. 621 pp.
7. Miller, C. R. 1966. Characterization of the causal organism
of tobacco black shank of Florida flue-cured tobacco: pre
liminary report. Soil and Crop Science Society of Florida.
26:189-193.
8. Tsakiridis, J. P., Ch. B. Varilakakis, and A. P. Chrisochou.
1979. Evaluation of new systemics and nob-systemic fungicides


80
Soil and Crop Science Society of Florida
for the control of Peronospora tabacina in tobacco seedbeds Acylalanines: A new class of systemic fungicides. Proc. Fia.
and fields in Greece. Plant Disease Reporter. 63.63-66. State Hort. Soc. 90:327-329.
9. Young, T. R., E. B. Seifried, and W. L. Biehn. 1977.
Legume Covercrop Trials in Citrus Groves1
Carl A. Anderson2
ABSTRACT
Three field experiments were conducted to com
pare dry matter production and N content of various
legumes that might be used as covercrops in citrus
groves. One test was in a young replanted grove on
excessively-drained sandy soil in central Florida. The
site had been in citrus for over 50 years. Eight legumes
were tested: hairy indigo (Indigofera hirsuta L.),
Aeschynomene (A. americana L.), Stylosanthes (S.
hamata taub. cv. Verano), alyceclover (Alysicarpus
vaginalis L.), cowpeas (Vigna sinensis L.), pigeonpea
(Cajanus cajan L. Mill sp.), and two soybeans (Glycine
max cv. Hardee and Jupiter). All seeds were inoculated
with N-fixing bacteria before seeding and no N fer
tilizer was used during the test. Only a few of the
legumes seeded in March survived infestations of ring
and sting nematodes. The most productive crop was
hairy indigo which produced 10.4 tons dry matter/ha,
containing 1.6% N. Stylosanthes and Aeschynomene
produced approximately 5 tons/ha. All eight legumes
were destroyed by lesser corn stalk borer when seeded
in June. In another test on similar but previously un
planted sandy soil, dry matter yields of approximately
6 tons/ha were obtained from March seedings of
pigeonpea, alyceclover, and Aeschynomene. In a test
in a bedded grove on poorly-drained, fine-textured soil
on the east coast, both pigeonpea and Crotalaria (C.
mucronata Desv.) produced approximately 10 tons
dry matter/ha. Hairy indigo and Aeschynomene pro
duced almost 7 tons/ha. Some of the crops seeded in
March were damaged by rodents and insects.
Additional Index Words: Biological nitrogen fixa
tion, Plant analysis.
Nitrogen fertilization of citrus is one of the most
expensive grove practices in Florida, in terms of energy
consumption. It will remain expensive as long as fossil
fuels continue to be used as raw materials and as energy
sources in the manufacturing process of nitrogen fer
tilizers. A reduction in N usage on citrus cannot be
expected because fruit yield and application rate are
closely related up to a maximum of about 225 kg
N/ha/year and very few bearing groves are presently
receiving more than that amount. Although the rate
of N application is an important factor in citrus pro
duction, verified by numerous N source and rate ex
periments listed elsewhere (2), the source of N is not
generally important. Many legumes are capable of
iFlorida Agricultural Experiment Stations Journal Series No.
1978.
a.Associate Professor, University of Florida, Institute of Food
and Agricultural Sciences, Agricultural Research and Education
Center, Lake Alfred, Florida 33850.
fixing between 100 and 200 kg N/ha/year (4). For
these reasons a study of legume covercrops in citrus
groves to provide biologically-fixed N is feasible.
The establishment of legume covercrops in groves
could be expected to provide other benefits to citrus in
addition and unrelated to that of N nutrition. Good
stands of legumes might help replenish the supply of
organic matter (O.M.) in soils. O.M. content and
cation exchange capacity (C.E.C.) have been strongly
correlated for sandy soils in groves in central Florida
(Fig. 1). Any practice that increases the C.E.C. might
increase the efficiency of use of K and Mg fertilizers as
well as reduce the toxicity of Cu which has accumu
lated to high levels in some grove soils. Increasing the
O.M. content might improve various water related
properties of soil. Finally, the low O.M. content of
Fig. 1.Correlation of cation exchange capacity and organic
matter content of surface soils from 42 citrus groves on the Ridge.
Data of Anderson and Albrigo (1).


Proceedings, Volume 39, 1980
soils has been indicated as being a factor in the inci
dence of citrus tree blight (5).
Traditionally, citrus groves on the sand hills in
central Florida are clean-cultivated twice each year,
just before harvest to facilitate picking operations and
again in the late fall to enhance cold protection. This
latter cultivation, generally carried out in October, is
considered to be of extreme importance for all groves
regardless of age or variety. The most suitable cover-
crops, therefore, would be annual legumes that could
attain maximum forage production and N fixation
and, preferably, complete seed development prior to
the fall cultivation. Ideally, the seed produced one
year would reestablish the crop the following year.
In most flatwood groves, grass sod is maintained
throughout the year to protect the beds and furrows
from soil erosion. Annual legumes seeded in the spring
would give maximum cover during the late summer
and fall, the period of heaviest rainfall.
The objective of this study was to compare dry
matter production and N content of several annual
legumes grown on soils commonly planted to citrus.
Two of the trials were conducted in young replanted
citrus groves and one in an unplanted area of an older
bearing grove in order to avoid direct competition
from citrus trees and to minimize the effect of routine
grove operations on the growth of the legume crops.
MATERIALS AND METHODS
Experiment I. Experiment I was initiated in March
1975 in a young replanted citrus grove near Lake
Alfred. The soil on the experimental site was Candler
fine sand, a hyperthermic, uncoated Typic Quartz-
ipsamments. The site had been in citrus for over 50
years. The original planting of tangerines on rough
lemon rootstock was removed in 1973 and the grove
replanted to grapefruit in 1974. The young grapefruit
trees, spaced 6.1 x 9.1 m, served as corner markers for
the individual legume plots.
Before seeding, a fertilizer mixture of muriate of
potash and agricultural grade gypsum was broadcast
over the experimental area to supply 140 kg K, 180 kg
Ca, and 143 kg S/ha. The soil contained an adequate
level of available P and had a pH of 7.1. No fertilizer
N was used in the area in either 1974 or 1975 except
for that spread by hand beneath the canopy of each
tree.
The plots were seeded on March 12 using a hand
held broadcast seeder. The eight test legumes included
hairy indigo, Aeschynomene, and alyceclover seeded at
22kg seed/ha; cowpea, pigeonpea, and two soybean
cultivars, Jupiter and Hardee, seeded at 67 kg seed/ha;
and Stylosanthes, seeded at only 8 kg seed/ha because
of a limited supply of seed. The field design was a
randomized complete block with eight treatments
(legumes) and five blocks.
Commercial cowpea inoculum was used on all seed
except soybean which was treated with two sources of
Rhizobium japonicum inoculum, one applied to the
seed beans, the other, on a peat carrier, to the soil. Im
mediately following completion of the seeding opera
tion the area was disked in two directions. Irrigation
from overhead sprinklers was used periodically as
needed during the following weeks.
On June 2, the same eight legumes were seeded in
five additional blocks adjacent to the original site, em-
81
ploying the same procedures and techniques described
above.
Experiment II. Four of the legumes included in Ex
periment I were tested in a second experiment on
Candler fine sand, in an unplanted low, cold area of a
bearing orange grove. The area was bypassed in all
normal grove operations except for periodic cultiva
tion to control weeds. It was equipped with overhead
irrigation facilities, however, and had been limed at
some previous time, judging from the soil pH of 6.5.
The test crops, pigeonpea, alyceclover, Aeschynomene,
and Hardee soybean, were inoculated and seeded on
March 18 using the procedures described for Experi
ment I. The individual plot size was 3 x 15 m and the
field design was a randomized complete block having
four treatments (legumes) and three blocks. Only one
seeding date was employed in this experiment.
Experiment III. Experiment III was set out in a
bedded grove near Indiantown in Martin County. The
two 4-row beds used in the experiment had been in
citrus since 1960; however, the grove was abandoned in
1973 for economic reasons. The original trees were re
moved in 1974 and the beds replanted to orange trees
in February 1975. The spacing of the newly-planted
trees determined the dimensions of the legume plots,
4.6 x 8.2 m.
The soil was an alkaline, sandy clay loam, probably
of the Chobee series, a member of the fine loamy,
mixed, hyperthermic family of Typic Argiaquolls. The
beds were fertilized several days before seeding with a
mixture of muriate of potash and ordinary super
phosphate at a rate of 53 kg P, 115 kg K, 110 kg Ca,
and 87 kg S/ha. No N was used on the beds except in
the fertilizer applied by hand to the young citrus trees.
The test crops, seeded March 24, 1975, included
Crotalaria, pigeonpea, hairy indigo, Aeschynomene,
cowpea, alyceclover, Jupiter and Hardee soybeans, and
Florunner peanut (Arachis hypogeae L. cv. Florunner).
Crotalaria was seeded at 22 kg/ha, peanuts at 84 kg/ha.
The seeding rates for the others and the inoculation
and seeding procedures were identical to those used in
Experiment I. The field design was a randomized com
plete block with nine treatments and five blocks. The
plots were irrigated as needed with overhead sprinklers.
On June 5, five additional randomized complete
blocks were set out on an adjacent bed, testing the
same nine legumes.
The same harvesting procedure was used for all
three experiments. Forage yields were determined from
samples clipped at ground level from a 2 or 4 m2 area
near the center of each plot. The samples were weighed
in the field and again after drying at 65 C in a forced-
air oven. Subsamples of the oven-dried forage were
then ground in a Wiley mill and analyzed for N and,
for Experiment III, for P, K, Ca, and Mg also. The
crops were not harvested according to any fixed sched
ule; instead, each legume was harvested when it
reached the pod-filling stage which seemed to coincide
with maximum forage production (3). For some crops
this was closely followed by the beginning of defolia
tion.
RESULTS AND DISCUSSION
Experiment I. Good stands and vigorous early
growth were observed for all legumes seeded in March,
especially the grain legumes. Nodulation appeared to


82
Soil and Crop Science Society of Florida
be developing on most roots examined. But within 6
or 8 weeks after emergence, growth virtually ceased for
most of the crops. Plants wilted severely on hot and
windy days despite frequent irrigations from the over
head prinklers. On May 9, Dr. A. C. Tarjan, Uni
versity of Florida Nematologist, identified large popu
lations of ring and sting nematodes (Criconemoides
sp. and Belonolaimus sp., respectively) on soil and root
sample 5 collected from several locations in the experi
mental area. Only four of the eight legumes seeded in
March were subsequently harvested. (In contrast, the
cooperating citrus grower was unaware of the presence
of nematodes in the grove and was, in fact, pleased
with the growth and vigor of the young citrus trees.)
Hairy indigo produced approximately 10 tons dry
matter/ha, containing about 1.6% N (Table 1).
Stylosanthes and Aeschynomene produced about 5 tons
dry matter/ha. The total N content of hairy indigo,
calculated on the basis of a solid, one-hectare stand, was
significantly larger than for Stylosanthes or Aeschy
nomene. The data for cowpeas may not be valid since
the plants were very obviously infested with nematodes.
No data were obtained for any of the legumes
seeded in June as all were destroyed several days after
emergence by lesser corn stalk borer, identified by Dr.
E. B. Whitty, University of Florida Agronomist.
TABLE 1.Forage yield and nitrogen content of legume cover-
crops IN A YOUNG REPLANTED CITRUS GROVE ON CANDLER FINE SAND
IN POLK COUNTY, FLORIDA.
Seeding date
and crop
Harvest
date
Dry matter
yield
(kg/ha)
Nitrogen content
of forage
(%
dry wt) (kg/ha)
March 12
Flairy indigo
September 22
10,460 a*
1.59 b
166 a
Stylosanthes
September 22
5,580 b
1.72 b
96 b
Aeschynomene
September 22
4,619 b
1.83 b
84 b
Cowpea
May 23
870 c
2.79 a
24 c
*Data are means of 5 replications. Within each column, means
not followed by the same letter differ significantly at P = 5%.
Experiment. II. Forage and N yields were deter
mined for three of the four test legumes. The fourth
crop, soybean, was destroyed by grasshoppers. The
differences in forage production and in N content be
tween the three crops were not significant (Table 2).
All three grew satisfactorily. The comparisons of in
terest are between the data of this experiment and
those of Experiment I. Aeschynomene grew equally
well on both sites; in fact, forage yields and N content
data from the two experiments are almost identical.
Pigeonpea and alyceclover, which were destroyed by
nematodes on the old grove site of Experiment I, pro
duced good stands on the previously unplanted soil of
Experiment II. The soil in both locations was Candler
fine sand.
Experiment III. Only six of the nine legumes
seeded in March were harvested. Both soybean cultivars
were consumed by grasshoppers. The soybean data
from the June seeding also reflected insect damage to
an unknown extent. No information was obtained for
alyceclover for either seeding date because of rapid,
unexpected defoliation that occurred shortly before
the plots were to be harvested. Some of the crops were
grazed heavily by rabbits and rats. The cowpea and
peanut crops seeded in March seemed to be favored to
TABLE 2.Forage yield and nitrogen content of legume crops
GROWN ON PREVIOUSLY UNPLANTED CANDLER FINE SAND IN POLK
COUNTY, FLORIDA.
Nitrogen content
Dry matter f forage
Seeding date
and crop
Harvest
date
yield
(kg/ha)
(%
dry wt)
(kg/ha)
March 18
Pigeonpea
August 22
7,730*
1.89
146 a
Alyceclover
August 22
5,690
1.50
85 b
Aeschynomene
September 25
4,680
1.80
84 b
#Data are means of 3 replications. Within each column, means
not followed by the same letter differ significantly at P = 5% ex
cept that absence of letters denotes non-significance.
TABLE 3.Forage yield and mineral composition of legume covercrops in a young bedded
CITRUS GROVE ON CHOBEE SANDY CLAY LOAM IN MARTIN COUNTY, FLORIDA.
Seeding date
and crop
Harvest
date
Dry matter
yield
(kg/ha)
N
Mineral composition of forage
P K Ca
(% dry wt)
Mg
Total N
in forage
(kg/ha)
March 24
Cro talara
September 19
10,420 a*
2.62 a
0.16 b
1.22 c
1.33 b
0.27 b
273 a
Pigeonpea
Hairy indigo
August 20
10,660 a
1.77 be
0.15 b
1.07 c
0.81 c
0.17 c
189 b
September 19
7,010 b
1.25 d
0.13 b
1.33 c
1.33 b
0.23 b
88 c
Aeschynomene
September 19
6,990 b
1.48 cd
0.15 b
1.38 c
1.30 b
0.23 b
103 c
Peanut
August 6
2,020 c
2.07 b
0.14 b
1.72 b
1.73 a
0.33 a
43 d
Cowpea
June 3
850 c
2.48 a
0.28 a
2.47 a
1.28 b
0.26 b
21 d
June 3
Crotalaria
October 14
7,810 b
3.01 a
0.21 cd
1.49 c
0.83 c
0.21 c
235 a
Pigeonpea
October 14
11,780 a
2.07 cd
0.23 c
1.26 c
0.81 c
0.16 d
244 a
Hairy indigo
October 14
5,940 c
1.73 e
0.18 d
1.43 c
1.26 b
0.21 c
103 b
Aeschynomene
October 14
4,640 cd
1.79 e
0.22 cd
1.31 c
1.20 b
0.21 c
83 be
Peanut
August 20
2,890 e
2.53 b
0.20 cd
2.06 b
1.71 a
0.34 a
73 be
Cowpea
August 6
4,050 de
2.27 c
0.29 b
3.40 a
1.23 b
0.28 b
92 be
Soybean, Jupiter
August 20
3,090 e
1.99 de
0.32 ab
2.26 b
1.21 b
0.30 b
61 c
Soybean, Hardee
August 20
3,070 e
1.92 de
0.35 a
2.13 b
1.43 b
0.29 b
59 c
Data are means of 5 replications. Within each column, for each seeding date, means not followed by the same letter differ significantly
at P = 5%.


83
Proceedings, Volume 39, 1980
the point that their forage and N data are of question
able value.
The highest yields of dry matter were produced by
Crotalaria and pigeonpea, followed by hairy indigo
and Aeschynomene (Table 3). Essentially, the same
relative crop performance occurred in the June seed
ing, except that the forage yield of pigeonpea was sig
nificantly higher than for Crotalaria. Crotalaria had
the highest N content of the four legumes on both seed
ing dates.
Crotalaria produced the highest N yields, in excess
of 200 kg N/ha as calculated on the basis of a solid
one-hectare stand of legume. The June seeding of
jjigeonpea also exceeded 200 kg N/ha. Hairy indigo
and Aeschynomene produced approximately 100 kg
N/ha. The quantity of N contained in the roots of the
test crops was not determined.
The mineral composition of the forage seemed to
be characteristic of the particular crop, e.g. cowpeas
had the highest K content and one of the highest N
contents of all the legumes tested on both seeding
dates. Peanuts contained the highest and pigeonpea
the lowest Ca and Mg concentrations of all test crops
on both seeding dates.
In conclusion, the number and severity of the prob
lems encountered in this study provided a harsh but
effective test of performance for the legumes. (It
should be noted that some of the problems could have
been avoided if appropriate control measures had been
applied in anticipation of their occurrence.) Several of
the legumes grew very well under the conditions of
these tests and they should be investigated further to
determine their performance and compatibility with
citrus in older groves that are receiving normal grove
practices. The relative availability to citrus of the N in
the legume foliage will have to be determined in later
studies, as will the need for inoculation of the seed
prior to seeding.
LITERATURE CITED
1. Anderson, C. A. and L. G. Albrigo. 1973. Comparisons of soil
test methods for predicting the status of leaf Mg and Ca of
orange trees on Dolomite treated soil. Soil and Crop Sci. of
Fla. Proc. 32:149-152.
2. and Fred W. Bistline. 1978. Rate of nitrogen fer
tilization and incidence of blight in three orange groves on
the Ridge. Proc. Fla. State Hort. Soc. 91:59-61.
3. Hanway, J. J. and H. E. Thompson. 1967. How a Soybean
Plant Develops. Iowa State Univ. Coop. Ext. Ser. Spec. Re
port 53.
4. Nutman, P. S. 1976. IBP field experiments on nitrogen fixa
tion by nodulated legumes. In Symbiotic Nitrogen Fixation
in Plants, P. S. Nutman (ed.). Cambridge University Press,
Cambridge.
5. Rhoads, Arthur. S. 1936. Blighta non-parasitic disease of
citrus trees. Fla. Agr. Expt. Sta. Bui. 296. 64 pp.
Vegetation in Areas Stripmined for Phosphate
Robert M. Craig and Donald C. Smith1
ABSTRACT
Forty-five plant species were identified from a study
of 20 areas stripmined for phosphate. Fourteen of these
plants have features that make them useful for vege
tating stripmined areas.
Plant succession was determined and a revegetating
program proposed utilizing the plants identified as
contributing to ground cover and erosion control.
Bahiagrass (Paspalum notatum Fluegge), common
bermudagrass (Cynodon daclylon L. Pers.), hairy
indigo (Indigofera hirsuta L.), jointvetch (Aeschy
nomene americana L.), and alyce clover (Alysicarpus
vaginalis (L.) D.C.) are suggested for the initial es
tablishment period. Live oak (Quercus virginiana
Mill), water oak (Quercus nigra L.), and wax myrtle
(Myrica cerfera L.) can generally be established after
the spoil is several years old.
Additional Index Words: Paspalum notatum
Fluegge, Cynodon dactylon L. Pers., Indigofera hirsuta
L., Alysicarpus vaginalis (L.) D.C., Aeschynomene
americana L., Plant succession.
VEGETATION IN AREAS
STRIPMINED FOR PHOSPHATE
By 1974 there were almost 250,000 acres of land in
rStale Resource Conservationist, U.S.D.A., Soil Conservation
Service, P.O. Box 1208, Gainesville, FL 32602: Plant Materials
Specialist, U.S.D.A., Soil Conservation Service, Gainesville, FL.
Florida that were disturbed by surface mining, and this
had increased to 332,000 acres by 1977 (6). During the
same period acres of mined land reclaimed also in
creased from 32,000 to 45,000 acres. Most of the land
was stripmined for phosphate in Polk, Hillsborough,
and Hamilton Counties. By 1977, 181,000 acres had
been mined for this purpose (6).
Reclamation of surface mines is of interest to en
vironmentalists, conservationists, developers, and ulti
mately, every citizen who enjoys the products that re
sult from mining activities. The state of Florida has a
program addressing the reclamation of surface mines
for long-term beneficial land use. The rules are con
tained in Chapter 211, Part II, Florida Statutes and is
administered by the Department of Natural Resources.
The minimum standards (5) for a reclamation and
restoration program include revegetation of over 80
percent of the reclaimed land. Establishment of this
vegetation is often very difficult due to undesirable soil
conditions. This problem is recognized by the U. S.
Department of Agriculture, Soil Conservation Service
(SCS). The SCSs Long Range Plant Materials Program
for Florida gives the highest priority to the solution of
this problem (1). One of the initial efforts has been to
make a field study of native and naturalized plants
that occur on stripmined land. The study was started
in 1976 and completed in 1978 at locations throughout
Florida. This paper concerns only that portion of the
state that pertains to areas stripmined for phosphate.
The results are applicable only to overburden and not
to sand tailings.


84
Soil and Crop Science Society of Florida
The results indicate that several plants have a po
tential for use in revegetation of reclaimed land.
MATERIALS AND METHODS
All of the major areas stripmined for phosphate in
Florida were visited, and 20 sites were selected for de
tailed study. These sites adequately represented the
type of extent of conditions found on phosphate-
mined overburden in the counties of Hamilton, Hills
borough, and Polk that were area mined, as explained
by Imhoff, Fritz, and LaFevers (4). Observations and
determinations were made visually and were estimated.
A general survey of wide magnitude was used to obtain
information rather than a smaller number of more
detailed studies.
Data obtained at each site were: kind of mining,
age and type of spoil, soil conditions, topographic
features, existing erosion, plants occurring, erosion
control effectiveness, plant vigor, and management
treatments. The procedure was similar to the ones used
by Bryes and Miller (3) and Craig (2). Unknown
plants were sent to the University of Florida Herbar
ium personnel for identification. The data were proc
essed, stored, retrieved, and analyzed to determine
plant succession and related factors important in re
vegetating land minded for phosphate.
RESULTS AND DISCUSSION
Forty-five plant species were identified on over
burden material. Information on the number of total
sites where the plants occurred and related information
are shown in Tables 1, 2, 3, 4, and 5. Table 1 contains
data on trees; Table 2 on shrubs; Table 3 on vines;
Table 4 on grasses; and Table 5 on herbaceous plants.
Soil conditions were similar at each geographic
location. Sites generally had a soil pH of 6.0 or higher
and textures ranged from sand to loamy sand. Four of
the 20 sites had a pH of less than 6.0 but this did not
significantly alter the plant community.
The spoil age category in Tables 1-5 gives the age
of spoil where the plant occurred. Ages of the spoil
studied were 2, 3, 5, 6, 8, 20, 30, 33, 50, and 80 years.
Ratings include a numerical factor from 1 to 10 for
both plant vigor and the plants erosion control effec-
TABLE 1.Frequency and rating of trees on areas stripmined
FOR PHOSPHATE.
Scientific Name
Numberf
Spoil
Age
(Yrs)
Plant
Vigori
Erosion
Controli
Pinus elliottii Engelm
1
50
7
5
Prunus americana
Marsh.
1
50
5
5
Prunus sertina Ehrh.
1
50
5
5
Qiiercus laurifolia
Michx.
1
80
5
4
Qiiercus nigra L.
3
50
4
5
Quercus virginiana
Mill.
7
30-50
4
4
Sabal palmetto
(Walt.) Lodd.
1
80
5
4
Salix nigra Marsh.
1
50
5
5
f Number of sites plant occurred.
Rating for plant vigor and erosion control with 1 for most
effective, and 10 for least effective.
TABLE 2.Frequency and rating of shrubs on areas stripmined
FOR PHOSPHATE.
Scientific Name
Numberf
Spoil
Age
(Yrs)
Plant
Vigori
Erosion
Controli
Baccharis halimifolia L.
7
2-50
4
4
Callicarpa americana L.
1
50
5
7
Lantana cantara L.
3
2-50
4
4
Myrica cerfera L.
6
33-50
4
4
Psidium guajava Raddi
2
50
5
5
Sereonoa repens
(Bartr.) Small
2
50
5
3
fNumber of sites plant occurred.
Rating for plant vigor and erosion control with 1 for most
effective, and 10 for least effective.
TABLE 3.Frequency and rating of vines and vine-like plants
ON AREAS STRIPMINED FOR PHOSPHATE.
Spoil
Scientific Name
Numberf
Age
(Yrs)
Plant
Vigori
Erosion
Controli
Ampelopsis arbrea
(L.) Koehne
1
50
5
5
Rubus cuneifoius
Pursh
1
50
5
5
Smilax spp. L.
2
50-80
5
4
Vitis rotunifolia
Michaux
2
33-50
5
4
fNumber of sites plant occurred.
Rating for plant vigor and erosion control with 1 for most
effective, and 10 for least effective.
tiveness. One is for the most effective rating and 10 for
the least effective. Several of the plants have character-
istics which afford protection against erosion and en
croach naturally on these disturbed areas.
TABLE 4.Frequency and rating for grasses on areas strip-
mined FO PHOSPHATE.
Scientific Name
Numberf
Spoil
Age
(Yrs)
Plant
Vigori
Erosion
Controli
Andropogon cabanisii
Hack.
1
50
3
5
Andropogon glomeratus
Chapm.
4
5-50
4
6
Andropogon capillites
Nash.
1
50
3
5
Andropogon virginicus
L.
1
50
5
5
Cynodon dactylon (L.)
Pers.
2
2-20
5
5
Digitaria sanguinalis
(L.) Scop.
1
2
5
5
Panicum virgatum L.
1
2
3
3
Paspalum urvillei
Steud.
1
2
5
5
Rhynchelytrum roseum
(Nees) Stapf and
Hubb
7
2-50
4
5
Sporobolus poiretii
(Roem.) and Schult.
Hitchc.)
2
20-50
5
5
fNumber of sites plant occurred.
Rating for plant vigor and erosion control with 1 for most
effective, and 10 for least effective.


85
Proceedings, Volume 39, 1980
TABLE 5.Frequency and rate for herbaceous plants on areas
STRIPMINED FOR PHOSPHATE.
Scientific Name
Numberf
Spoil
Age
(Yrs)
Plant
VigorJ
Erosion
Control^
Aeschynomene americana
L.
4
2-6
4
3
A lysicarpus vaginalis
(L.) D.C.
1
2
1
3
Ambrosia artemisiifolia
L.
2
3-50
5
5
Bidens bipinnata L.
3
50-80
5
4
Cassia fasciculata
Michx.
1
3
5
5
Cyperus esculentus L.
2
2-20
4
3
Dichondra caroliniensis
Michx.
1
20
5
3
Eupatorium capillifolium
(Lam.) Small
12
2-50
4
4
Eleterotheca subaxillaris
(Lam.) Britt. & Rusby
1
5
3
5
Indigofera hirsuta L.
8
2-50
4
4
Lespedeza striata
(Thunberg) H. &. A.
1
20
5
3
Lippia nodiftora Michx.
1
20
5
3
Phaseolus lathyroides L.
1
2
1
3
Phytolacca americana L.
1
2
5
5
Sesbania exaltata (Raf.)
Rydberg ex A. W. Hill
2
2-50
4
4
Solidago spp. L.
1
2
5
5
Urena lobata L.
6
5-80
4
4
fNumber of sites plant occurred.
Rating for plant vigor and erosion control with 1 for most
effective, and 10 for least effective.
Of eight tree species that were noted, live oak
(Quercus virginiana Mill), and water oak (Quercus
nigra L.) were the most important.
Of six shrubs that were noted, eastern baccharis
(Baccharis halimifolia L.), wax myrtle (Myrica cerfera
L.), and lantana (Lantana camara L.) were most pre
valent.
Of four vines, the two most commonly found were
greenbriar (Smilax spp. L) and Muscadine grape
(Vitis rotundifolia Michaux). These vines are effective
for erosion control.
The growth habit and ability to grow and survive
under a wide range of soil environments make grass
especially valuable in preventing erosion and for re
vegetation. Of the ten grasses in Table 4, the four most
commonly found were natalgrass (Rhynchelytrum
roseum Nees, Stapf and Hubb), bushybeard bluestem
(.Andropogon glomeratus Chaprn.), common bermuda-
grass (Cynodon dactylon L. Pers.), and smutgrass
(Sporobolus poiretii) (Roem. and Schult.) Hitchc. The
occurrence of common bermudagrass is especially sig
nificant, since seed can be purchased commercially.
Seventeen herbaceous plants occurred but most of
them are annuals and have upright growth habits that
limit their effectiveness for permanent erosion control
and revegetation. Seed of several of the herbaceous
plants are available commercially, and they are recom
mended for planting during the initial establishment
period. These plants are: hairy indigo (Indigofera
hirsuta L.), jointvetch (Aeschynomene americana L.),
and alyce clover (Alysicarpus vaginalis L., D.C.)
Fourteen plantings by individual landowners were
also studied. Bahiagrass (Paspalum notatum Fluegge)
and common bermudagrass were the most effective and
commonly used plant species.
Plant Succession
Plant succession is an important factor in determin
ing the type of plants, i.e. trees, shrubs, vines, grasses,
and herbaceous plants to be utilized for revegetation.
This study of stripmined land from 2 to 80 years old
afforded a unique opportunity to study plant succes
sion on phosphate soil. Only frequently occurring
plants are used to show the following plant succession
stages.
The first and most important plants to become es
tablished during the first 5 years are herbs and grasses.
The herbaceous plants are dog fennel (Eupatorium
capillifolium Lam. Small), hairy indigo, Caesar weed
(Urena lobata L.), and iointvetch. The grasses are
natalgrass, bushybeard broomsedge, and common
bermudagrass. The two shrubs, eastern baccharis and
lantana, became established within the first 5 years.
After the spoil is several decades old, the pioneer
plants are joined by significant amounts of other herbs
and grasses. Woody plants also become more common,
with eastern baccharis, live oak, lantana, wax myrtle,
and muscadine grape being the most dominant.
After 50 years live oak, water oak, eastern baccharis,
wax myrtle, lantana, guava (Psidium guajava Raddi),
saw palmetto (Serenoa repens Bartr. small), and vari
ous vines become the dominant plants.
Plant Recommendations
It is logical to assume that a revegetation program
utilizing the planting and management of plants
identified as significant in the plant succession se
quence and otherwise commonly grown would be suc
cessful. The recommendations are to initially seed
combinations of bahiagrass, common bermudagrass,
hairy indigo, jointvetch, and alyce clover. Woody
plants will gradually become established by natural
encroachment but significant amounts do not occur
until after the spoil is 30 years old- It may become
necessary to establish woody plants. The recommended
trees and shrubs are live oak, water oak, wax myrtle,
and lantana. Germination of woody plant seed is
usually poor and unpredictable, but small plants can
often be transplanted wth good results.
The SCS is considering the study of several plants
that rated high in plant vigor and erosion control effec
tiveness but were relatively insignificant in occurrence.
These are for possible revegetation of areas stripmined
for phosphate. The plants being studied are African
stargrass, Cynodon plectostachyus (K. Schum.) Pilg.;
bitter panicum, Panicum amarum Ell.; bufflegrass,
Cenchrus ciliaris L.; herbaceous mimosa, Mimosa
strigillosa Torr. and Gray; lovegrass, Eragrostis spp.
Beauv.; maidencane, Panicum hemitomon Schult;
natalgrass, Rhynchelytrum roseum (Nees) Stapf and
Hubb.; sericea lespedeza, Lespedeza cuneata (Dumont)
G. Don; shoredune panicum, Panicum amarulum
Hitchc. and Chase; switchgrass, Panicum virgatum L.;
and virgata lespedeza, Lespedeza virgata A.P.D.C.
REFERENCES
1. Austin, W. E. 1974. Long range plant materials program
Florida. U.S.D.A., Soil Conservation Service, Gainesville. Flor
ida. Pp. 27.
2. Craig, R. M. 1974. Coastal dune vegetation. Proe. Fla, St,
Hor. Soc. 87:548-552.


Soil and Crop Science Society of Florida
86
3. Hutnik, R. J. and Grant Davis. 1969. Ecology and reclamation
of devastated land. Int. Sym. on Ecol. and Revegetation of
Drastically Disturbed Areas. Pennsylvania State Univ. School
of Forest Resources. Pp. 285-305.
4. ImHoff, E. A., T. O. Fritz, and J. R. LaFevers. 1976. A guide
to state programs for the reclamation of surface mined areas.
Geological Survey Circular 731, U. S. Department of the
Interior.
5. State of Florida. 1975. General rules governing the reclama
tion of sites of severance of solid minerals. Chap. 211, Part II,
Florida Statutes.
6. U.S.D.A., Soil Conservation Service. Estimate of status of
land disturbed by surface mining. (Unpublished).
Winter Hardiness in Limpograss, Hemarthria altissima1
A. J. Oakes2
ABSTRACT
Winter hardiness of limpograss, Hemarthria
altissima (Poir.) Stapf & C. E. Hubb., was determined
in field plantings at 24 locations in five plant hardiness
zones. Most locations are in the southeastern United
States, where the glass is most likely to be used in
agriculture. Significant differences in winter survival
were found among the 53 clones studied. These results
suggest considerable genetic variability within H.
altissima, so that winter-hardy germplasm might be
used to expand the production range and extend the
effective grazing period.
Additional Index Words: Cold-tolerant germplasm,
Plant introductions, Plant survival.
Hemarthria altissima (Poir.) Stapf & C. E. Hubb.,
commonly called limpograss (13), has become eco
nomically important as a pasture grass in the United
States during the past decade. A brief resume of its
introduction into American grassland agriculture has
been reported (6). Current production in Florida oc
cupies more than 6,000 ha and is worth more than
$1,000,000 (D. W. Jones, personal communication).
The known production range of limpograss in the
continental United States includes scattered plantings
throughout Florida, localized areas in states fringing
the Gulf of Mexico, and the Imperial Valley in Cali
fornia. After the introduction of four accessions in
1964 (6), vegetative propagating stocks were distrib
uted to Hawaii, Mexico, Central America, northern
South America (including Brazil), and the West
Indies. Additional collections were made in 1971 (6)
and 1976.
The objectives of this study were to evaluate H.
altissima germplasm for winter hardiness in field
plantings and to further delineate its potential pro
duction range.
Winter survival of forage crops under field condi
tions is affected by the latitude, elevation, exposure,
and slope of the planting site; the type, fertility, and
temperature and moisture-retention capacity of the
soil; and the extent to which herbage is removed (2-5,
11, 12). Consideration of all these factors and their
complex interactions is beyond the scope of this study.
The latitude and elevation and the minimum tempera
tures during the winter months are, however, con
iContribution of the Science and Education Administration,
USDA.
2Research Agronomist, SEA, USDA, Beltsville, MD 20705.
sidered; the last has previously been used as a criterion
for evaluation of winter hardiness in another warm-
season pasture grass, Digitaria (8, 9).
MATERIALS AND METHODS
All but one of the 53 limpograss clones tested
originated in South Africa; the exception, P.I. 367897,
came from Reunion Island. The ploidy levels in the
genome composition of clones in the collection dem
onstrate its genetic diversity (13). One clone, P.I.
364344 (2n=18), was collected in Lesotho at about
1,600 m elevation, but most other clones came from
elevations below 300 m at latitudes of 22-30 S. The
vegetative propagation stocks used in these trials were
supplied originally by the Germplasm Resources Lab
oratory, USDA, SEA, Beltsville, MD.
Plantings were made at 24 locations in 13 states,
including five plant hardiness zones (1). The avail
ability of propagating stocks determined the number
of clones evaluated and the evaluation period at any
given location; this resulted in different numbers of
clones being evaluated for different periods at the
various locations. Planting sites were selected so that
they would provide information about the effect of
climate on winter survival. The tests were conducted
on a wide variety of soils at different elevations with
various degrees of exposure. Major plantings were
made at eight locations in four plant hardiness zones
in six states in 1973, 1974, and 1975 (Table 1). Other
plantings, containing fewer entries, were made in dif
ferent years in Alabama, Arizona, California, Louisi
ana, North Carolina, Texas, and Virginia.
At the 24 locations, latitude ranged from 28 to 46
N; elevation, from 8 to 785 m; and minimum tempera
ture, from 1 to 18 C, in Ft. Pierce, FL, and Pullman,
WA, respectively, in each case. The minimum tem
peratures at the eight major locations during 1973-76
ranged from 4 to 18 C (Table 1).
All plantings were made early in the growing season
so that the plants would be well established before the
onset of the first winter. Cultivation and fertilization
were in accordance with local practices. State experi
ment stations, USDA Soil Conservation Service Plant
Materials Centers, and one USDA Plant Introduction
Station were the chief cooperators.
Winter survival was observed and recorded in late
spring each year. Grasses in the major plantings were
scored visually for survival of crowns within a plot by
use of the scale: 0 = no survival, 1 = 1-20% survival,
3 = 21-40% survival, 5 = 41-60% survival, 7 =
61-80% survival, and 9 = 81-100% survival. Survival


87
Proceedings, Volume 39, 1980
TABLE ].Latitude, minimum temperature, and number of limpocrass clones planted at eight
LOCATIONS IN FOUR PLANT HARDINESS ZONES.
Location
Latitude (N)
Min. temp (C)
No of clones planted
1973-74
1974-75
1975-76
1973
1974
1975
Brooksville, FL
28 33'
- 6
- 4
- 4
37
Gainesville, FL
29 40'
- 6
- 4
- 5
53
Americus, GA
32 04'
-11
- 6
- 9
37
45
37
Experiment, GA
33 10'
- 8
- 7
-13
42
Coffeeville, MS
33 59'
-11
-10
-13
19
Clemson, SC
34 41'
-11
- 8
-13
42
Beltsville, MD
39 02'
-15
-12
-15
38
52
Pullman, WA
46 46'
-18
-11
- 9
43
50
ratings were analyzed statistically by use of Duncans
Multiple Range Test when possible. Some cooperators
reported only survival vs. failure.
RESULTS AND DISCUSSION
The percent survival of each individual clone (Fig.
1) is calculated from the number of times it survived
divided by the total number of plantings in which it
was included (location-winters). For example, P.I.
299039 was included in plantings at eight locations; it
was evaluated for 1 year at four locations, 2 years at
three other locations, and 4 years at still another loca
tion, for a total of 14 location-winters. The lowest tem
perature survived by all 53 clones for at least one
location-winter was 9 C; 22 clones, or about 40% of
the collection, survived 15 C; and 5 clones survived
18 C (Fig. 1). Differential winter hardiness in H.
altissima is also apparent when the clones are grouped
according to overall percentage of survival, which
ranged from 38 to 69% for 13 clones, 70 to 79% for 25
clones, and 80 to 90% for 15 clones (Fig. 1). Although
more than 75% of the clones tested survived at least
70% of the location-winters, the data (Fig. 1) sub
stantiate the hypothesis that clones differ in ability to
survive low temperatures.
The clones introduced from South Africa in 1964,
P.I.'s 299993, 299994, and 299995, have been evaluated
more intensively than the other, newer introductions.
The clone P.I. 299039 from Rhodesia, however, has
received only limited attention because of its low pro
duction potential and its susceptibility to aphid dam
age (7). In the present study this clone survived three
winters at Pullman, WA, at temperatures near 15 C,
Fig. 1.'Winter survival of 53 limpograss clones grown for
variable periods at 24 locations in five plant hardiness zones.
but died at Beltsville, MD, at similar temperatures. Its
vigor was also low in Florida (S. C. Schank, personal
communication). The other three clones are now in
commercial production under the cultivar names
Redalta P.I. 299993, Greenalta P.I. 299994, and
Bigalta P.I. 299995 (10). Their overall percentages of
survival were 84%, 78%, and 76%, respectively (Fig.
1). New plantings of all three clones survived at 15 C
at Beltsville, but the year-old stands died at 12 C the
next winter. These clones have survived 6 C at two
Florida locations, Brooksville and Gainesville (Table
1). New plantings of the diploid cultivars, Redalta
and Greenalta (13), survived 7 C at Experiment,
GA, and survived 13 C the next winter; the tetraploid
cultivar, Bigalta, did not survive even the first winter.
Of the newer introductions, P.I.s 349797, 349798,
364344, and 364891 were the most cold tolerant clones
at Beltsville, MD. The clone P.I. 349798 also survived
13C at Clemson, SC, and its overall percentage of
survival was 90% in 10 location-winters (Fig. 1).
Newly established plantings of P.I. 364891 survived
two winters at Beltsville, MD, at minimum tempera
tures of 12 and 15 C, and five winters at Pullman,
WA, during two of which the minimum temperature
was 18 C. Four other clones, P.I.s 364861, 364865,
364876, and 364886, also survived at 18 C at Pull
man, WA (Fig. 1). Of all clones tested, P.I. 364344,
from the high elevation in Lesotho, was most cold
tolerant; its overall percentage of survival was 90% in
31 location-winters, which included 18 locations.
Differences in survival ratings were not statistically
significant (P = 0.05) among 17 of 20 clones, all grown
in each of three locations (Americus and Experiment,
GA, and Clemson, SC) in 1975-76. However, the sur
vival ratings of P.I.s 349749 and 364863 were signif
icantly (P = 0.05) higher than that for P.I. 364867; in
addition, P.I. 364863 was superior to that of seven
clones. The minimum temperatures and mean per
centages of survival at Americus, Experiment, and
Clemson for the winter of 1975-76 were 9 C and
75%, 13 C and 85%, and 13 C and 85%, respec
tively. The mean survival rating at Clemson, 4.5, was
significantly higher (P = 0.05) than those of Americus
and Experiment (3.0 and 3.3, respectively). Differences
in mean survival ratings at the three locations are not
obviously related to either minimum temperature or
the number of days below freezing during the winter.
The rating differences may be attributable to sub
jective differences in the use of the scale by evaluators.
Ratings of the 20 clones tested at these three locations
suggest that survival of P.I. 364863 is superior to that
of the remaining 19 clones.


88
Soil and Crop Science Society of Florida
Survival ratings were compared for 29 clones, all
grown at both Americus and Experiment, GA. These
clones were rated for the winters of 1973-74, 1974-75,
and 1975-76 at Americus, and for the latter two winters
at Experiment. At Americus, mean survival ratings
were significantly (P = 0.05) higher for the first two
winters than for the third winter. The minimum tem
peratures for the three winters were 11, 6, and
9 C, respectively (Table 1). Survival ratings ranged
from 2.7 to 8.0; that for P.I. 367897 was significantly
(P = 0.05) higher than those for P.I. 347238 and P.I.
364872, but there were no other significant differences
among ratings. The low-temperature stress apparently
was not sufficient to reveal many differences in winter
hardiness.
These 29 clones behaved similarly during the
winters of 1974-75 and 1975-76 at Experiment, GA.
The mean survival rating for the first winter, 4.9, was
significantly (P = 0.05) higher than that for the second
winter, 3.5, with minimum temperatures of 7 and
13 C, respectively. Survival ratings ranged from 0 to
7; one clone was lost the first winter and four were lost
the next winter. The survival ratings of P.I.s 364863,
364888, 364889, and 364890 were significantly (P = 0.05)
higher than those of seven other clones: P.I.s 349750,
349753, 364862, 364867, 364868, 378086, and 379617.
Like the mean survival ratings for each location,
mean ratings for both Americus and Experiment com
bined were significantly (P = 0.05) higher for the winter
of 1974-75 (5.4) than for the winter of 1975-76 (3.5).
The difference in the mean survival ratings for the two
locations for the winter of 1975-76 was not significant
(P = 0.05). Five clones failed at Americus and four at
Experiment during that winter; two of these failed at
both locations. The behavior of all clones was generally
similar at these two locations.
These results are indicative of the genetic variabil
ity within H. altissima. The winter-hardy germplasm
identified in this study may be used to expand the pro
duction range and extend the effective grazing period
of limpograss in the contiguous United States. The
production range of limpograss may be extended to
higher elevations in the Tropics and subtropics
through the use of this colcl-tolerant germplasm. This
winter-hardy germplasm may be used in plant improve
ment programs or in its unaltered form.
ACKNOWLEDGMENTS
The author expresses his appreciation to those who
assisted in these trials. Special thanks are given to B. B.
Billingsley, John Powell, and R. D. Roush, who col
lected winter-hardiness data in Mississippi, Georgia,
and Florida, respectively; to A. M. Davis, G. W. Evers,
A. E. Kretschmer, Jr., W. R. Langford, E. F. McClain,
and S. C. Schank for their contributions; and to
E. James Koch for assistance in the statistical treatment
of the data.
REFERENCES
1. Anonymous. 1972. Plant hardiness zone map. USDA-ARS
Mise. Pub. 814.
2. Dunavin, L. S., Jr., and O. C. Ruelke. 1959. The evaluation
of cold hardiness in Florida pasture grasses. Soil and Crop
Sci. Soc. Florida, Proc. 19:172-178.
3. McCloud, D. E., and John Creel, Jr. 1957. Nitrogen in rela
tion to winter-kill: Bermuda vs. Pangla. Plant Food Rev.
3(1):18-19.
4. C. S. Hoveland, O. C. Ruelke, L. S. Dunavin, Jr.,
and H. C. Harris. 1957. Physiological responses of Florida
forage crops to environmental variables. Florida Agrie. Exp.
Stn. Ann. Rep., pp. 46-47.
5. V. N. Schroder, K. D. Butson, and O. C. Ruelke.
1957. Measurement of meterological elements of the micro
climate. Florida Agrie. Exp. Stn. Ann. Rep., pp. 49-50.
6. Oakes, A. J. 1973. Hemarthria collection from South Africa.
Turrialba 23:37-40.
7. 1978. Resistance in Hemarthria species to the
yellow sugarcane aphid, Sipha flava (Forbes). Tropical Agrie.
(Trinidad) 55(4):377-381.
8. W. R. Langford. 1967. Cold tolerance in
Digitaria. Agron. J. 59:387-388.
9. W. R. Langford, and S. C. Schank. 1970. Winter
hardiness in Digitaria. Soil and Crop Sci. Soc. Florida, Proc.
30:222-229.
10. Quesenberry, K. H., et al. 1978. Redalta, Greenalta and
Bigalta limpograss, Hemarthria altissima, Promising forages
for Florida. Univ. Florida IFAS Bull. 802, 18 pp.
11. Ruelke, O. 1963. Winter injury to Floridas pastures. Soil and
Crop Sci. Soc. Florida, Proc. 23:194-198.
12. 1966. Potassium fertilization influence on winter
survival of pangolagrass. Soil and Crop Sci. Soc. Florida, Proc.
26:231-238.
13. Wilms, H. J., J. W. Carmichael, and S. C. Schank. 1970.
Cytological and morphological investigations on the grass
Hemarthria altissima (Poir.) Stapf et C. E. Hubb. Crop Sci.
10:309-312.
Ij ; .i
Reaction of Stylosanthes hamata (L.) Taub. Indigenous to
Southeast Florida to Colletotrichum gloeosporioides (Penz.) Sacc.
R. M. SONODA AND J. B. BROLMANN
ABSTRACT
Colletotrichum gloeosporioides (Penz.) Sacc. was
the only species of Colletotrichum isolated from dark
lesions on leaves of native Stylosanthes hamata (L.)
JJiub. grown at the Agricultural Research Center, Fort
-"CTT ;
rFlorida Agricultural Experiment Station Journal Series No.
2116.
-Associate Professor (Associate Plant Pathologist) and Assistant
Professor (Assistant Legume Breeder), respectively, Agricultural
Research Center, Fort Pierce, Florida, 33450.
Pierce (ARC-FP) in the summer of 1979. In a survey
made in the summer of 1979, C. gloeosporioides was
not found in native stands of S. hamata along the
southeast coast of Florida. S. hamata clones collected
from 36 locations throughout the southeast coastal
areas of Florida were inoculated with a spore suspen
sion made with eight isolates of C. gloeosporioides ob
tained from lesions on S. hamata at the ARC-FP. About
58% of the collection was not infected and 33% was
lightly infected. Three clones had a moderate level of
leaf and stem lesions. Most native Florida S. hamata


89
Proceedings, Volume 39, 1980
genotypes appear to be resistant to or only lightly
affected by the strain or strains of C. gloeosporioides
present in southeast Florida.
Additional Index Words: Anthracnose.
Stylosanthes hamata (L.) Taub. accessions have
shown promise as forage in the tropics and subtropics,
including south Florida (1). Several endemic S. hamata
ecotypes collected from stands in southeast Florida are
being tested for forage use in south Florida (1).
Anthracnose incited by Colletolrichum gloeosporioides
(Penz.) Sacc. is a limiting factor in the use of
Stylosanthes spp. for forage in various parts of the
tropics and subtropics (J. M. Lenne, Centro Inter
nacional de Agricultura Tropical, personal communi
cation). C. gloeosporioides was found affecting
Stylosanthes spp., including S. hamata, in Florida in
1971 (11). Several S. hamata accessions native to south
east Florida were naturally infected with Colletotri-
chum spp. when planted in pots at the Agricultural
Research Center, Fort Pierce (ARC-FP) in 1974 (10).
No Colletolrichum lesions were found on S. hamata in
a limited survey of native stands of the plant in Palm
Beach and Dade counties in 1973 (8). A second
Colletolrichum spp., S. demaiium f. sp. trncala
(Schw.) v. Arx, was isolated from Stylosanthes spp. in
1978 and was pathogenic to S. hamata in pathogenicity
tests (5).
The objectives of the present work were to: deter
mine relative incidence of C. gloeosporioides and C.
dematium f. sp. trncala in S. hamata plantings at
the ARC-FP, survey native stands of S. hamata
along the southeast coast of Florida for presence of
Colletolrichum spp., and to determine relative suscep
tibility of collections of S. hamata native to southeast
Florida to C. gloeosporioides.
MATERIALS AND METHODS
Native stands of S. hamata were surveyed in July,
1979 for presence of Colletotrichum lesions. Observa
tions were made at approximately 45 different loca
tions where S. hamata was found, from Stuart south to
Miami.
Leaves with dark lesions were collected from a
planting at the ARC-FP of two Florida accessions of
S. hamata. Small pieces of diseased tissue (approxi
mately 25 mm2) were surface sterilized in 0.525%
NaOCl, blotted on paper towels, and plated on oat
meal agar (OMA) (4). The plates were incubated on
the laboratory bench (25 to 29 C) for 5 to 10 days.
Identification of the fungi developing on OMA was
made directly on the plates or by transferring mycelia
and spores to microscope slides. Eight isolates identified
as C. gloeosporioides were transferred to fresh OMA
and maintained by serial transfers on OMA.
Inoculum of C. gloeosporioides was increased by
spreading spores from a 4-day-old culture grown on
OMA on a fresh OMA plate with a sterilized 5-mm
diameter glass rod with a rounded end and incubating
the cultures at room temperature (25 to 29 C) for 5
days. Spores formed on these plates were suspended in
sterile distilled water. Spore suspensions from eight
isolates were combined and spore concentration ad
justed to 9 x 105 spores per ml.
Stem cuttings (8 to 10 cm) were made for single
plants in 36 stands of .S, hamata from Flobe Sound to
Miami and from seven plants each within one city
block areas in Deerfield Beach and Miami. Stem cut
tings were also made from accession 7303, an accession
obtained from Riviera Beach, FL in 1971, showing
promise for forage but whose yield at the ARC-FP was
reduced by C. gloeosporioides (6). The cuttings were
placed in dune sand from Ft. Pierce or in virgin
Oldsmar fine sand in plastic trays in the greenhouse.
In 4 weeks, rooted cuttings were transplanted to a 50%
mixture of virgin Oldsmar fs and dune sand in 180 ml
styrofoam cups. After transplanting, the plants were
grown for 4 more weeks before inoculation with C.
gloeosporioides.
The cups with S. hamata cuttings were placed
randomly in plastic bags. There were four replicates
of two plants of each accession. The plants were
sprayed with the suspension of C. gloeosporioides with
an atomizer. The bags were closed after inoculation
and plants incubated at room temperature (26 to 29 C)
for 40 hrs. The cups were removed from the bags and
placed on a greenhouse bench in a randomized com
plete block arrangement. Eight days after inoculation,
disease incidence was recorded and a disease severity
index (DSI) calculated (11). The rating system used
was 1 = no lesions, 2 = 1 to 3 lesions per plant, 3 = 4
to 8 lesions per plant, 4 = scattered lesions, 5 = some
defoliation, and 6 = plants dead. There were between
five and eight true leaves per cutting.
RESULTS
No Colletotrichum spp. lesions were found on S.
hamata in any of the stands surveyed along the south
east coast of Florida. A light incidence of lesions in
cited by Curvularia spp. was found in some of the
stands.
C. gloeosporioides was consistently isolated from
dark lesions on S. hamata at the ARC-FP. No. C.
dematium f. sp. truncata was isolated.
Most of the 36 accessions of S. hamata collected
from throughout southeast Florida were not infected
(58%) (Fig. 1) or only lightly affected (DSI of 1.1 to
2.0) (33%). Only three accessions were moderately
affected (DSI 2.1 to 3.0). The high F value for treat
ment, 23.99, on analysis of variance indicated that
there were significant differences in susceptibility be
tween the different accessions.
There was no statistical difference in susceptibility
between plants within a city block. Plants from ac
cession 7303 were severely affected with a DSI of 3.5.
DISCUSSION
The absence of C. gloeosporioides from native
stands of S. hamata in southeast Florida and its pres
ence in experimental plantings of plants arising from
seed imported from other areas of the tropics and sub
tropics where the pathogen was reported earlier (11)
indicate that the pathogen was introduced to Florida.
The fungus is seed-borne and was probably introduced
on seed contaminated with the fungus. The disease
was found in Ft. Pierce in 1971. The reason that the
fungus has not spread to native S. hamata stands is
unknown.
The most susceptible Florida S. hamata so far


90
Soil and Crop Science Society of Florida
22 -
1.0 1.1-1.5 1.6-2.0 2.1-2.5 2.6-3.0
DISEASE SEVERITY INDEX
Fig. 1.Distribution of disease severity ratings for Stylosanthes
hamata ecotypes native to south Florida inoculated with Col
letotrichum gloeosporioides.
found, accession 7303, is not killed by the fungus.
Foliage production and possibly stem growth is low
ered, however. Accession 7303 and other susceptible
native S. hamata may be less able to compete under
natural conditions if C. gloeosporioides was intro
duced into the native stands. If the pathogen is intro
duced to native S. hamata stands, the relatively high
tolerance of most native 5. hamata to the C. gloeo
sporioides strain or strains present in Florida, however,
will probably prevent this disease from having much
impact on the total S. hamata stand. There are other
strains of C. gloeosporioides pathogenic to Stylosanthes
spp. in other parts of the world (3, 9), however. Some
of these may cause more severe damage to S. hamata
indigenous to south Florida if introduced. Efforts
should be made to keep other strains of C. gloeo
sporioides from entering Florida. Treatment with
sulfuric acid has been found to reduce or eliminate
inoculum of the pathogen from seeds (2).
C. gloeosporioides appears to be the more im
portant of the two Colletotrichum spp. reported on S.
hamata. C. dematium f. sp. truncata was isolated only
once from S. hamata at the ARC-FP in 1977 (7).
Further isolations at different times of the year will be
needed to determine if the ratio of C. gloeosporioides
to C. dematium f. sp. truncata infections are deter
mined by seasonal differences.
Other native Florida S. hamata ecotypes apparently
more resistant to the strains of C. gloeosporioides pres
ent in Florida will have to be tested for forage po
tential as possible replacement for accession 7303,
which has good agronomic characteristics but whose
yield is greatly affected by the disease. It may also be
possible to develop resistant S. hamata lines with
agronomic characters similar to accession 7303 by
breeding. No work, however, has yet been done to
determine the mechanism of inheritence of resistance
of Stylosanthes spp. to C. gloeosporioides.
LITERATURE CITED
1. Brolmann, J. B. 1979. Distribution and significance of
Stylosanthes hamata (L.) Taub. in south Florida. Florida
Scientist 42:63-64.
2. Ellis, M. A., J. E. Ferguson, B. Grof, and J. B. Sinclair. 1976.
Transmission of Colletotrichum gloeosporioides and effect of
sulfuric acid scarification on internally seed-borne fungi in
seeds of Stylosanthes spp. Plant Dis. Reptr. 60:844-846.
3. Irwin, J. A. G., and D. F. Cameron. 1978. Two diseases of
Stylosanthes spp. caused by Colletotrichum gloeosporioides
in Australia, and pathogenic specialization within one of the
casual organisms. Aust. J. Agrie. Res. 29:305-317.
4. Lenne, J. M., and R. M. Sonoda. 1977. Rhizopus stolonifer
(Ehr. ex Fr.) Lind., a seed-borne fungus of Stylosanthes
hamata (L.) Taub. in Florida. Soil Crop Sci. Soc. Fla. Proc.
37:39-42.
5. Lenne, J. ¡VI., and R. M. Sonoda. 1978. Occurrence of
Colletotrichum dematium f. sp. truncata on Stylosanthes
spp. Plant Dis. Reptr. 62:641-644.
6. Lenne, J. M., and R. M. Sonoda. 1979. Effect of anthracnose
caused by Colletotrichum gloeosporioides on yield of Stylo
santhes hamata. IX International Cong. Plant Protection.
Wash. D. C. Abstract 858.
7. Lenne, J. M., and R. M. Sonoda. 1979. The occurrence of
Colletotrichum spp. on Stylosanthes spp. in Florida and the
pathogenicity of Florida and Australian isolates to Stylo
santhes spp. Trop. Grassl. 13:98-105.
8. Sonoda, R. M. 1973. Incidence of Colletotrichum leaf spot
and stem canker on introductions and selections of Stylo
santhes humilis. Plant Dis. Reptr. 57:747-749.
9. Sonoda, R. M. 1974. Disease of Stylosanthes spp. Ft. Pierce
ARC Research Report RL-1974-4.
10. Sonoda, R. M. 1974. Identifying and evaluating diseases of
tropical and subtropical forage crops. Soil Crop Sci. Soc. Fla.
Proc. 34:156-158.
11. Sonoda, R. M A. E. Kretschmer, Jr., and J. B. Brolmann.
1974. Colletotrichum leaf spot and stem canker on Stylo
santhes spp. in Florida. Trop. Agrie. (Trinidad) 51:75-79.
Effect of Nematicides and Application Methods on
Sting Nematode Control, Root Nodulation,
and Yield of Soybeans1
H. L. Rhoades2
ABSTRACT
In-row applications of the soil fumigants, DBCP
and EDB, at 13.4 and 35.8 kg/ha, respectively, and the
iFlorida Agricultural Experiment Station Journal Series No.
2137.
2Nematologist, AREC-Sanford, P. O. Box 909, Sanford, FL
32771.
nonvolatile nematicides, phenamiphos, carbofuran,
aldicarb, oxamyl, and ethoprop at 2.2 kg/ha effec
tively reduced populations of the sting nematode,
Belonolaimus longicaudatus, Rau, 1958, and signif
icantly increased yields of soybean (Glycine max (L.)
Merr.). Both control of B. longicaudatus and yield
increases were similar when granular formulations of
phenamiphos, carbofuran, aldicarb, and oxamyl were


Proceedings, Volume 39, 1980
applied as 38-cm bands incorporated 5-8 cm deep just
prior to planting, as 25-cm bands pressed into the soil
surface by the press wheel of the planter, and in the
seed furrow. None of the nematicides, or methods of
application adversely affected root nodulation from
Rhizobium japonicum. Severe phytotoxicity and yield
reduction occurred in ethoprop treated plots following
application of the herbicide, metribuzin. This ap
peared to be caused by an interaction between these
materials.
Additional Index Words: Belonolaimus longi-
caudatus, Glycine max, Rhizobium japonicum, Metri
buzin, Soil fumigants, Nonvolatile nematicides.
Numerous nematodes cause serious injury to soy
beans (Glycine max (L.) Merr.). One of the most
destructive is the sting nematode, Belonolaimus longi-
caudatus, Rau, 1958, when the crop is produced on the
fine sandy type soils of Florida. Soybean is an excellent
host of this nematode (8) and populations increase
rapidly during the growing season, often resulting in
heavy yield losses. Several workers (2, 4, 5, 7) have re
ported increased yields of soybeans in recent years
through control of various nematodes with nemati
cides, and Sasser et al. (7) found that the sting nema
tode was effectively reduced and yields increased sig
nificantly by the soil fumigant, DBCP, and the non
volatile nematicides, carbofuran and ethoprop.
in addition to the efficacy of the various nematicides
for controlling nematodes, additional information is
needed on their effects on root nodulation from
Rhizobium japonicum under Florida conditions.
Reddy and Kumar Rao (6) reported no deleterious
effect on nodulation from recommended doses of
fensulfothion, oxamyl, methomyl, carbofuran, and
aldicarb in India.
The primary purpose of the experiments reported
here was to study the effects of selected volatile and
nonvolatile nematicides and application methods on
control of the sting nematode, root nodulation, and
yield of soybeans under field conditions in Florida.
MATERIALS AND METHODS
Single experiments were conducted in 1977 and
1978 on Myakka fine sand at the Agricultural Research
and Education Center, Sanford, Florida. Populations
of sting nematodes had developed to injurious levels
on winter cover crops of rye grown prior to the experi
ments. Other plant parasitic nematodes present but in
numbers too low to significantly affect yields were
Paratrichodorus christiei (Allen, 1957) Siddiqi, 1973,
and Hoplolaimus galeatus (Cobb, 1913) Sher, 1961.
The experiments were of randomized complete block
design with five replicates. Plots were 1.52 m wide (2
rows) and 12.2 m long.
Nematicides included were:
(1) l,2-dibromo-3-chloropropane (DBCP)
(2) 1.2-dibromoethane (EDB)
(3) ethyl 4-(methylthio)-m-tolyl isopropylphosphorami-
date (phenamiphos)
(4) 2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcar-
bamate (carbofuran)
(5) 2-methyl-2-(methylthio)propionaldehyde 0-(methyl-
carbamoyl)oxime (aldicarb)
91
(6) methyl n, N-dimethyl-A7-[(methylcarbamoyl)oxyl]-
1-thiooxaminidate (oxamyl)
(7) O-ethyl S,S-dipropyl phosphorodithioate (ethoprop)
The soil fumigants, DBCP and EDB, were applied
in 1977 and 1978, respectively, for comparison with the
nonvolatile materials. Both were injected 15-18 cm
deep in-the-row with a single chisel at rates of 13.4
kg/ha of DBCP and 35.8 kg/ha of EDB the day before
planting. The nonvolatile materials were applied as
granular formulations in-the-row at 2.2 kg a.i./ha. All
were applied in 38-cm bands and incorporated 5-8 cm
deep with spiked rotary wheels just prior to planting
and as 25-cm bands between the planting shoe and
press wh ;cl during the planting operation. In addition,
all but (thoprop were applied in the seed furrow dur
ing the j lanting operation as a third method. Bragg,
a variet) of soybean resistant to the southern root-knot
nematochi (Meloidogyne incognita), was planted in
both experiments with a granular formulation of
Rhizobium japonicum drilled just below the seed
level. Cultural practices, in general, were consistent
with normal practices of the area. A herbicide was not
used in 1977 but metribuzin was applied on all plots
in 1978. Sixty days after seeding, six random plants
were dug from each plot and the nodules counted. Soil
samples consisting of five random cores from each plot
were collected approximately 8 weeks after planting
for nematode population determination by centrifugal-
flotation (3). Soybean yield data were obtained by
harvesting 4.57 m of row from the center of each plot.
RESULTS AND DISCUSSION
The data in Table 1 indicate that none of the
nematicides or the method of application adversely
affected root nodulation. Although the number of
nodules was highly variable on individual plants,
average numbers were not significantly different from
those from check plots.
All of the nematicides greatly reduced sting nema
tode populations; the soil fumigants and phenamiphos
provided the best control. Although there was con
siderable variation in population counts, the data indi
cated that application method made little difference in
the efficacy of the three methods of applying the gran
ular materials. Excellent growth and yield responses
were obtained from all nematicide treatments (Table
1). Yield increases were significantly higher for all
treatments over check plots except for ethoprop ap
plied in the 25-cm band in 1978. This reduction in
yield for ethoprop in 1978 as compared to 1977 ap
parently was caused by severe phytotoxicity from an
interaction of this material and the herbicide, metri
buzin. Symptoms, beginning approximately 2 weeks
after planting, consisted of chlorosis, leaf burn, stunt
ing, and some loss of stand. Although considerable
recovery occurred later, final yield was greatly reduced.
Some of these symptoms also occurred at the same time
in the treatments from phenamiphos; however, they
were much less severe and there appeared to be com
plete recovery with little or no loss in yield. This
phenomenon has occurred before when metribuzin was
applied following application of organophosphorus
nematicides (1) and similar combinations should be
avoided. No injury resulted from metribuzin in com
bination with the carbamate or carbamoyl materials,
carbofuran, aldicarb, and oxamyl.


92
Soil and Crop Science Society of Florida
TABLE 1.Effect of nematicides on sting nematode populations, root nodulation, and yield
OF SOYBEANS.
Treatment
Application
Rhizobium
nodulesf
Sting
Nematodes*
Yield
(kg/ha)
1977
1978
1977
1978
1977
1978
Check

86
48
96
75
1949
1613
DBCP, 13.4 kg/ha
Chisel
95

18

4301

EDB, 35.8 kg/ha
rr

59

2

3696
Phenamiphos, 2.2 kg/ha
38-cin band
69
62
2
4
3965
3763
//
rr
rr
25-cm "
105
71
1
2
3763
3427
//
rr
rr
seed furrow
96
82
7
17
4435
3696
Carbofuran,
tr
rr
38-cm band
86
45
36
27
4099
3494
//
//
rr
25-cm "
75
64
38
28
3898
3427
//
rr
rr
seed furrow
85
43
14
34
3898
2822
Aldicarb,
rr
n
38-cm band
68
54
19
7
3965
3293
//
rr
rr
25-cm "
95
64
25
11
4032
3427
//
rr
rr
seed furrow
88
52
32
20
3898
2957
Oxamyl,
rr
rr
38-cm band
53
50
49
44
3965
3226
It
rr
rr
25-cm "
95
58
63
19
3965
3427
II
rr
rr
seed furrow
63
52
63
21
3629
3091
Ethoprop,
rr
rr
38-cm band
69
33
36
24
4032
2554
//
rr
rr
25-cm "
62
43
29
46
3898
2083
LSD .05
N.S.
25
739
874
.01
34
1008
1156
fAverage number per plant.
JAverage number of sting nematodes extracted from 100 cc of soil.
Although most o£ the materials used in these tests
also possess insecticidal properties and may have in
creased growth and yield in part through control of
insects, it appears that most of the benefit came
through control of the sting nematode. Treated plots
not only had increased growth and yield, but had
plants with much larger root systems and greatly re
duced nematode injury symptoms.
LITERATURE CITED
1. Anon. 1979. Metribuzin herbicides vs. organophosphate nem
aticides. Florida Cooperative Extension Service. Entomology
and Nematology News 5(2) :3-4.
2. Blackmon, C. W., and H. L. Musen. 1974. Control of the
Columbia (lance) nematode Hoplolaimus columbus on Soy
beans. Plant Dis. Reptr. 58:641-645.
3. Jenkins, W. T. 1964. A rapid centrifugal-flotation technique
for separating nematodes from soil. Plant Dis. Reptr. 48:692.
4. Kinloch, R. A. 1974. Response of soybean cultivars to nema-
ticidal treatments of soil infested with Meloidogyne incog
nita. J. Nematol. 6:7-11.
5. Minton, N. A., M. B. Parker, O. L. Brooks, and C. E. Perry.
1979. Effects of nematicide placement on nematode popula
tions and soybean yields. J. Nematol. 11:150-155.
6. Reddy, D. D. R., and J. V. D. K. Kumar Rao. 1975. Effect of
selected nonvolatile nematicides and benomyl on nodulation,
root-knot nematode control, and yield of soybeans. Plant Dis.
Reptr. 59:592-595.
7. Sasser, J. N., K. R. Barker, and L. A. Nelson. 1975. Chemical
soil treatments for nematode control on peanut and soybean.
Plant Dis. Reptr. 59:154-158.
8. Tomerlin, A. H., Jr., and V. G. Perry. 1967. Pathogenicity of
Belonolaimus longicaudatus to three varieties of soybean
(Abstr.). Nematologica 13:154.
Forage Production From Pearl Millet Following Rye and
Ryegrass Fertilized With Sulfur-Coated Urea1
L. S. Dunavin2
ABSTRACT
The use of fertilizer materials with a slow release
rate has accentuated the need to determine the value
of residuals to succeeding crops. This investigation was
cpnducted over a period of two years to ascertain the
value of residuals by determining yield and nitrogen
(,N) uptake by pearl millet [Pennisetum americanum
iFlorida Agrie. Exp. Stn. Journal Series No. 400.
^Associate professor (associate agronomist), Agrie. Res. Center,
IFAS, Univ. of Florida, Jay, FL 32565.
(L.) K. Schum.] when it followed rye (Secle cereale L.)
and ryegrass (Lolium multiflorum Lam.) fertilized
with sulfur-coated urea (SCU) and ammonium nitrate
(AN). Compositions of SCU having dissolution rates of
10, 20, and 30% (dissolution in water in 7 days) were
each applied to the winter crops at annual rates of 100,
200, and 400 kg/ha of N. Ammonium nitrate was aj>
plied at the same rates of N in one or three applica
tions. Additional AN was applied to millet at 50, 100,
and 200 kg/ha of N on plots which had received 100
kg/ha of N from AN during the rye and ryegrass


Full Text
SOIL and CROP SCIENCE
SOCIETY of FLORIDA
PROCEEDINGS
VOLUME 39
1980
THIRTY-NINTH ANNUAL MEETING
BREVARD AGRICULTURAL CENTER
FRANK WOLFE'S BEACHSIDE MOTEL
COCOA BEACH, FLORIDA
OCTOBER 2-4, 1979


SOIL and CROP SCIENCE
SOCIETY of FLORIDA
PROCEEDINGS
VOLUME 39
1980
THIRTY-NINTH ANNUAL MEETING
BREVARD AGRICULTURAL CENTER
FRANK WOLFE'S BEACHSIDE MOTEL
COCOA BEACH, FLORIDA
OCTOBER 2-4, 1979

Conversion Factors for English and Metric Units
To convert
To convert
column 1
column 2
into column 2,
into column 1
multiply by Column 1
Column 2
multiply by
LENGTH
0.621
kilometer, km
mile, mi
1.609
1.094
meter, m
yard, yd
0.914
0.394
centimeter, cm
inch, in
2.54
AREA
0.386
kilometer2, km2
mile2, mi2
2.590
247.1
kilometer2, km2
acre, acre
0.00405
2.471
hectare, ha
acre, acre
0.405
VOLUME
0.00973
meter3, m3
acre-inch
102.8
3.532
hectoliter, hi
cubic foot, ft3
0.2832
2.838
hectoliter, hi
bushel, bu
0.352
0.0284
liter
bushel, bu
35.24
1.057
liter
quart (liquid), qt
0.946
MASS
1.102
ton (metric)
ton (English)
0.9072
2.205
quintal, q
hundredweight,
0.454
cwt (short)
2.205
kilogram, kg
pound, lb
0.454
0.035
gram, g
ounce (avdp), oz
28.35
PRESSURE
14.22
kg/cm2
lb/inch2, psi
0.0703
0.9678
kg/cm2
atmospheres, atm
1.033
0.9869
bar
atmospheres, atm
1.013
YIELD OR RATE
0.446
ton (metric)/hectare
ton (English)/acre
2.240
0.892
kg/ha
lb/acre
1.12
0.892
quintal/hectare
hundredweight/acre
1.12
0.87
hectoliter/ha, hl/ha
bu/acre
1.15
TEMPERATURE
\
Celsius, C
Fahrenheit, F
T (F
C 1+32
, -17.8
oo
0
32
/
20
68
100
212

1979 OFFICERS
President: D. W. Jones
Agronomy Department, IFAS
University of Florida
President-Elect: V. W. Carlisle
Soil Science Department, IFAS
University of Florida
Secretary-Treasurer: J. B. Sartain
Soil Science Department, IFAS,
University of Florida
Gainesville, Florida 32611
Directors:
O. C. Ruelke (1979)
Agronomy Department, IFAS,
University of Florida
P. H. Everett (1980)
ARC-IFAS,
University of Florida,
Immokalee, Florida
F. M. Rhoads (1981)
AREC-IFAS, University ol
Florida
Quincy, Florida
EDITORIAL BOARD
Editor: E. S. Horner
Agronomy Department, IFAS,
University of Florida,
Gainesville
Associate Editor:
C. C. Hortenstine
Soil Science Department, IFAS
Published annually by the Soil and Crop
Science Society of Florida. Membership
dues including subscription to annual pro
ceedings are $10.00 per year. At least one
author of a paper submitted for publica
tion in the Proceedings must be an active
or honorary member of the Society except
for invitational papers. Ordinarily, con
tributions shall have been presented at
annual meetings; exceptions must have
approval of the Executive Committee and
the Editorial Board. Contributions may be
(1) papers on original research or (2) in
vitational papers of a philosophical or re
view nature presented before general as
semblies or in symposia. A charge of
$10.00 per printed page in the Proceedings
will be billed to the agency the author
represents to help defray printing costs.
Members are limited to senior authorship
of one volunteer paper per volume; there
is no limit for junior authorships.
THE SOIL AND CROP SCIENCE SOCIETY OF FLORIDA
PROCEEDINGS
VOL. 39 CONTENTS 1980
Dedication
Honorary Life Member vi
SYMPOSIUM
Native Range Land, A Low Energy Grassland Resource Lewis L. Yarlett 1
The Role of Improved Forage Crops in Livestock Systems O. Charles Ruelke 3
Soil Fertility Management for Improved Pastures William G. Blue 5
Integrating Native Range and Pasture E. R. Felton 8
Properties of Representative Peninsular Florida Soils Used for Range and Pasture
Victor W. Carlisle 9
SOILS SEGTION
Fruit Yield of Florida Belle Strawberries as Affected by Rates of a
Resin Coated Fertilizer E. E. Albregts and C. M. Howard 14
Copper Nutrition of Cucumber (Cucumis sativus L.) as Influenced by Fertilizer
Placement, Phosphorus Rate, and Phosphorus Source
A. A. Navarro and S. J. Locascio 16
Nitrogen Losses from Urea, Ammonium Sulfate, and Ammonium
Nitrate Applications to a Slash Pine Plantation
D. B. Boomsma and W. L. Pritchett 19
Profile Distribution of Phosphate and Metals in a Forest Soil Amended with
Garbage Compost J. G. A. Fiskell and W. L. Pritchett 23
Evaporation Effects on Sprinkler Irrigation Efficiencies
Allen G. Smajstrla and Richard S. Hanson 28
Soil-Water Characteristics of Histosols as Related to Water Table Depth
G. S. Rahi and S. F. Shih 34
Major Land Resource Areas in Florida R. E. Caldwell 38
Sulfur Fertilization of Corn Seedlings C. C. Mitchell, Jr. and R. N. Gallaher 40
The Response of the Three Perennial Warm-Season Grasses to Fertilizer
Nitrogen on Eaugallie Fine Sand (Alfic Haplaquod) in Central Florida
W. G. Blue, C. L. Dantzman, and V. Impithuksa 44
Mobility and Extractability of Phosphorus Applied to the Surface of Tifway
Bermudagrass Turf J. B. Sartain 47
Growth Responses of Young Slash Pine to Site Preparation and Fertilization on
Poorly Drained Soils W. L. Pritchett and E. G. Flaig 51
Corn Response to Nitrogen and Phosphorus in a Florida Ultisol for Simulation of
Field Fertilization Techniques Used in El Salvador E. Jacome and W. G. Blue 55
Growth and Cadmium Uptake by Lettuce and Radish Fertilized with Cadmium, Zinc,
and Sewage Sludge Charles C. Hortenstine 58
Genesis of Acid Sulfate Soils S. C. Hodges and V. W. Carlisle 62
Application of Ground Penetrating Radar to Soil Survey
R. W. Johnson, R. Glaccum, and R. Wojtasinski 68
Soil Characteristics and Their Relationship to Growth of Needlerush
Charles L. Coultas and Orion J. Weber 73
CROPS SECTION
Effect of Metalaxyl Fungicide (CGA 48988) on Blue Mold and Black Shank of
Tobacco Tom Kucharek, E. B. Whitty and John Taylor 78
Legume Covercrop Trials in Citrus Groves Carl A. Anderson 80
Vegetation in Areas Stripmined for Phosphate
Robert M. Craig and Donald C. Smith 83
Winter Hardiness in Limpograss, Hemarthria altissima A. J. Oakes 86
Reaction of Stylosanthes hamata (L.) Taub. Indigenous to Southeast Florida to
Colletotrcihum gloeosporioides (Penz.) Sacc.
R. M. Sonoda and J. B. Brolmann 88
Effect of Nematicides and Application Methods on Sting Nematode Control,
Root Nodulation, and Yield of Soybeans H. L. Rhoades 90
Forage Production From Pearl Millet Following Rye and Ryegrass Fertilized
With Sulfur-Coated Urea L. S. Dunavin 92

Rates of Decline in Productivity of Florida Sugarcane
Jose Alvarez, Gerald Kidder, Thomas H. Spreen, and Donald R. Crane, Jr.
Soil Temperature Related to Water Table Depth S. F. Shih and G. /. Gascho
Evaluation of Various Stylosanthes Accessions in South Florida
J. B. Brolmann
Factors that Influence Rural Land Prices in Florida
John E. Reynolds and Devin L. Tower
Determination of Optimal Levels of Field Crops, Forages, and Beef Cattle
Enterprises J. Walter Prevatt, John E. Reynolds, and Bryan E. Melton
Responses of Two Pearl Millets Grown in vitro After Inoculation with Azospirillum
brasilense S. C. Schank, Rex L. Smith and Glen C. Weiser
A Comparison of Insect Pest Populations in Natural and Chemically Treated
Plots of Alfalfa With and Without Irrigation
D. R. Minnick and O. C. Ruelke
Effect of Age of Bahiagrass Sod on Succeeding Corn Crops
A. J. Norden, V. G. Perry, F. G. Martin, and J. NeSmith
Effect of Herbicides Applied to Corn on Subsequent Tomato, Pepper, and
Cucumber Crops P. H. Everett, R. S. Kalmbacher, C. Chambliss, and D. FI. Teem
Nutrient Metabolism and Quality of Corn and Sorghum Silages Made with Caged
Layer Manure M. F. Richter and R. S. Kalmbacher
Factors Affecting Hydrocyanic Acid Potential of Ona Stargrass
E. M. Hodges, M. F. Richter, and F. G. Martin
Influence of Fungicides, Nematicides, and Tobacco Cultivis on Yield Losses
Due to the Black Shank-Root Knot Disease Complex
J. R. Rich, J. T. Johnson, and G. E. Sanden
Economics of Irrigating Peanuts
Timothy D. Hewitt, Daniel W. Gorbet, and George O. Westberry
Blue Mold Incidence in Tobacco as Affected by Nitrogen Fertilization
IT. D. Smith, E. B. Whitty, and T. A. Kucharek
Endomycorrhizal Fungus Infection in Citrus Fibrous Roots of Trees with
and without Blight S. Nemec
Aeschynomene spp.: Distribution and Potential Use
Albert E. Kretschmer, Jr., and Robert C. Bullock
Flowering Dates and Freeze Ratings of Cool-Season Forage Crops
in North Florida A. R. Soffes and G. M. Prine
SOCIETY AFFAIRS
Minutes of the Business Meeting
Banquet
Secretary-Treasurers Report
Honorary Life Members
Sustaining Members 1978 .
95
98
102
104
108
112
115
118
122
125
127
131
135
140
141
145
153
156
156
158
158
158

DEDICATION
Nathan Gammon, Jr.
Nathan Gammon, Jr., was born June 22, 1914, in
Cheyenne, Wyoming. His early childhood was spent in
Helena, Montana, and his teenage years in Washing
ton, D.C.
He majored in chemistry at the University of Mary
land and was awarded a Bachelor of Science degree in
1956. Following graduation, he worked for two years
as an Assistant in Agronomy (Chemist) at the Uni
versity of Maryland and was awarded a Master of Sci
ence in the area of soil chemistry in 1959.
In the summer of 1958, he went to the Ohio Agri
cultural Experiment Station at Wooster, Ohio, as a
half-time Assistant in Corn Investigations and gradu
ate student at Ohio State University. He was awarded
the Doctor of Philosophy degree from that institution
in 1941 with a major in soils and minors in chemistry
and plant physiology.
After one more year of full-time research at Wooster,
he was commissioned an Ensign in the United States
Naval Reserve and served on active duty in the Bureau
of Ordnance, Pyrotechnic Section, until released from
active duty as a Lieutenant, senior grade in December,
1945. While on active duty in the Washington, D.C.
area, he took advantage of the opportunity to take post
doctorate courses in the U.S.D.A. Graduate School.
Dr. Gammon joined the University of Florida staff
in January of 1946 as Soil Chemist and Professor of
Soils, a position in which he was held in high regard
until his retirement as Professor Emeritus in 1979.
His research career may best be described as a love
for the scientific with a close eye for the practical.
Some of his early studies on the potassium require
ments for white clover and other legumes led to co
operative studies with Dr. Win. G. Blue which changed
the 0-14-14 fertilizer recommendations for legume
pasture to 0-10-20 and 0-10-50 ratios that more nearly
meet the plant requirements. He worked with Dr.
Gaylord M. Volk in establishing the need for nitrate
nitrogen for potatoes, supplied either as fertilizer or
by soil pH adjustment that would insure rapid nitrate
production from ammoniacal forms of nitrogen. Dr.
Volk was again his coworker in a study of molybdenum
deficiency of cauliflower and other crops.
Dr. Gammon has always had an eye for beauty,
hence one of his first publications from Gainesville
was on the effect of pH on camellia growth; his last
was on a nutritional problem associated with rose root
stocks. Likewise, his feeling that agriculture should care
for the inner man intensified his nutritional studies
on pecans, peaches, and other fruits. His many publica
tions in the area, as well as an intense personal interest,
have made him a recognized national authority in the
area of pecan nutrition. The Florida and the South
eastern Pecan Growers Associations count him as an
active member.
During the 1970s, he taught an undergraduate
course in soil chemistry and a graduate course in micro
nutrients. He also directed students in a number of
Master and Doctor of Philosophy programs. His teach
ing was characterized by stressing the relationship of
scientific truths to practical results and an insistence
on truth and accuracy always administered with kind
ness and compassion.
While serving as President of the Soil and Crop
Science Society of Florida, Dr. Gammon appointed the
first editor of the Proceedings. This new appointment
resulted in the publication of the 1955 Proceedings on
time and the publication of all back issues within the
next two years.
Dr. Gammon was elected a Fellow of the American
Association for the Advancement of Science in 1940.
He was honored in 1955 by best paper awards in both
the Soil Science Society of Florida and the Florida
State Horticultural Society. In addition to these three
societies, he was also a member of the American Chem
ical Society, the American Society of Agronomy, the
Soil Science Society of America, and the University of
Florida Athenaeum Club. A number of research and
professional societies also elected him to membership
including Sigma Xi, Alpha Chi Sigma, Phi Lambda
Upsilon, Gamma Alpha, Phi Epsilon Phi, and Gamma
Sigma Delta.
The Soil and Crop Science Society of Florida, in
recognition of his many contributions to soil and plant
science in Florida, both in teaching and research, as
well as his many years of service to the Society as an
active member and as Associate Editor of the Proceed
ings, is pleased to dedicate Volume 59 of its Proceed
ings to Dr. Nathan Gammon, Jr.

HONORARY LIFE MEMBER
Gordon Beverly Killinger
In recognition of his many contributions to agri
culture and to the success of this Society, Gordon
Beverly Killinger has been selected to honorary life
time membership in the Soil and Crop Science Society
of Florida.
Dr. Killinger was born December 31, 1908, at Elliot,
Iowa. He earned his Bachelor of Science degree in
1930, his Master of Science degree in 1931, and the
Doctor of Philosophy degree in 1933. All degrees were
awarded by Iowa State University. The major for his
terminal degree was Soil Fertility and the minors were
Chemistry and Soil Bacteriology. After completion of
his formal education, Dr. Killinger was employed by
Federal Land Bank of Omaha. In 1934, he joined the
Soil Conservation Service at Mankato, Kansas and
completed the first soil erosion and land use maps of
Kansas and South Dakota.
In 1936, Dr. Killinger joined the faculty of Clemson
College, where he developed and taught the first pas
tures course offered at that institution. He also taught
other courses in forage and cover crops. He came to the
University of Florida in 1941 where he served as Agron
omist and Professor of Agronomy until his retirement
in 1975.
A large portion of Dr. Killingers professional career
was spent in the development of improved pastures.
His influence on pasture improvement in the South has
been considerable and he has numerous publications
on related subjects. He was a member of the teams that
developed and released Pangolagrass and Pensacola
Bahiagrass, which currently account for more than 3
million acres of pasture in the southern United States.
He made significant contributions to forage improve
ment through the breeding and release of Argentine
bahiagrass and Floranna White sweetclover.
From 1955 to 1957, Dr. Killinger served as Agron
omy Advisor and developed a pasture and forage pro
gram in Costa Rica, under a Florida ICA-STICA con
tract. In this program, he helped introduce Pangola-
grass and Coastal bermudagrass along with Louisiana
white and Kenlancl reclclover, which became popular
forages in that country. For his contributions to that
countrys agriculture, Dr. Killinger received a Costa
Rican award for outstanding research and develop
ment.
Returning to the University of Florida in 1957, Dr.
Killinger was appointed to serve on the Southern
Regional Technical Committee for new crops. Most of
the remainder of his active research career was spent
in evaluating new crop plants.
Dr. Killinger made significant contributions in the
area of agronomic instruction. In addition to organiz
ing and teaching courses at Clemson University, he
taught the course in Pasture Science at the University
of Florida. The pattern of instruction that he devel
oped was adopted by subsequent teachers of that
course. Dr. Killinger directed the graduate programs
of three doctoral students in Agronomy, as well as four
students in a Master of Science program.
Many awards have been bestowed upon Dr.
Killinger for his numerous contributions, and he has
served in many professional organizations. He was
elected a Fellow in the American Society of Agronomy
in 1962. He served as President of the Southern Branch
of the American Society of Agronomy in 1966, as well
as President of the Soil and Crop Science Society of
Florida in 1967. In recognition of his service to agri
culture, this Society dedicated their Proceedings, Vol
ume 38, to him in 1978. Dr. Killinger was also Chair
man of the Southern Pasture and Forage Conference in
1958. He has held membership in the American Society
of Agronomy, Crop Science Society of America, Soil
and Crop Science Society of Florida, and Southern
Agronomy Workers Association, as well as Sigma Xi,
Gamma Sigma Delta, and Alpha Zeta.
Well-known nationally and internationally, Dr.
Killinger has responded generously to the demands
placed on him. He enjoys an outstanding reputation as
a pasture scientist.
For his many contributions to the improvement of
forage and pasture production as well as his service to
this Society, the membership of the Soil and Crop Sci
ence Society of Florida is pleased to elect Dr. Gordon
B. Killinger as honorary life member.

SYMPOSIUM
Native Range Land,
A Low Energy Grassland Resource
Lewis L. Yarlett1
The United States, with only 6 percent of the
worlds population, uses over one-third of the worlds
energy. One-hundred percent of the U.S. population
has, through the media of radio, tv, and the press,
been informed of the fossil fuel energy crisis. Grassland
agriculture in Florida has for the past decades utilized
abundant, inexpensive energy for the production of
livestock forage. The major percentage of production
has come from improved pasture programs, which has
required large inputs of both fossil fuels and labor.
Increased recognition of proper use and management
of the native range resource can materially reduce the
amount of energy required by the Florida cattle in
dustry.
Range management is both an art and a science
founded on ecological principles. It deals with the
management of native grasslands and understory vege
tation on grazeable forestland. A basic factor in range
ecology is plant succession, the process by which plants
succeed other plants. Cattle are very selective grazers.
The most palatable grasses are those that are readily
selected and are replaced by less desirable species. The
key that controls the process is the rancher or manager
who knows his vegetation and can manage these re
sources.
Range forage is a combination of native species in
cluding grasses, grass-likes, legumes, and other forbs.
In one sense of the word it is a crop. It is a crop that
can be successfully grown. Range forage can be suc
cessfully managed. Harvesting is no problem. Cattle
can efficiently and economically harvest range forage.
The growing, management, and harvesting can be done
with the lowest possible input of energy of any grass
land enterprize.
Beginning with the Arab boycott early in 1974,
shortages of fossil fuel energy were felt by all segments
of our economy. The availability of fossil fuels in the
future will be critical. Agriculture has been indicated
as one industry likely to receive some priority for
needed food production.
Current beef production in Florida during the past
25 to 30 years has used high inputs of fossil fuel. Large
acreages of native range were converted to pasture and
maintained. Many pastures in south Florida were de
signed for irrigation and water control. In the not too
distant future water for pasture irrigation may be pro
hibitive due both to cost as well as legislatively estab
lished priorities. Many warnings have been issued of a
serious water quality problem and shortage in several
areas in south Florida.
Any present-day attempt to analyze the exact energy
cost of a grassland management program, either pasture
or range, is likely to be outdated within weeks. It is
difficult to gather the required data, prepare a sum
mary, and publish before the entire price structure
changes.
i Biologist, Range Ecosystem Management, School of Forest
Resources and Conservation, Institute of Food and Agricultural
Sciences, University of Florida, Gainesville, Florida.
In 1973 gasoline cost approximately .$0.40/gal
($0.11/liter) and diesel fuel $0.20 to 0.25/gal ($0.06/
liter). Converting flatwoods range to irrigated pasture
cost approximately $60 to 70/acre ($150 to 170/ha) in
1973 with an annual operating expense of about $10/
acre ($25/ha) (Hipp, 1974). Present day prices indicate
establishment costs of $200/acre ($500/ha) or more.
The 1978 cost of a complete 16" x 1300' (40 cm x 400
m) well was $35,000.2
Unfortunately, the bottom line is that production
of forage from improved pastures remains at very much
the same level in 1980 as it was in 1973. Production
and maintenance costs mandate that a low energy
grassland program circumvent the use of fertilized grass
to produce hay or to maintain brood cows on pastures.
From an economic as well as from a physiological
standpoint, improved pastures have only a specific use.
Pastures are best utilized as a breeding ground and to
produce beef and not to maintain the cow.
The range resource is easily managed and a logical
alternative for the development of a low energy grass
land program in Florida. It has been estimated that
8.4 to over 12 million acres (3.4 to 4.8 million hectares)
have the potential for management to produce forage
for livestock and improved wildlife habitat. This in
cludes range, commercial, and non-commercial forest
lands. A basic fact must be recognized. Experiences of
commercial producers indicate that coordinated pro
grams utilizing both pastures and range resources are
successful.
Many species of grasses, grasslikes, legumes, and
other forbs are present and are able to withstand ex
tremes of wet and dry. The extremes of heat and cold
induce only natural functions of plant growth. Insects
and disease are practically unknown to curb growth or
production. Depending upon the degree of manage
ment applied, production of a native forage resource
is variable. Unmanaged flatwoods in poor condition
produce 600 to 1200 pounds of forage per acre (670 to
1,340 kg/ha), useable for 6 to 8 weeks (White, 1973).
This has been commonly termed wiregrass manage
ment. On the other side of the ledger, with planned
management, 2,000 to 8,000 pounds of air dry forage
per acre (2,240 to 9,000 kg/ha) is available for utiliza
tion over a period of 6 to 9 months. Successful pro
ducers, utilizing both pastures and range with a
planned grazing system, average 4 to 6 months on
range and 6 to 8 months on pasture. Four thousand
pounds per acre (4,500 kg/ha) green weight of creep
ing bluestem (Schizachyrium stoloniferum Nash)
has been produced in an 11-month period on ranches
where palmetto was being mechanically controlled
(Yarlett, 1965). An additional 1,500 pounds per acre
(1,700 kg/ha) was produced by other desirable species.
Current research at the Ona Research Center indicates
creeping bluestem as a major species following pal
metto control, and comparable levels of production
(Kalmbacher, 1979).
^Personal communication with producers.

2
Soil and Crop Science Society of Florida
Marsh ranges are the most productive. Production
from maidencane can be expected to produce as much
as 8,000 pounds per acre (9,000 kg/ha) air dry. Re
search by White (197S) indicated 9,900 pound per
acre (11,000 kg/ha), air dry following one full growing
season after several years of heavy grazing. Research
is continuing on the productive potential of fresh
marshes dominated by maidencane.
The comparative energy inputs to manage ranges
are few compared to those for managing improved
pastures (Figs. 1 and 2). Many energy costs recur an
nually on pasture and require high inputs of fossil
fuel. Fertilizer production is related to the current
shortages of natural gas needed to produce basic
nitrogenous fertilizer material. Many economists have
predicted a substantial increase in fertilizer costs the
next three years.
Energy requirements for range improvement and
management are not prohibitive in light of present day
costs. The following preliminary costs were obtained
from feed producers, ranchers, and contractors. Pal
metto control is required on most flatwood ranges to
obtain maximum production. A D-7 catapiller pulling
the heavy marden chopper averages 8.7 gals/hr (33
liters/hr) diesel fuel. At a cost of $1.0/gal ($0.26/liter)
this amounts to $3.48/acre ($8.60/ha) for fuel. This
cost will amortize at $0.71 per acre ($1.75/ha) over a
period of seven years at 10 percent interest. A web
plow, with a lower fuel consumption of 8 gals/hr (30
liters/hr) and covering 30 acres (12 ha) per 8 hour day
is reported to cost slightly less.
Supplementation is essential for the utilization of
native range forage (Terry, 1979). A 32% protein
liquid supplement with urea sold for $135/ton ($150/
metric ton) in December 1979. Average consumption
per 1,000 pound (450 kg) brood cow is estimated at
2 lb/day (0.91 kg). Supplementation for a 180-day
grazing period, October 1 to April 1, on bluestem range
equals a cost of $24 per cow. Supplementation may
well be the most profitable outlay in a range program
to utilize the high volume of forage produced from
well-managed ranges.
There are benefits to be obtained from a combina
tion range management-pasture program. Recovery
and growth of native species is fast. Results from man
aging flatwood and marsh ranges can be expected in
12 months. One high-producing commercial operation
initiated such a program in 195821 years ago. An
other began in 1963 and has operated successfully since
then. There are others, both large and small, that have
initiated programs using a minimum acreage of pasture
for breeding grounds and growing the calf up to
market age and weight. Other benefits may be listed as
follows:
(a) Contributes to higher conception rates when
cows are moved from range to green pasture in
the spring.
(b) Range experience and research indicates a
longer life span for brood cows.
(c) Pasture rotations with rests of 30 days or more
break the life cycle of some species of parasites.
(d) Good quality range is ideal for dry cows.
(e) Good range provides for emergency forage dur
ing extreme wet or dry periods.
(f) Increased benefits from wildlifeespecially quail
and turkey.
(g) Labor costs are lower on high quality ranges.
(h) Energy costs are reduced.
Fig. 1.Comparative energetics of an acre of improved pasture
for 1973-1979. Unquantified inputs and products are shown in
white for 1973 and in black for 1979. Forage production remains
essentially the same with possible slight reductions. (Adopted
from An Analysis of Cattle Ranching in the Kissimmee River
Basin. Ecoimpact Inc. 1976.)
Fig. 2.Comparative energetics of an acre of native range.
Unquantified inputs and products are shown in white for 1973
and black for 1979. (Adapted from: An Analysis of Cattle
Ranching in the Kissimmee River Basin. Ecoimpact Inc. 1976.)
SUMMARY
Large inputs of energy have been profitable in the
past, since improved pasture techniques and practices
were developed and recommended under low energy
costs of yseterday prices. Production of forages with a
minimum input of energy is now essential. Present
realities appear to preclude continued neglect of
underrated range resources. The economics of energy
appear to dictate that ranching in Florida be brought
into balance with low-energy production methods. The
cattle cycle appears to operate on a seven year cycle
with highs and lows of both numbers and prices. High
producing ranges will fit any place in that seven year
cycle.
Ranchers with a high percent of their land in im
proved pastures have narrowed their flexibility and
now depend on energy subsidies, and the relationships
between energy and fertilizer costs will have drastic
repercussions on cattlemen who maintain improved
pasture. Cattlemen now contemplating the conversion
of more native range to improved pasture would be

Proceedings, Volume 39, 1980
well advised to consider the future costs of fertilizers,
equipment, fuel, and labor compared to benefits from
well managed and productive ranges.
LITERATURE CITED
Anderson, C. L., and T. S. Hipp. 1974. Requirements and re
turns for 1000-cow beef herds of flatwood soils in Florida.
Coop. Ext. Ser., Univ. of Fla. Circular 385.
Kalmbacker, R. IS. 1979. Submitted manuscripts for publication.
J. Range Manage.
Terry, W. S. 1979. Nutritive value of some Florida range grasses.
3
Proceedings, annual meeting, Southern Section Society for
Range Management. Sarasota, Fla.
White, L. D. 1973. Native forage resources and their potential.
Range resources of the Southeastern U.S. American Society
Agronomy special publication No. 21. pp. 1-17.
. 1973. Ecosystem analysis of Paynes Prairie. School of
Forest Resources and Conservation. Research Report #24.
Inst, of Food and Agri. Sciences. Univ. of Fla.
Yarlett, L. L. 1965. Control of saw palmetto and recovery of
native grasses. J. Range Manage. 18:344-345.
. 1969. Creeping bluestem [Andropogon stolonifer
(Nash) Hitch.]. J. Range. Manage. 23:117-122.
The Role of Improved Forage Crops in Livestock Systems1
O. Charles Ruelke2
What has happened to land use and what can we
anticipate in the near future? From data published in
Agricultural Statistics 1978 (9), grassland pastures in
the United States decreased from 633 million acres in
1959 to 598 million in 1974, while cropland used for
pasture increased from 66 million acres to 83 million
acres in the same period of time. Since then, data
gathered for the AGUA Report (8) in 1974, and pro
jected for 1985, indicated that total acreage of grass
lands of Florida would decrease by four percent. The
greatest decrease would be in range pastures and wood
land pastures, while improved pastures were expected
to increase by 10 percent. Land area used for improved
pastures in Florida was estimated at 3.1 million acres
in 1974 and is projected to increase to 3.4 million by
1985 (8). Land use for production of hay and silage
was expected to increase 20 and 83 percent respectively,
by 1985. According to the best information available,
Florida is well along the way toward fulfilling these
projections.
How important are forages in livestock systems?
The value of cattle and calves on farms and ranches of
the U.S. on January 1, 1979, went up to $44.7 billion,
65% greater than a year earlier (10). In Florida, dur
ing 1978, 26.3% of total agricultural sales was from
livestock and livestock products (10). Because forages
make up a major part of the feed requirements of live
stock, the value of forages was estimated to exceed
$428.7 million in Florida during 1978.
What are improved forage crops and where do they
originate? Examples of improved forage crops date
back to the introduction of Dutch White Clover by the
early colonists from Europe in the 1600s. Since then
common bermudagrass from India, common bahiagrass
from Cuba, digitgrass and limpograss from Africa, as
well as many tropical legumes from Central and South
America and other tropical areas, are examples of
introduced improved forage species. However, from
these introductions a considerable amount of testing,
breeding, selection, hybridization and evaluation has
been necessary to find species which were adapted to
iSymposium presentation at Joint Session of Florida Chapter
American Society of Range Management and Soil & Crop Science
Society of Florida 39th Annual Meeting, October 2, 1979, at the
Brevard Agricultural Center, 1125 W. King Street (SR 520),
Cocoa, Florida.
2Professor of Agronomy, Department of Agronomy, University
of Florida, Gainesville, Florida 32611.
the widely variable environments found in the USA
and especially in Florida. Production and performance
data at various locations can be obtained from State
Agricultural Experiment Station Reports (3) and have
contributed significantly to the selection of the best
adapted species and cultivars. Because of the great
diversity of climate and soils in Florida, species suited
to one location may not be suitable to another. Specif
ically, climate in North and Northwest Florida may be
characterized as temperate as a result of the cold fronts
and frequent periods when temperatures may remain
below freezing for more than a day at a time. Likewise,
many areas along the lower East and West coast of
Florida have more sub-tropical climate where frost may
not occur for periods of years.
Rainfall may vary from less than 40 inches per year
to over 60 inches per year with North and South Flor
ida having generally more rainfall, and Central Florida
less rainfall.
Soils of Florida also vary from the most productive
organic muck soils to almost completely sterile beach
sand. Obviously, the species and varieties of improved
forages will greatly differ from one location to another.
What then are the basic criteria necessary for select
ing improved forage species and cultivars for a specific
location? Probably temperature, extremes and dura
tions, should be considered first in selecting improved
forages species for an area because they have a com
manding effect on the production and quality of
forage. Because there is little we can do to control the
temperature, we must resort to species which perform
best under the prevailing temperatures.
Within any location in an area, moisture is prob
ably our second consideration. Although we cannot
stop rainfall we can add water by irrigation, if an
adequate supply of water is available.
Likewise, soil fertility ranks next in importance in
selecting an improved forage species for a specific site.
Fortunately, as a result of soil testing and previous ex
perience, it is possible to determine if and what soil
amendments can and must be used in order to estab
lish a specific improved forage crop. For example,
alfalfa and sweetclover require a pH range of 6.5-7.0
and a minimal CaO and MgO of 1200 and 100 Ibs/A
(1344 and 112 kg/ha) respectively, while true clovers
require pH 6.0-7.0 with CaO and MgO levels of 900
and 100 Ibs/A (1008 and 112 kg/ha) respectively.
Forage grasses require pH 5.5-6.5 with CaO and MgO

4
Soil and Crop Science Society of Florida
levels of 600 and 100 Ibs/A (672 and 112 kg/ha) re
spectively (11). Medium levels of P205 and KoO re
quired for improved forages on sandy soils of Florida
range from 81-140 lbs/A (91-157 kg/ha) and 91-150
lbs/A (102-168 kg/ha) respectively (12).
Will it pay to establish and produce improved for
ages? Numerous studies throughout the USA have re
searched this question. In Florida, the results from two
major independent studies (4, 5, 6, and 7) have shown
that improved grass-clover pastures greatly increased
the percentage calf crop, percentage of calves weaned,
calf weaning weights, calf grades, price per pound,
pounds of calf weight per cow and pounds of calf per
acre over that produced as straight grass alone or on
present native vegetation. As population increases,
natural grassland acreages decrease and taxation con
tinues to increase, it will be necessary to shift from an
extensive to a more intensive type of land use and man
agement. Although costs of inputs continue to increase
on both unimproved and improved grasslands, in
creased pressure from land use and increased return
per dollar invested in improvement will most likely
come from the improved forages.
What basic principles should be observed in man
agement of improved forage crops? The management
we apply to improved forages differs with the species,
growth habit, and stage of growth. Generally, grasses
like bahiagrass, carpetgrass, St. Augustine grass, and
legumes like white clover and subclover can be con
tinuously close grazed or harvested in order to get the
major portion of the forage available without severe
reduction in regrowth or stands. Grasses such as cool
season cereals (like oats or rye), warm season annuals
(like pearl millet and sorghums), and some perennial
erect tall growth grasses (like limpograss or napier-
grass), must be allowed to acumlate substantial
amounts of topgrowth before grazed or harvested fol
lowed by a sufficient rest period for regrowth. For these
species, and many of the erect winter and summer
legumes, rotational grazing is required in order to
achieve full yield potential and satisfactory persistence.
Deferring grazing, or harvesting, is extremely impor
tant while new plantings are getting established as well
as being a means of stockpiling forage during periods
of abundance (such as during the late summer), for
periods of shortages during the fall and early winter.
High quality forage like rye, ryegrass, or clover can be
used to supplement poor quality frosted bahiagrass or
native grasses. However, you must plan ahead to supply
your needs.
What basic principles should be observed in fer
tilization of improved forage crops? Before you estab
lish improved forage crops there must be a need for
the forage. If there is a need for the forage you must
provide the minimum fertilizer requirement of that
forage crop. You cannot make something out of noth
ing and forage crops cannot produce high yields of
quality forage without sufficient amounts of the es
sential elements. Fertilize forage crops when and where
the forage is needed. The optimum rate will be deter
mined by the dollars in forage value returned per
dollar spent for fertilizer on a specific species on a
specific location. Improved forage species are bred and
selected for increased efficiency in returning more for
age per dollar spent for production. When growing
legumes with grasses one can generally fertilize to favor
the legume (like clover) and the grass (like bahiagrass)
will take care of itself.
What role have unproved forages played in the in
crease in liveweiglit gains of forage feed cattle on the
sandy soils of southeastern USA? In a recent thought-
provoking article by Burton (2) he pointed out that, in
1860, cattle on native range averaged 4-8 pounds of
liveweight gain per acre (4.5-9 kg/ha) per year, while
in 1930 gains on common bermudagrass were 80 #/A
(90 kg/ha). In 1970 gains on Coastal bermudagrass
with 140 #/A (156 kg/ha) of N plus P and K were
485 #/A/yr (543 kg/ha). Further genetic improve
ment resulted in Coastcross-1 bermudagrass which
with 140 #/A (156 kg/ha) of N plus P and K, pro
duced 745 #/A/yr (834 kg/ha) of liveweight gain.
Today fertilized Coastcross-1 grazed with rye or rye
grass grazed has resulted in 1000 #/A/yr (1120 kg/ha)
gains in tests in Georgia. With a 12-month growing
season on fertilized organic soils in South Florida, beef
gains of over 2000 lbs/A (2290 kg/ha) have been re
ported for seven consecutive years (1).
In the future, with twelve months of the year pro
ducing improved forages, supplemented with addi
tional sources of feeds which are readily accessable,
fed to hybrid animals with stimulated appetites, is it
¡possible to produce 6000 # (6720 kg/ha) of beef/year
on one acre of land?
SELECTED LITERATURE CITED
1. Bair, R. A., and R. W. Kidder. 1946. Pasture investigations
on the peat and muck soils o£ the Everglades. Fla. Agr. Expt.
Sta. An. Rpt. pp. 180-181.
2. Burton, G. W. 1972. Can the South become the worlds great
est grassland? Prog. Farmer. 87:(3), pp. 22-24.
3. Dean, C. E. 1979. Florida field and forage crop variety re
port-1978. Agron. Res. Rpt. AG 79-5, IFAS Agr. Exp. Sta.
and Coop. Ext. Serv., Univ. of Fla., Gainesville, Fla. 90 p.
4. Roger, M., et al. 1961. Beef production, soil and forage
analysis, and economic returns from eight pasture programs
in North Central Florida. Fla. Agr. Exp. Sta. IFAS Bull.
631 (t) 76 p.
5. Roger, M., et al. 1970. Production response and economic
returns from five pasture programs in North Central Florida.
Fla. Agr. Exp. Sta. IFAS Bull. 740(t) 45 p.
6. Roger, M. 1977. Pasture programs and beef cattle breeding
systems for beef production in North Central Florida. Fla.
Agr. Exp. Sta. IFAS Bull. 789(t) 47 p.
7. Peacock, F. M., et al. 1976. Forage systems, beef production,
and economic evaluations, South Florida. Fla. Agr. Exp. Sta.
Bull. 783(t) 14 p.
8. Pierce, J. B. 1975. Agricultural growth in an urban age.
Institute of Food and Agricultural Sciences. Univ. of Fla.
230 p.
9. U.S.D.A. 1978. Agricultural statistics 1978. U.S. Govt. Print
ing Office, Washington, D.C. 605 pp.
10. U.S.D.A. 1979. Florida cash receipts from farming. Fla. Crop
and Livestock Reporting Service USDA, Fla. Dept, of Agri.
and Univ. of Fla. Agri. Exp. Sta. 2 p.
11. Whitty, E. B., et al. 1977. Liming for production of field and
forage crops. Agronomy Facts:69 Fla. Coop. Ext. Serv. IFAS,
Univ. of Fla. 4 p.
12. Whitty, E. B., et al. 1977. Fertilization of field and forage
crops. Agronomy Facts:70 Fla. Coop. Ext. Serv. IFAS, Univ.
of Fla. 13 p.

Proceedings, Volume 39, 1980
5
Soil Fertility Management for Improved Pastures1
William G. Blue2
ABSTRACT
Nutrient requirements for intensive forage crop
production are similar to those for soybean and corn.
On Floridas acid, infertile mineral soils, judicious
liming and micronutrient fertilization should precede
application of macronutrients because of the potential
for A1 toxicity, Mg deficiency, micronutrient deficien
cies, and losses of macronutrients through leaching.
Forage production and N content of white clover-
grasses without fertilizer N have been comparable to
those from perennial grasses fertilized with 224 to 448
kg of N/ha annually. Beef production from legume-
grass pastures generally exceeded that from grass pas
tures at N rates through 134 kg/ha/year. The po
tential for substitution of symbiotically-fixed N by
legumes for fertilizer N was emphasized. Lime and fer
tilizer costs per kg of beef, at current prices, are $0.51
for the grass and for the legume-grass pasture, less than
$0.18. For successful production of legume-grass pas
tures, management must be more precise and consistent
than for grass pasture. Soil acidity must be corrected
by liming, micronutrient levels must be maintained,
and P and K must be applied at least annually.
Additional Index Words: Lime, Micronutrients,
Nitrogen, Legumes, Fertilizer costs, Beef production,
White clover, Trifolium repens L.
Floridas mineral soils are derived from relatively
coarse-textured, highly weathered materials. Most of
the virgin soils are acid and extremely infertile. Toxic
quantities of soil solution A1 may be a problem and
deficiencies of N, P, and K are common. Calcium, Mg,
and S, and one or more of the micronutrientsFe, Mn,
Zn, Cu, B, and Momay be deficient at or soon after
initiation of cultivation and cropping.
In considering the potential for production of
forage and cattle on these soils, one needs to under
stand that their productive capacity was very low in the
virgin condition. Protein, energy, and essential in
organic nutrients in forages from these soils were de
ficient for cattle. While some of the improved forage
plants, notably some of the grasses, will survive under
minimal levels of nutrition, intensive forage produc
tion requires nutrient levels similar to those required
by agronomic crops (Table 1).
For sustained production on most of our mineral
soils, the soil as a source of nutrients, without lime and
fertilizers, can almost be ignored. Exceptions are N, S,
and some of the micronutrients. Small amounts of N
and S are mineralized from soil organic matter, and
some of both are brought down by rain from con
taminants in the air. Small additional amounts of N
appear to be fixed by blue-green algae and hetero-
trophic microorganisms. Some soils have reasonable
supplies of micronutrients, but for intensive produc-
iFlorida Agricultural Experiment Stations Journal Series No.
2249.
^Professor (Soil Chemistry and Fertility), Soil Science Depart
ment, Florida Agricultural Experiment Station, Gainesville, FL
32611.
TABLE 1.Nutrient contents of soybean, corn, and Pensacola
BAHIACRASS.
Crop
Soybeans! Corn:|: P. bahiagrassjj
Nutrient (3,020 kg/ha) (9,410 kg/ha) (11,200 kg/ha)
Nutrient contents of above-ground portion, kg/ha
Nitrogen (N)
448
190
174
Phosphorus (P)
45
39
26
Potassium (K.)
280
196
112
Calcium (Ca)
101
40
56
Magnesium (Mg)
65
44
45
Sulfur (S)
28
21
34
Iron (Fe)
2.6
2.1
0.9
Manganese (Mn)
0.7
0.3
0.2
Zinc (Zn)
0.4
0.3
0.2
Copper (Cu)
0.1
0.1
0.1
Boron (B)
0.1
0.2
0.2
Molybdenum (Mo)
0.01
0.01
0.01
'¡'Nitrogen in soybean is obtained primarily by symbiotic fixa
tion. Data were taken from Smith, Hutton, and Robertson (1968).
Data were taken from Barber and Olson (1968).
{¡Data were taken from Blue (1971).
tion systems, these usually require supplementation.
By far the largest quantities of nutrients must be sup
plied through lime and fertilizers.
The costs of these nutrients have increased mark
edly in the 1970s as a consequence of increased energy
costs. Current costs of fertilizers necessary to supply the
nutrients in Pensacola bahiagrass (Paspalum notatum
Flugge) forage at a production level of 11.2 metric
tons/ha (5 tons/acre) are shown in Table 2. Nutrient
contents were determined in harvested forages. Nutri
ent requirements of other improved grasses do not vary
appreciably from those for bahiagrass. Because ade
quate lime of the correct kind to maintain the opti
mum pH and Ca and Mg balance is relatively inex
pensive compared with the macronutrientsN, P, and
Kcorrect liming must have the highest priority. The
TABLE 2.Nutrient contents of Pensacola bahiagrass and
COSTS of lime and fertilizers required to supply these nutrients.
Nutrient
Quantity!
Cost!
kg/ha
$/ha
Nitrogen
174
124
Phosphorus
26
30
Potassium
112
30
Calcium
56 )
Magnesium
45 f
7.4
Sulfur
34

Iron
0.9
Manganese
0.2 'i
Zinc
0.2 /
Copper
0.1 [
2.5
Boron
0.2 (
Molybdenum
0.01 \
fBased on 11.2 metric tons/ha (5 tons/acre) oven-dry forage
yield. Fertilizer nutrients required exceed plant contents because
of nutrient leaching and other loss mechanisms. Prices were
calculated on basis of USDA Publication FS9, 1979 Fertilizer
Situation, Oct. 15, 1978. These prices will depend on fertilizer
formulation, quantity purchased, and other services provided by
the fertilizer dealer.

6
Soil and Crop Science Society of Florida
cost of micronutrients is also relatively small and these
should be applied initially to correct potential deficien
cies.
FERTILIZER N FOR GRASS PASTURE
Nitrogen, which is required in largest quantity and
at highest cost, is the driving force for forage produc
tion. Requirements for other nutrients are propor
tional to the supply of N. Pensacola bahiagrass forage
production in response to rates of fertilizer N on a
Spodosol (poorly drained flatwoods soil) and an
Entisol (well-drained, deep sandy soil) are shown in
Fig. 1. Growth response was linear through the 224
kg/ha N rate on both soils. The data should apply well
to soil-plant systems where hay is harvested. There is
some recycling of all nutrients under grazing, but the
magnitude of N reutilization has not been established.
Total forage production from the Spodosol varied
from 120 kg/ha for each kg of N at the current average
N fertilization rate of 45 kg/ha/year to 34 kg for each
kg of N at the 448-kg/ha N rate. Dry matter for each
kg of N from the Entisol varied from 77 to 28 kg for
N rates from 0 to 448 kg/ha/year (Table 3). The
seasonal distribution of grass forage production varies
in different parts of the state due to temperature varia
tions and soil types, particularly as related to moisture
supply. Thus, grass forage production will occur over
Fig. 1.Growth Response of Pensacola bahiagrass to fertilizer
nitrogen on a Spodosol (poorly drained flatwoods) and on an
Entisol (well-drained ridge).
TABLE 3.Pensacola bahiagrass growth response to fertilizer
NITROGEN.
N
applied
Spodosol
Entisol
Forage yields
Forage yields
kg/ha
kg/ha
per kg of N
kg/ha
per kg of N
0
2,950

1,530

45
4,780
120
3,080
77
112
7,290
73
5,170
52
224
10,790
54
8,030
40
336
13,430
45
10,100
34
448
15,220
38
11,390
28
approximately 6 to 8 months on the Spodosol, but
usually for not more than 4 or 5 months on the Entisol
due to location in the state and drought conditions in
the spring. With judicious management, grazing can be
extended for 2 additional months during the fall for
both soils by utilizing mature forages. However, some
supplemental foragehay or silageis required to
maintain animals in suitable condition for reproduc
tion and calf growth, both of which are required for
intensive animal production.
FORAGE REQUIREMENTS FOR BEEF CATTLE
Forage and nutrient requirements for cattle vary
with age and expected performance. However, an
average value for forage is 9.1 kg/animal/day; the an
nual requirement would be 3,320 kg/animal. There is
some wasted forage from grazing, perhaps as much as
30% under intensive forage production (Roger et al.,
1961). Thus, 1 ha of grass on the Spodosol fertilized
with 224 kg of N/year (Table 3) would produce
enough forage for three animals. Production would be
substantially less on the Entisol. Even with this level of
forage production, provision must be made for supple
mental grazing or feeding. Data from the Beef Re
search Unit, University of Florida, Gainesville indi
cate that sufficient corn silage for supplemental feed
ing of one animal can be produced on an additional
0.05 ha (Roger et ah, 1970). If the pasture were fer
tilized with only 45 kg of N/ha/year, forage produc
tion per ha would be substantially less and carrying
capacity would be reduced accordingly. Furthermore,
reproduction of cattle was a consistent problem with
grass pastures on Spodosols at the Beef Research Unit
(Roger et ah, 1961) regardless of fertilization rate even
though animals were supplemented with protein.
Forage and animal production under grazing are
shown for grass pastures on Spodosols at the Beef Re
search Unit (Table 4). Forage production was in
creased markedly by fertilization; however, weaning
percentages were relatively low. Beef (calf) production
per cow was relatively constant but production per
acre was increased. Fertilizer costs at present prices are
high in relation to the value of beef produced.
LEGUME-GRASS PASTURES
A viable alternative to grass with N fertilizer is
legume-grass pasture. Legumes are capable of fixation
of atmospheric N through symbiosis with Rhizobium
bacteria. Legumes include those which grow well dur
ing the cool season and others which grow during the
TABLE 4.Production performance of cows on grass pastures
on Spodosols, Beef Research Unit.!
Fertilization
Annual
forage
production
Weaning
%
Beef production
N
P
K
Per ha
Per cow
kg/ha/year
kg/ha
kg
38
9
9
5,220
63
111
120
76
18
18
7,440
64
151
123
134
36
36
9,630
66
226
123
tGrasses were Pensacola bahiagrass, Pangla digitgrass (Digi-
taria decumbens Stent), and Coastal bermudagrass (Cynodon
dactylon L. Pers.). [Data were take from Roger et al. (1961).]

Proceedings, Volume 39, 1980
warm season. The legume that has been investigated
most extensively in Florida is white clover (Trifolium
repens L.) in mixture with Pensacola bahiagrass. This
legume is adapted to the Spodosols because of the fre
quent abundance of water and its relatively shallow
root system. White clover has the capacity to fix a
large quantity of N, which is used for its growth in late
winter and early spring. As warm, wet, summer
weather encroaches, white clover plants usually de
teriorate and finally die. With death, the stolons and
roots which have very high N concentrations are de
graded by other soil microorganisms, and N is min
eralized (converted into mineral forms) and used by
the accompanying warm-season grass.
The capacity of the white clover-Pensacola bahia
grass combination on the Spodosols to fix and utilize
atmospheric N is illustrated in Table 5. The legume-
grass combination produced as much forage as the
grass with 224 kg of N/ha/year, and some of this
forage was produced in February and March when
green forage was extremely scarce. Thus, the grazing
season was extended. The N content of the white
clover-grass forages was equal to that contained in
grass alone with a N rate of 448 kg/ha, and some of the
N protein is contained in the February-March clover
production. The quantities of the forage and protein
were equal to those produced by grass with an N ap
plication rate between 224 and 448 kg/ha/year, with
a potential savings of $125 to $250/ha/year. Since
almost no farmer or rancher uses this quantity of fer
tilizer N on pastures, it is readily apparent that pro
duction is not only more economical with the legume-
grass sward but that it is far higher than is normally
achieved from grass alone with fertilizer N.
To grow the legume, it is best not to over-drain the
Spodosols. In some areas of central Florida, irrigation
may be necessary for white clover because winter rains
are less reliable than in north Florida. The soil pH,
Ca, and Mg requirements for legumes are generally
higher than for grasses so more attention must be given
to liming. The requirements for P and K are also more
specific, particularly for seedling development, so care
must be exercised to apply the fertilizer at the proper
time. This should normally be in November. It should
be emphasized, however, that the P and K requirements
of the legume-grass combination under grazing are gen
erally no higher than for the grass alone at a high level
of productivity. Amounts of P and K that must be ap
plied with a grazing system are much less than the
amounts used annually by the plants; utilization ef
ficiencies higher than 100% are a consequence of
nutrient recycling through urine and feces deposited
TABLE 5.Forage production and nitrogen of white clover-
Pensacola BAHIAGRASS AND NITROGEN-FERTILIZED PENSACOLA BAHIA
GRASS ON A SPODOSOL.
N Oven-dry forage Forage N
Forage species applied
Mar. 15
Total
Mar. 15
Total
ks:/ha/year
White clover 4
P. bahiagrass
0
1,990
11,380
71
249
P. bahiagrass
0
0
3,100
0
34
P. bahiagrass
112
0
7,350
0
87
P. bahiagrass
224
0
11,840
0
165
P. bahiagrass
448
0
15,690
0
255
7
by the cattle. Beef (calf) production from white clover
and grass is illustrated by data from the Beef Research
Unit (Table 6). Forage production was approximately
maximum with only 36 kg of P and 67 kg of K/ha/
year. Weaning weights were higher than from grass
alone (Table 4).
The same quantities of P and K were applied to
the grass and to the legume-grass mixture. The grass
received 134 kg of N/ha/year but none was applied to
the legume-grass mixture. Beef production per cow was
substantially higher from the legume-grass than from
grass alone and beef production per ha was about 50 %
higher than from grass with the highest fertilization
rate. The savings by eliminating N fertilizer in this
case would be approximately $59/ha/year.
SUMMARY AND CONCLUSIONS
The production of forages and cattle on Floridas
mineral soils is a complex and relatively expensive
business. Price of inorganic nutrients as lime and fer
tilizer is a major, but by no means the only, produc
tion cost. Forages are produced seasonally and utilized
principally for grazing; therefore, it is frequently dif
ficult to place a value on them. If forage is harvested
for hay, a market value can be fixed and production
costs can be calculated. Thus, the data in Table 2
indicate that 11.2 metric tons of forage can be pro
duced with approximately $194 worth of lime and
fertilizer. Even with some spoilage, the current value
of hay would indicate that this is likely a profitable
operation.
In comparison, we have used fertilizer and beef
production levels from the Beef Research Unit (Roger
et ah, 1961) to compare grass with white clover-grass
(Table 7). Nutrient requirements of the two plant
systems were the same except for fertilizer N which
was applied to the grass; forage production was the
same. Because of better distribution of forage and
higher quality, beef production from the legume-grass
was 40% higher than that from the grass pastures.
Lime and fertilizer costs per kg of beef, at current
prices, are $0.51 for the grass and $0.18 for the legume-
grass pasture.
The perennial grasses are more hardy and more
drought resistant than the annual legumes. Also, dur
ing the growing season, grass production can be con
trolled by adjusting the nutrient supply, particularly
the N level. However, in spite of the excellent response
of grasses to fertilization, the value of the product
when grazed by cows and calves is frequently only
marginally profitable. Legumes require more careful
management and probably are not quite as reliable as
the grass. Even with some shortcomings, legumes must
TABLE 6.Production performance of cows on white clover-
grass PASTURES ON SPODOSOLS, BEEF RESEARCH UNIT.f
Fertilization
Annual
forage
production
Weaning
%
Beef production
N
P
K
Per ha
Per cow
kg/ha/year
kg/ha
kg -
0
36
36
9,810
85
315
171
0
72
72
10,150
82
314
156
fGrasses were Pensacola bahiagrass, Pangla digitgrass, and
Coastal bermudagrass.

8
Soil and Crop Science Society of Florida
TABLE 7.Nutrient costs and beef production from grass and
WHITE CLOVER-GRASS PASTURES ON A SPODOSOL AT THE BEEF RESEARCH
Unit.
Nutrients
Nutrients
Nutrients applied
Rate
Cost
Rate
Cost
kg/ha .fP/ha
Grass
kg/ha $/ha
White
clover-grass
N
134
59
0
0
P
30
30
36
30
K
30
17
36
17
Limef
7.4
7.4
Micronutrients+
2.5
2.5
Total
115.9
56.9
Forage production, kg/ha
9,630
9,810
Beef production, kg/ha
226
316
fData were taken from Koger et al. (1961).
:i:Lirne and micronutrients were prorated using 2.24 metric
tons of dolomitic lime and 28 kg of fritted micronutrients/ha
applied once per 4 to 5-year interval.
be included in the forage program if we are to con
tinue the trend toward intensified beef production.
Some fertilizer N will be needed for production of hay
or silage for winter feeding, but it cannot be the major
stimulus to forage production.
RECOMMENDATIONS
Soil pH should be maintained at approximately
6.0 by application of calcitic and dolomitic lime to
maintain the proper balance of Ca and Mg. Soil tests
through the County Agricultural Extension Agent
should be used as needed. Micronutrients should also
be applied if not previously used. A micronutrient frit
can be used, or alternatively, salts of Mn, Cu, Zn, Fe,
Mo, and B. Directions for their use should be followed
closely to avoid toxicities. For maintenance of a
sustained production system, N, P, and K should be
applied in a 4:0.4:1.7 ratio (4:1:2, N:P205:K20 ratio)
for grasses and a 0:0.4:1.7 ratio (0:1:2, N:P205:K20
ratio) for legume-grass mixtures. Nitrogen can be ap
plied at rates as high as 448 kg/ha/year for grasses for
intensive hay production; normally the rate will be
lower, particularly for grazing. A fertilizer with P and
K in a 0:4:16 ratio at 448 kg/ha/year (0:10:20 at
448 kg) is satisfactory for legume-grass mixtures. This
should be applied in the fall for white clover and in
the spring for summer legumes; a second application
may be made in the spring for white clover. Nitrogen
is not recommended for the legumes if the soil is prop
erly limed and fertilized, and the legumes are inocu
lated. Sulfur should be included annually. A higher
proportion of P may be needed initially, particularly
on soils of west Florida where P fixation may be
relatively severe.
LITERATURE CITED
Barber, S. A., and R. A. Olson. 1968. Fertilizer use on corn,
p. 163-188. In L. B. Nelson (ed.) Changing patterns in fer
tilizer use. Soil Sci. Soc. Am., Madison, Wis.
Blue, W. G. 1971. Nitrogen fertilization in relation to seasonal
Pensacola bahiagrass forage nitrogen and production on
Leon fine sand. Soil and Crop Sci. Soc. Florida Proc. 31:75-77.
Koger, M., W. G. Blue, G. B. Killinger, R. E. L. Greene, H. C.
Harris, J. M. Myers, A. C. Warnick, and N. Gammon, Jr.
1961. Beef production, soil and forage analyses, and economic
returns from eight pasture programs in North Central Florida.
Fla. Agr. Exp. Sta. Tech. Bull. 631.
Koger, M., W. G. Blue, G. B. Killinger, R. E. L. Greene, J. M.
Myers, N. Gammon, Jr., A. C. Warnick, and J. R. Crockett.
1970. Production response and economic returns from five
pasture programs in North Central Florida. Fla. Agr. Exp.
Sta. Tech. Bull. 740.
Koger, M., R. E. L. Greene, G. B. Killinger, W. G. Blue, and
J. M. Myers. 1977. Pasture programs and beef cattle breeding
systems for beef production in North Central Florida. Fla.
Agr. Exp. Sta. Tech. Bull. 789.
Smith, R. L., C. E. Hutton, and W. K. Robertson. 1968. The
effect of nitrogen on the yield of soybeans. Soil and Crop Sci.
Soc. Florida Proc. 28:18-23.
Integrating Native Range and Pasture
E. R. Felton1
This paper outlines the range-management pro
gram currently being followed by ALICO, Inc., a
publicly owned corporation. ALICO stock is traded
over-the-counter. The Company consists of lands for
merly owned as a subsidiary of the Atlantic Coastline
Railroad Company.
Initial development of the land followed guidelines
established by making a comprehensive study of land
types and capabilities. The objective was to develop an
operation that would best utilize this acreage for
sustained agricultural production. There evolved a pro
gram of cattle, citrus, and timber production which are
the main businesses of ALICO, Inc.
In this report, concentration will be on the cattle
operation which includes a range cow/calf operation
in southern Florida combining native and improved
iVice-President, Citrus and Cattle, ALICO, Inc., LaBelle,
Florida 33935.
pastures, and a backgrounding and finishing operation
in southern Georgia. The range cattle operation is
located in Hendry County southeast of LaBelle in
whats known as the Devils Garden area. This area is
typical of the pine, palmetto, and semiprairie country
of central and southern Florida.
Like many ranchers, we went into the cattle busi
ness with native cows crossed with purebred Brahman
bulls. The Brahman cross cows are then bred back to
English bulls (Hereford and Angus). We then follow
a criss-cross breeding system where English bulls are
bred to cows with predominately Brahman character
istics, and Brahman bulls are bred to cows with pre
dominately English characteristics. This produces an
animal with a high degree of hybrid vigor that is well
adapted to south Florida range conditions, and has the
desirable beef type and fleshing ability to respond well
to the backgrounding and finishing operation. The
best quality heifers are kept for herd replacement, and

Proceedings, Volume 39, 1980
the remainder of the heifer and steer calves are shipped
to our Georgia feedlot. These calves are weaned and
shipped at 6 to 8 months of age, heifer calves averaging
160 kg (350 pounds) and steers 204 kg (450 pounds).
Our pasture program is based on a system that com
bines native range and improved pastures in rotational
grazing; a ratio of 0.4 ha (1 acre) improved pasture
and 2 ha (5 acres) native range is used per cow/calf
unit per year. For example, improved pastures are fer
tilized in the spring and early summer, and as growth
starts, the cows with calves are placed on the improved
pastures where they remain until fall when the calves
are weaned. Following weaning, the cows are placed on
native pastures which have been lightly stocked (with
dry cows) or vacated during the summer growing
season. This results in a large amount of roughage ac
cumulated for grazing during the fall, winter, and into
the next spring.
When cows and calves are moved into the improved
pastures in the spring, the calves are branded, marked,
vaccinated, dehorned, and castrated; dry cows are sep
arated and put back on the native range. This has
proven to lie a good economic practice since forage
from fertilized pastures is utilized only by the cow and
calf. Since nutrient requirements of dry cows are con
siderably less than those for cows with calves, we are
able to maintain cows in good condition on the native
range.
The main factor that determines when cows are
rotated from one type pasture to another is weather.
If we have an early spring with good moisture, we
fertilize early and move the cows with calves into the
improved pastures in February or March. During
springs that are subjected to long dry spells, the cows
and calves are not moved until May and early June.
Over a period of years, a cow will average spending 6
months on improved pasture and 6 months on native
range. Flowever, with every period of severe weather,
whether it be flood, drouth or cold, we find ourselves
depending more on the native range. For example, the
severe winters of 1957 and 1962 produced unseasonable
amounts of rain with unusual cold; as a consequence,
there was virtually no production of forage on the im-
9
proved pastures. Flowever, due to reserve roughage in
the native pastures, we were able to maintain our cattle
in satisfactory condition. Even in normal winters the
cool, dry weather causes our Pensacola bahiagrass
(Paspalum notatum Flugge) and Pangla cligitgrass
(Digitaria decumbens Stent.) to become more or less
dormant and they become our poorest pastures. This is
the period when we depend most heavily on the
roughage provided by the native range. Another reason
that we consider the native range to be the backbone of
our cattle business.
Another critical situation that is helped considera
bly by the native-improved pasture system is the strain
of a low cattle market. The economics of our rotational
system are far better than we would realize from a
system of all improved pastures, or one consisting en
tirely of native range.
Our range improvement practices have been very
encouraging in that we have experienced a tremendous
increase in forage production. We chop palmetto-
prairie type range with a Marden chopper during the
winter and early spring, rest during the spring-summer
growing season to permit range plant establishment
and growth, and begin grazing in the fall. This practice
controls undesirable species and increases growth of
better forage plants. It has boosted the yield of range
forage from 1,800 kg/ha (1,600 lbs/acre) to 6,700
kg/ha (6,000 lbs/acre) as measured by the Range Con
servationist of the Soil Conservation Service. The
initial chopping will cost about $52/ha ($21/acre) and
is repeated about every 3 years so that the overall cost
is $17.30/ha ($7/acre/yr). Even with no fertilizer, we
have ranges of well-managed creeping bluestem grass
that are equal in yield to our conservatively fertilized
improved pastures.
Control burning every other year helps maintain
the stand and improves quality of forage on the native
range. These ranges are supplemented with a free
choice mixture of minerals, proteins, and vitamins.
The combination of native range and improved
pasture in the right ratio to provide the proper stock
ing rate has proven to be an economical and efficient
management system.
Properties of Representative Peninsular Florida Soils
Used for Range and Pasture1
Victor W. Carlisle2
ABSTRACT
Physical, chemical, and mineralogical properties of
six soils representative of the six extensively occurring
soil Orders in Peninsular Florida were determined to
provide a better understanding of the behavior of these
soils when used for range and pasture forage produc-
iFlorida Agricultural Experiment Stations Journal Series No.
2264. This research was partially supported by State Legislative
appropriations (administered by the Department of Agriculture
and Consumer Services) and supplemental funds contributed by
participating counties in support of the Florida Cooperative Soil
Survey.
2Professor of Soil Science, Soil Science Department, University
of Florida, Gainesville, FL 32611.
lion. Particle size distribution of all mineral soils was
dominated by quartz sand. Water retention values were
greater in horizons containing enhanced amounts of
organic C and in argillic horizons. Extractable Ca and
Mg were low in all mineral soils and high in the or
ganic soil. Extractable Na and K were low in all soils.
Cation exchange capacity was generally highest in sur
face horizons which usually contained largest amounts
of organic C but CEC also increased in the argillic and
spodic horizons. Surface soil pH was acid in all soils.
Varying amounts of montmorillonite, 14 intergrades,
kaolinite, gibbsite, and quartz were identified from
X-ray diffraction patterns.
Additional Index Words: Soil characterization, Al-
fisol, Entisol, Histosol, Inceptisol, Spodosol, Ultisol.

10
Soil and Crop Science Society of Florida
Most improved pasture in Florida is grazed in com
bination with large areas of native range. Ranches are
large, the most common size being about 1,600 ha
(Carter, 1978). Fourteen hundred of the larger ranches
in Peninsular Florida are operating on approximately
4,200,000 ha. Some animals are kept on improved pas
ture continuously, but most of them have access to
native range during at least part of the year.
Roger et al. (1961) in a comprehensive study of
pasture programs reported highest net returns from
grass-clover pastures that were not irrigated. Similar
results were reported by Peacock et al. (1975) compar
ing native range, native range plus improved grasses,
and improved grass-clover pastures. Regardless of the
production systems used, soil characteristics and man
agement practices largely determine the relative eco
nomic merit of various forage species.
The objective of this research was to compile soil
characterization data that would provide a better un
derstanding of the behavior of representative Peninsu
lar Florida soils when used for range and pasture
forage production.
MATERIALS AND METHODS
Six soils representing six commonly occurring soil
Orders were sampled from freshly exposed pits at dif
ferent geographical locations in Peninsular Florida
(Fig. 1). All horizons were described and sampled for
characterization by the Florida Soil Characterization
Laboratory at Gainesville; however, only laboratory
results for the major horizons of each pedon are pre
sented in this study. In addition to bulk samples, un
disturbed 5.4 x 3.0 cm cores were collected from most
horizons for bulk density, water retaining, and water
transmitting properties.
Samples were air-dried, passed through a 2-mm
aluminum sieve, and thoroughly mixed before pro
ceeding with particle size distribution, chemical, and
mineralogical analyses. Particle size distribution was
determined by the hydrometer procedure of Bouyoucos
(1962) modified by determining actual weights of sand
fractions. Soil cores were placed in Tempe pressure
cells, saturated, and then extracted at sequential pres
sures to determine water retained at 1/10 and 1/3 bars.
Before drying, the cores were resaturated for determi
nation of saturated hydraulic conductivity. After oven
drying the samples were ground to pass a 2-mm sieve
and the 15-bar water retention was determined.
Extractable bases were replaced by leaching 25 g
of soil with 250 ml of LOA NH,OAc buffered at pH
7.0. Calcium and Mg were determined by atomic ab
sorption; K and Na by flame emission. Extractable
acidity was determined by the BaCL-triethanolamine
(pH 8.2) method. Cation exchange capacity (CEC) was
calculated from the sum of extractable cations and
acidity. Organic C was determined by acid dichromate
digestion and soil reaction (pH) by glass electrode in
1:1 soil-liquid ratios of water and LOA KC1.
Clay was separated from sand and silt by wet siev
ing, centrifugation, and decantation. X-ray diffraction
patterns were obtained with a General Electric XRD-7
instrument using graphite-filtered CuKa radiation.
Samples were prepared for analysis by orienting ap
proximately 225 mg of clay on unglazed ceramic tile
(Rich, 1969). X-ray diffractograms were obtained from
Mg-saturated glycerol-solvated samples with no heat
treatment, K-saturated samples with no heat treatment,
and K-saturated samples after heating to 550 C for 4
hours. Relative amounts of clay minerals were esti
mated from the X-ray diffractograms.
RESULTS AND DISCUSSION
Soils selected for this study are commonly used for
range and pasture in Peninsular Florida. They belong
to the excessively, well, poorly, and very poorly soil
drainage classes (Table 1). As indicated by the family
classification, all of these soils occur in the hyper
thermic temperature zone and none contain appreci
able weatherable minerals. The Candler soil is un
coated (less than 5% silt plus clay in the control
section) and the Pahokee is an organic soil with high
base saturation (euic). Argillic horizons are present
only in the Arredondo and Felda soils.
The sandy nature of the mineral soils investigated
is indicated in Table 2. With exception of the organic
soil (Pahokee), sand was by far the major fraction in
all pedons. Surface horizons of all soils, except Pahokee,
contained more than 89% sand. Candler, Myakka, and
Placid soils contained in excess of 92% sands in sub
soils to depths of 2 m. Silt contents of these soils ranged
from 0.5 to 3.9%. Argillic horizons in the Arredondo
and Felda subsoils contained a preponderance of sands,
low silt content similar to the other mineral soils, and
an enhancement of clay ranging from 8.5 to 36.7%.
Distribution of sand fractions in the upper horizons of
the mineral soils indicated considerable homogeneity
of parent materials in these soils. Particle size distribu
tion was not attempted on the Pahokee soil.
Hydraulic conductivities (Table 2) of the sandy
horizons in these soils were quite high, frequently in
excess of 15 cm/hr. Predictably, the highest hydraulic
conductivity values were recorded for the excessively
drained Candler soil and the lowest values for argillic
horizons occurring at considerable depth in the Ar
redondo and Felda soils. Although hydraulic conduc
tivity was lower in the spodic horizon than other hori
zons determined for the Myakka soil, it was consider
ably higher than values commonly recorded for
Fig. 1 .Location of sample sites.

Proceedings, Volume 39, 1980
11
TABLE 1.Classification and natural drainage of selected soils.
Classification Natural
Soil Order Subgroup Family Drainage
Arredondo
Ultisol
Grossarenic Paleudult
Loamy, siliceous, hyperthermic
Well
Candler
Entisol
Typic Quartzipsamment
Uncoated, hyperthermic
Excessively
Felda
Alfisol
Arenic Ochraqualf
Loamy, siliceous, hyperthermic
Poorly
Myakka
Spodosol
Aerie Flaplaquod
Sandy, siliceous, hyperthermic
Poorly
Pahokee
Histosol
Lithic Medisaprist
Euic, hyperthermic
Very Poorly
Placid
Inceptisol
Typic Humaquept
Sandy, siliceous, hyperthermic
Very Poorly
TABLE 2.Physical properties of selected soil horizons.
Bulk
Particle size distribution
Hydr.
cond.
density
field
1/10
Water content
1/3
15
Soil
Depth
Horizon
Sand
Silt
Clay
(sat.)
moist
bar
bar
bar
cm
% of <2
mm
cm/hr
g/cc
% (wt) ......
Arredondo
0-20
Ap
90.7
5.6
3.7
14.9
1.49
10.0
6.5
2.5
104-137
A23
97.4
0.8
1.8
26.1
1.54
3.7
1.8
0.7
157-175
B21t
86.7
0.0
13.3
1.0
1.67
16.5
12.7
6.4
175-203
B22t
62.4
0.9
36.7
0.1
1.58
24.5
22.1
12.2
Candler
0-8
A1
95.9
2.7
1.4
_
_
43-89
A23
96.9
1.2
1.9
77.6
1.50
2.7
1.7
0.7
89-203
A24
97.4
0.8
1.8
78.2
1.45
3.0
2.1
0.8
Felda
0-10
Ap
98.3
0.8
0.9
17.1
1.52
9.3
6.7
2.6
53-79
A23
96.8
2.4
0.8
13.2
1.60
6.3
2.5
0.9
79-112
B2H
84.4
4.6
11.0
0.1
1.68
19.6
17.3
7.7
147-203
B23tg
87.4
4.1
8.5

-
-
-
-
Myakka
0-8
A1
98.1
1.2
0.7
57.8
1.31
9.4
6.9
4.1
15-66
A22
99.0
0.5
0.5
30.9
1.44
4.8
3.1
1.9
66-76
B21h
92.2
4.7
3.1
26.5
1.44
20.2
13.3
2.7
160-203
B3&Bh
98.1
0.9
1.0

-
-
-
-
Pahokee
0-25
Oap


_
13.8
0.38
255.0
161.0
25-71
Oa2



40.5
0.13

440.0
277.4
71-107
Oa3


35.8
0.13
-
390.0
252.0
Placid
0-36
All
89.5
6.6
3.9
7.0
1.28
30.0
22.6
5.9
61-91
Cl
98.1
1.4
0.5
15.8
1.49
11.6
6.1
1.7
127-203
C3
98.6
0.9
0.5
23.6
1.56
4.3
2.8
1.4
Myakka soils in many other Florida locations (Cal
houn et ah, 1974; Carlisle et ah, 1978). In somewhat
poorly and poorly drained soils, horizons with low
hydraulic conductivity may perch a temporary water-
table for several days or weeks. If this perched water-
table is within reach of active plant roots, plants may
seasonally utilize far more water from the soil than
would be predicted from soil water retention data
alone. Differences in bulk density values were not
great in the mineral soils with slightly lower values in
surface horizons due to less compaction and higher
amounts of organic matter. Bulk density values for all
sapric horizons in the Pahokee soil were extremely low
due to the high content of organic matter in this
Histosol.
Water contents at 1/10, 1/3, and 15 bars (Table 2)
show lowest water retention in the excessively drained
Candler soil and highest amounts in the very poorly
drained organic soil (Pahokee). Retention of water is
somewhat greater in the surface horizons of the mineral
soils due to enhanced contents of organic matter. Ar
redondo and Felda soils have subsurface horizons with
greater amounts of clay. Retention of water in these
horizons is influenced by the clay content and retention
of larger amounts of water in the spodic horizon of the
Myakka soil is influenced by slightly higher clay con
tent and much higher organic matter content.
Generally, low values for extractable bases in the
Arredondo, Candler, Felda, Myakka, and Placid soils
(Table 3) are indicative of low inherent soil fertility.
Calcium and Mg were the predominant cations with
largest amounts occurring in the surface soils and
argillic horizons. Sodium was uniformly low and the
trace amounts of K further support the absence of
appreciable quantities of weatherable minerals in
these soils. Cation exchange capacity in these soils is
usually less than 10 meq/100 g. Lower CEC values oc
curred in the sandier horizons containing negligible
amounts of organic C. Small amounts of liming ma
terials applied to surface soils with low CEC will sig
nificantly alter soil reaction in the upper horizons. As
expected, extractable Ca and Mg were very high in the
Pahokee soil resulting in CEC values more than 10
times those recorded for the mineral soils. Also ex
pectedly, organic C contents were highest in the
Pahokee soil. Mineral soils contained highest organic
C contents in surface horizons, decreasing rapidly with
depth in all but the Myakka soil in which organic C
increased abruptly in the spodic horizon. Organic C
contents may be increased: by good management prac-

12
Soil and Crop Science Society of Florida
TABLE 3.Chemical properties of selected soil horizons.
Soil
Depth
Horizon
Ca
Extractable bases
Mg Na K
Sum
Extract.
acidity
CEC
Base
sat.
Organic
carbon
pH
H,0 KC1
(1:1) 1.0N
(1:1)
cm
meq/100g
%
%
Arredondo
0-20
Ap
2.8
1.0
tr
tr
3.8
5.8
9.6
40
1.43
5.4
4.8
104-137
A23
0.1
tr
0.0
tr
0.1
0.2
0.3
33
0.20
6.1
5.5
157-175
B21t
0.9
0.2
tr
tr
1.1
2.1
3.2
34
0.07
5.8
4.8
175-203
B22t
0.3
1.1
tr
tr
1.4
8.9
10.3
14
0.14
5.0
3.8
Candler
0-8
A1
1.3
0.2
tr
0.1
1.6
1.6
3.2
48
0.46
5.4
4.8
43-89
A23
0.1
tr
tr
0.1
0.2
1.0
1.2
16
0.02
5.7
4.6
89-203
A24
0.1
tr
tr
0.1
0.2
1.2
1.4
12
0.02
5.5
4.6
Felda
0-10
Ap
0.3
0.1
tr
tr
0.4
4.4
4.8
9
1.56
4.8
3.8
53-79
A23
0.3
0.1
tr
tr
0.4
0.2
0.6
61
0.04
6.1
5.5
79-112
B211
3.1
3.1
0.3
tr
6.5
2.9
9.4
69
0.11
6.9
6.2
147-203
B23tg
5.8
1.7
0.2
tr
7.7
1.7
9.4
. 82
0.07
6.5
5.9
Myakka
0-8
A1
0.3
0.2
0.1
tr
0.6
4.6
5.2
11
1.39
4.3
3.3
15-66
A22
tr
tr
tr
tr

0.8
0.8
7
0.12
5.6
4.1
66-76
B21h
0.1
0.1
0.1
tr
0.3
13.9
14.2
3
2.27
4.4
3.5
160-203
B3&Bh
tr
tr
tr
tr

6.6
6.6
1
0.71
5.1
4.5
Pahokee
0-25
Oap
107.8
24.8
2.6
0.6
135.8
0.8
136.6
99
37.60
6.1
5.6
25-71
Oa2
72.4
17.8
2.7
0.9
93.8
7.7
101.5
92
38.60
6.5
6.0
71-107
Oa3
54.6
17.3
2.9
1.0
75.8
8.7
84.5
90
37.60
6.2
5.8
Placid
0-36
All
0.5
0.2
0.1
tr
0.8
9.2
10.0
8
1.92
4.4
3.3
61-91
Cl
tr
tr
tr
tr




0.12
5.9
4.4
127-203
C3
tr
tr
tr
tr




0.06
6.3
4.8
tices. Blue (1979) reported changes from approxi
mately 1.1 to 2.5% organic C in the surface soil of a
Myakka fine sand during 25 years of continuous grass-
clover pasture.
Soil reaction (FLO) ranged from pH 4.3 to pH 6.9,
seldom varying more than 1.5 pH units between hori
zons of the same profile. The pH values in l.(W KC1
were between 0.4 and 1.5 pH units lower than the
water measurements.
Sand fraction (>50pm) mineralogy is siliceous in
the Arredondo, Candler, Felda, Myakka, and Placid
soils with quartz dominant in all pedons. Very small
amounts of ilmenite and other heavy minerals (not
reported) occurred in most horizons with the greatest
concentration in the very fine sand fraction. Mineral
ogy of the crystalline components of the clay fraction
(Table 4) indicated that this fraction was dominated
by a variety of clay minerals in the soil Orders occur
ring extensively throughout Peninsular Florida.
Kaolinite was the dominant mineral (Table 4) in
the Arredondo soil; 14 intergrades in the Candler;
montmorillonite in the Felda; and quartz in the
Myakka and Placid soils. Similar results were pub
lished for Aerie Haplaquods (Zelazny and Carlisle,
1971), Typic Quartzipsamments (Carlisle and Zelazny,
1975), and Grossarenic Paleuclults (Carlisle, 1976) in
TABLE 4.Clay mineralogy of selected soil horizons.
Soil
Depth
Horizon
Mont
morillonite
14
Intergrade
Kaolinite
Gibbsite
Quartz
Amorphous
cm
%, X-ray peak intensity
Arredondo
0-20
Ap
33
56
11
104-137
A23

41
41

18
157-175
B21t
6
29
60

5
175-203
B22t
17
18
54
-
11
Candler
0-8
A1
34
34
6
26
43-89
A23

36
22
15
27
89-203
A24
-
32
24
14
30
Felda
0-10
Ap
38
62
79-112
B21t
97


_
3
147-203
B23tg
97

1

2
Myakka
0-8
A1



100
66-76
B21h
31



69
160-203
B3&Bh
-
-
-
-

100
Placid
0-36
All
100
61-90
Cl
7
27
28

38
127 203
C3

20
16

64

Proceedings, Volume 39, 1980
other Peninsular Florida locations. Primarily due to
the relatively low amounts of clay occurring in the
surface horizons, clay mineralogy of Florida soils com
monly influences their suitability for range and pasture
less frequently than the total clay content.
According to Henderson (1952), soil characteristics
that should be considered for range and pasture pro
grams in Florida are: (a) texture, (b) organic matter
content, (c) reaction of surface horizon, (d) depth to
clay, (e) natural drainage or depth to watertable, and
(f) slope. These important properties influence soil
moisture and plant nutrient relationships; therefore,
the nature of the soil largely determines which species
should be grown and the management practices which
must be used for maximum forage production.
Data presented for Peninsular Florida soils show
close agreement with Soil Conservation Service native
rangeland plant production ratings: Pahokee > Placid
> Felcla > Myakka > Arredondo > Candler (personal
communication with Mr. C. W. Carter, Range Con
servationist, U.S. Department of Agriculture, Soil Con
servation Service, Gainesville, FL 32601). Similar re
sults may be expected for improved pastures; however,
productivity is usually modified by such practices as
water control, liming, and fertilization.
LITERATURE CITED
Blue, W. G. 1979. Forage production and N contents, and soil
changes during 25 years of continuous white clover-Pensacola
bahiagrass growth on a Florida Spodosol. Agron. J. 71:795-798.
13
Bouyoucos, G. J. 1962. Hydrometer method improved for making
particle analyses of soils. Agron. J. 54:464-465.
Calhoun, F. G., V. W. Carlisle, R. E. Caldwell, L. W. Zelazny,
L. C. Hammond, and H. L. Breland. 1974. Characterization
data for selected Florida soils. Soil Science Department Re
search Report No. 741.
Carlisle, V. W. 1976. Mineralogy of selected Florida Grossarenic
Paleudults and Ultic Hapludalfs. Soil and Crop Sci. Soc. Flor
ida Proc. 36:126-129.
Carlisle, V. W R. E. Caldwell, F. Sodek, III, L. C. Hammond,
F. G. Calhoun, M. A. Granger, and H. L. Breland. 1978.
Characterization data for selected Florida soils. Soil Science
Department Research Report No. 78-1.
Carlisle, V. W., and L. W. Zelazny. 1975. Pedon mineralogy of
representative Florida Typic Quartzipsamments. Soil and
Crop Sci. Soc. Florida Proc. 34:4347.
Carter, C. W. 1978. Ranching in the sunshine. Rangemans J. 5:
82-83.
Henderson, J. R. 1952. Florida pastures from the extension view
point. Soil and Crop Sci. Soc. Florida Proc. 12:105.
Roger, M W. G. Blue, G. B. Killinger, R. E. L. Greene, H. C.
Harris, J. M. Myers, A. C. Warnick, and N. Gammon, Jr. 1961.
Beef production, soil and forage analyses, and economic re
turns from eight pasture programs in north central Florida.
Florida Ag. Exp. Sta. Bull. 631.
Peacock, F. M R. E. L. Greene, E. M. Hodges, W. G. Kirk, and
M. Roger. 1975. Forage systems as related to the economics
of beef production in south central Florida. Soil and Crop
Sci. Soc. Florida Proc. 34:148-151.
Rich, C. I. 1969. Suction apparatus for mounting clay specimens
on ceramic tile for X-ray diffraction. Soil Sci. Soc. Amer. Proc.
33:815-816.
Zelazny, L. W and V. W. Carlisle. 1971. Mineralogy of Florida
Aerie Haplaquods. Soil and Crop Sci. Soc. Florida Proc. 31:
161-165.

14
Soil and Crop Science Society of Florida
SOILS SECTION
Fruit Yield of Florida Belle Strawberries as Affected by
Rates of a Resin Coated Fertilizer1
E. E. Albregts and C. M. Howard2
ABSTRACT
A resin-coated slow-release fertilizer called Osmocote
is used extensively in strawberry (Fragaria x ananassa,
Duch.) fruit production to reduce fertilizer leaching,
but only limited data are available as to the effect of
Osmocote rate on fruit yield with sandy soils. Rates of
700, 1050, and 1400 kg/ha of a 16-2.2-13.3 Osmocote
were evaluated during two seasons with overhead
sprinkler irrigation and during one season with drip
irrigation. Several fertilizer placements were used. Soil
tests taken prior to fertilizer application indicated high
levels of P and K in the soil. The soil organic matter
content was rated as low. Total yield, fruit weight,
plant size, and foliage color were not different because
of Osmocote rates or placements with either overhead
sprinkler or drip irrigation. Soil soluble salts were
above yield limiting levels and tended to increase with
increasing rates of Osmocote.
Additional Index Words: Slow-release fertilizer,
Scranton fine sand, Fertilizer placement.
Most strawberry (Fragaria x ananassa, Duch.) grow
ers include a slow-release N fertilizer as part of their
total N application. However, many growers use a fer
tilizer derived solely from a resin-coated slow-release
source named Osmocote.3 These growers wish to
eliminate the leaching that can occur with the inor
ganic fertilizer sources and overhead sprinkler irriga
tion (3, 4, 6, 9). Osmocote fertilizer will maintain a
higher soluble salts, NO,, and NH, concentration in
the root zone than will inorganic fertilizer (4). The
additional cost of Osmocote is justified by the as
surance that sufficient N and K will be available when
the plants need them (4). However, little research has
been done in Florida on the effect of Osmocote rates
on strawberry fruit yield. Osmocote is a resin-coated
fertilizer whose release rate is affected mostly by tem
perature (8). Since it is relatively expensive, growers
using Osmocote or any other fertilizer should apply no
more than is needed to grow the crop so as to control
production costs, energy inputs, and pollution. The
purpose of this study was to evaluate the effect of
Osmocote rates on fruit yields and soil soluble salts
with overhead and drip irrigation in a well drained
sandy soil.
MATERIALS AND METHODS
Experiments were conducted for three seasons
(1977 to 1979) on a well drained Scranton adjunct fine
sand (a siliceous, acid, thermic Typic Psammaquent)
iFlorida Agricultural Experiment Stations Journal Series No.
1968.
"Professors (Soil Chemistry and Plant Pathology, respec
tively), Agricultural Research Center, Dover, FL 33527.
3The use of trade names in this publication does not con
stitute an endorsement of the product.
at the Agricultural Research Center, Dover. Three
rates (700, 1050, and 1400 kg/ha) of Osmocote 16-2.2-
13.3, a formulation designed to become available in
the soil solution over a 7 to 8 month period, were ap
plied each season to black polyethylene mulched beds
fumigated with a mixture of methyl bromide and
chloropicrin. The fertilizer was banded in the bed
center about 3 cm below the soil surface the first
season. During the second season, fertilizer was ap
plied either (a) as in the previous season, (b) banded
10 cm deep under each plant row, or (c) banded 10 cm
deep and 5 cm inside plant rows. During the third
season, the fertilizer was banded 10 cm deep under
each plant row. A standard fertilizer practice (inor
ganic fertilizer) was not used in this study because
Osmocote, applied at the highest rate used in this
study, had been evaluated previously against the
standard practice and was shown to be a superior
product with respect to the retention of nutrients in
the root zone (3, 4). The area used for the experiment
during the third season was different from that used
the previous 2 years. During the first two seasons over
head sprinkler irrigation was used, and during the
third season drip irrigation was used. Sufficient irriga
tion was applied so as to keep beds moist. Florida
Belle strawberry plants were set each year during
October in double-row beds and irrigated with over
head sprinkler irrigation for establishment. Marketable
fruit were harvested, counted, and weighed twice
weekly from January through April. Soil samples were
taken at the end of the harvest season during the last
two seasons and at mid-harvest as well during the last
season. Five cores were taken across the plant bed in
two places in each plot to a depth of 15 cm with at
least one of each of the five cores coming from the fer
tilizer band. Care was taken during soil sampling and
extraction of the saturated soil solution so as to not
crush the Osmocote pellet. All cores from each plot
were then composited. Samples were analyzed for total
soluble salts and reported in mhos/cm x 103 electrical
conductivity at soil saturation. Soil samples were also
taken in the fall of 1976 and 1978 before fertilizer
application and extracted with the double acid ex
tracting solution (7). The 1976 soil test results indi
cated that the soil P and K were high (151 and 192
kg/ha P and K, respectively). The soil had a pH of
6.5, and the soil organic matter content was rated as
low. The 1978 soil test results also rated soil P and K
as high (151 and 142 kg/ha P and K, respectively).
The soil had a pH of 7.2, and the soil organic matter
content was rated as low. The saturated extracts from
these same soil samples had an electrical conductivity
of 0.20 and 0.10 mhos/cm at 25C for 1976 and 1978,
respectively. Plants were rated for color of foliage and
size at least twice per season. Plant size at each sam
pling date was rated on a scale of 1 to 10 with 10 being
the largest plant. Foliage color was rated on a scale of
1 to 4 with 1 being yellow and 4 being dark green.

15
Proceedings, Volume 39, 1980
RESULTS AND DISCUSSION
The foliage color was rated medium to dark green
during all seasons, and fertilizer treatments did not
affect foliage color except during March of the first
season (Table 1). Plant growth did not vary because
of treatment except during the first season, but growth
the first season was not improved with Osmocote rates
greater than 700 kg/ha. Reduction of the early plant
growth can be indicative of low soil fertility. January
fruit yields did not vary because of Osmocote rate or
placement except during the first season. April fruit
yields were not affected by Osmocote rate or place
ment during any season. An insufficient fertilizer rate
would more likely affect fruit yields late in the season
(April) with a long season crop such as strawberries.
Although total markeable fruit yields were less during
the second season, total marketable yields were not
different because of Osmocote rate or placement for
any season. Total marketable fruit yields were con
siderably greater than the average Florida yields (16.8
metric tons/ha) for the 1976-78 period (5). Average
marketable fruit weight was not different because of
treatment for any season. Fruit size may be reduced if
fertility is low (4).
The total soil soluble salts generally increased with
increasing rates of Osmocote, and the differences were
significant on two of the three sampling dates (Table
2). The total soil soluble salts in all treatments were
sufficient to produce high fruit yields (1, 2, 4).
The initial fertility of the soil used in these studies
with respect to K and P was high. The amounts of N,
K, and P applied to the soil by the lowest rate of
TABLE 2-Total soil soluble salt in top 15 cm of bed at vari
ous DATES.
Fertilizer
rate
April 1978
placementf
February
1979
April
1979
I
M
U
kg/ha
EC (mhos/cm x 103)f
700
1.91
2.15
2.10
4.37
1.88
1050
3.23
3.85
2.32
4.42
2.17
1400
3.33
5.63
2.10
10.67
2.62
§L##
L**
ns
L**
ns
fl = fertilizer banded 7 cm deep and 5 cm inside plant rows,
M = fertilizer banded in bed center 3 cm below surface, U = fer
tilizer banded under plant row.
^Conductivity of saturated soil extract.
§ Significance: L = linear, ** = 1% level.
Osmocote were If2, 93, and 15 kg/ha, respectively.
With respect to the fruit yields obtained in these
studies, the total uptake of N, K, and P would have
been less than 80, 80, and 12 kg/ha, respectively (2).
Therefore, with the soil supplying some of the N, K,
and P and with a slow-release fertilizer applied at rates
greater than plant uptake, the lower rates of Osmocote
used in these studies should have been sufficient to
produce the optimum yields obtained. The rate of
Osmocote to use on a particular soil will be dependent
on soil type, initial soil fertility, cultural system em
ployed, and cultivar grown. The application of rela
tively low rates of slow-release fertilizers to straw
berries makes their use more economically feasible.
TABLE LEffect of osmocote rate and placement on plant size, foliage color, marketable
FRUIT YIELD, AND AVERAGE FRUIT WEIGHT FOR THREE SEASONS.
Fertilizer
Yield (Mt/ha)
Seasonal avg.
fruit wt. (g)
Plant sizef
Foliage colonj:
January
April
Seasonal
December
March
December
March
Rate (kg/ha)
1976-77
700
2.3
2.5
27.9
16.7
9.2
9.8
3.8
3.0
1050
1.8
2.3
26.7
15.9
8.6
9.6
4.0
3.4
1400
4.2
4.0
27.8
16.7
9.2
9.8
4.0
3.2
§L*
ns
ns
ns
Q*
Q*
ns
Q*
Placement!! and
rate (kg/ha)
1977-78
I- 700
7.0
4.9
21.5
16.3
9.4
9.8
4.0
3.8
1050
7.2
6.3
23.7
14.8
9.6
9.4
4.0
3.2
1400
6.3
3.3
18.2
16.2
8.8
9.2
4.0
3.6
M- 700
5.8
5.9
22.7
15.6
8.6
9.4
3.8
3.4
1050
6.1
4.1
20.1
15.6
8.6
9.0
3.8
3.4
1400
5.9
5.1
20.2
16.2
8.6
9.0
3.8
3.2
U- 700
7.0
4.3
20.0
16.3
9.0
9.6
4.0
3.4
1050
6.5
4.4
20.0
15.3
8.8
9.8
4.0
3.2
1400
7.4
4.1
19.7
16.3
9.4
9.4
4.0
3.4
ns
ns
ns
ns
ns
ns
ns
ns
Rate (kg/ha)
1978-79#
700
4.2
17.6
28.3
14.6
9.3
9.7
4.0
4.0
1050
4.3
16.5
27.8
14.1
9.4
9.8
4.0
4.0
1400
4.0
15.8
26.7
14.7
9.2
9.6
4.0
4.0
ns
ns
ns
ns
ns
ns
ns
ns
fRelative plant size for date: Plant size rated on scale of 1 to 10 with largest plants rated as 10.
JColor rated on scale of 1 to 4 with 1 = yellow, 2 = light green, 3 = medium green, and 4 = dark green.
§Signilicance: L = linear, Q = quadratic. 5% level.
If I = fertilizer banded 7 cm deep and 5 cm inside plant rows, M = fertilizer banded in bed center 3 cm below surface, U = fertilizer
banded under plant row.
#Drip irrigation used in 1978-79; overhead sprinkler irrigation used in other years.

16
Soil and Crop Science Society of Florida
Lower rates of slow-release fertilizers are possible be-
case they maintain a higher soil nutrient level than
inorganic sources when applied at the same rate (4).
REFERENCES
1. Albregts, E. E., and C. M. Howard. 1973. Influence o£ fer
tilizer placement and rates on strawberry production and soil
fertility. Soil and Crop Sci. Soc. Fla. Proc. 32:89-92.
2. and 1977. Strawberry fertilization.
Dover ARC Research Report SV-1977-2.
3. and 1978. Influence of fertilizer sources
and drip irrigation on strawberries. Soil and Crop Sci. Soc.
Fla. Proc. 37:159-162.
4. and 1979. Effect of bed height and N
fertilizer sources on fruiting strawberries. Soil and Crop Sci.
Soc. Fla. Proc. 38:76-78.
5. Dozier, G. L. 1979. Marketing Louisiana Strawberries, 1979
crops. Louisiana State Market News Service.
6. Everett, P. H. 1978. Controlled release fertilizer: Effect of
rates and placement on plant stand, early growth, and fruit
yield of peppers. Fla. State Hort. Soc. Proc. 90:390-393.
7. Nelson, W. L., A. Mehlich, and E. Winters. 1953. The de
velopment, evaluation, and use of soil tests for phosphorus
availability. Agron. J. 4:153-188.
8. Patel, A. S., and G. C. Sharma. 1977. Nitrogen release char
acteristics of controlled-release fertilizer during a four month
soil incubation. J. Amer. Soc. Hart. Sci. 102:363-367.
9. Rhoads, F. M. 1977. Water and nutrient movement under a
surface moisture barrier in a sandy soil. Soil and Crop. Sci.
Soc. Fla. Proc. 36:68-71.
Copper Nutrition of Cucumber (Cucumis sativus L.)
as Influenced by Fertilizer Placement, Phosphorus Rate,
and Phosphorus Source1
A. A. Navarro and S. J. Locascio2
ABSTRACT
The effects of Cu rate, P rate and source, and fer
tilizer placement on cucumbers (Cucumis sativus L.)
were studied in field experiments on St. Johns fine sand
(sandy, siliceous, hyperthermic Typic Haplaquod). An
increase in Cu from 0 to 2.24 kg/ha increased total
yields from 11.2 to 21.4 ton/ha. A further increase in
Cu to 8.96 kg/ha increased yield to 24.7 ton/ha.
Cucumbers also responded significantly to P applica
tions. At P rates of 0, 28, 56, and 112 kg/ha, yields were
15.8, 21.2, 20.3, and 19.9 ton/ha, respectively. An inter
action between P and Cu rate on early yield was sig
nificant. Application of high Cu rates with low P rates
or high P rates with low Cu rates reduced yields. Yields
were highest with Cu applied at 8.96 and P at 56 kg/ha.
Fertilizer placement interacted with Cu rate on early
and total yields. An increase in Cu rate from 0 to 8.96
kg/ha increased yields 154% with the broadcast place
ment and 82% with the band placement. Total yields
were significantly greater with ordinary superphos
phate as the P source than with either diammonium
phosphate or concentrated superphosphate which were
comparable. Increased rates of P resulted in increased
P concentrations in plant tissues, but significantly re
duced tissue Cu 30 days after planting and at the har
vest stage. Increased rates of Cu increased tissue Cu at
both growth stages, but decreased P concentration at
the harvest stage.
Additional Index Words: Cu rate, Band placement,
Broadcast placement.
In Florida, early studies on Cu requirements of
vegetables were limited to organic soils (1). On mineral
soils, more recent studies have shown substantial re
sponses to Cu application for watermelons (7, 9).
J Florida Agricultural Experiment Stations Journal Series No.
2147.
^Formerly Graduate Assistant and Horticulturist, Vegetable
Crops Department, respectively, University of Florida, Gaines
ville, FL 32611.
Watermelon response to organic sources of N were
shown to be due primarily to Cu impurities in the
fertilizer (7). Watermelon requirement for Cu when
grown on a number of mineral soils was approximately
4.48 kg/ha. Phosphorus rate and source were found to
influence Cu uptake (5, 9). Increased rates of applied
P depressed Cu uptake by watermelons and reduced
yields unless Cu rates were also increased. Fertilizer
placement was also found to affect watermelon yield
(6, 10) and Cu uptake (11); its effect was most pro
nounced at high Cu levels. The purpose of this study
was to evaluate the effects of P rate, P source, and fer
tilizer placement on Cu requirements of cucumbers
(Cucumis sativus L.).
MATERIALS AND METHODS
Field Experiments: Two similar experiments were
conducted in 1971 and 1972 on two adjacent newly
cleared areas of St. Johns fine sand located near Gaines
ville. The soil pFI was 3.9 with 5.5% organic matter
content and 1 ppm Cu. Treatments were factorial com
binations of three P sources, diammonium phosphate
(DAP), ordinary superphosphate (OSP), and concen
trated superphosphate (CSP); four P rates, 0, 28, 56,
and 112 kg/ha; four Cu rates, 0, 2.24, 4.48, and 8.96
kg/ha; and two fertilizer placements, band and broad
cast.
Fertilizer treatments were formulated to include N
at 134 kg/ha (one-fourth in the nitrate form, and
three-fourths in the ammonium form), and 134 kg/ha
of K equally from KC1 and K2S04. Treatments were
arranged in a randomized block design with three
replications.
In 1971, the field was limed 1 week before planting
and in 1972 lime was applied 1 month before planting.
In both seasons, CaC03 was applied at 9,000 kg/ha
which raised the soil pH to 5.5. Fertilizer was applied
before planting on beds 1.2 m apart. With the band
placement, the fertilizer was applied in a single band
located 6.4 cm deep and 6.4 cm to the side of bed
center. For the broadcast placement, fertilizer was ap
plied in a 1-m strip on the bed surface and incorpo-

17
Proceedings, Volume 39, 1980
rated to a depth of 15 to 20 cm. Poinsett cucumber
seeds were planted in a single row in the bed center.
Seedlings were thinned to a final spacing of 61 cm. At
the last thinning (30 days after seeding), plants were
sideclressed with 34 kg/ha N as NH.,N03.
First fruits were harvested 55 days after planting
and harvests continued at 3 to 4-clay intervals for eight
harvests in 1971 and five in 1972. Whole plant samples
were collected for tissue analyses 30 days after planting
and recently mature leaves were sampled at harvest.
Plant tissues were oven-dried (70C) and ground with
a Wiley mill. Two-gram samples of the tissues were
dry-ashed at 500C. The ash was disolved in 50 ml of
IN HCL. A 25-rnl aliquot was evaporated to dryness on
a hot plate and volume brought back to 10 ml with IN
HC1. Copper and Fe were determined by atomic ab
sorption spectrometry and P was determined color-
imetrically by the phosphomolybdate method (8).
RESULTS
Effects of Cu rate. The main effects of Cu rate on
total yield of cucumbers for the two seasons are shown
in Table 1. Response to Cu varied during the two
seasons. With an increase in Cu rate, yields were in
creased over four times in 1971 and almost doubled
during 1972. Yields with the 0, 2.24, 4.48, and 8.96 kg
Cu/ha rates were 3.6, 10.6, 11.4, and 15.2 ton/ha in
1971 and 18.9, 32.1, 31.4, and 34.2 ton/ha in 1972, re
spectively. Application of Cu resulted in an increase
in tissue Cu concentration 30 days after seeding and at
harvest (Table 1). Iron concentration in plant tissue
at both sampling periods and P tissue concentrations
at harvest were depressed by increased Cu applications.
Copper deficiency symptoms were observed on
plants not fertilized with Cu and were aggravated by
increasing P rate. Copper-deficient young plants ex
hibited symptoms such as rolling and cupping of the
leaves and cessation of terminal growth. At a later
stage, marginal chlorosis developed on young and
mature leaves which progressed towards the base of the
leaves through the interveinal areas. The areas immedi
ately around the leaf vein remained green. At a more
advanced stage, the chlorotic areas became necrotic.
On mature plants, the initial symptom was marginal
leaf chlorosis followed by necrosis.
Effects of P rate. Phosphorus and Cu rates inter
acted in their effects on early yield and on tissue Cu
concentration (Table 2). High rates of Cu with low
rates of P reduced yield. Conversely, high rates of P
with low amounts of Cu also decreased yields. Highest
early yields were obtained with Cu at 8.96 kg/ha and
P at 56 to 112 kg/ha. The highest level of Cu in the
plant tissue was obtained at a Cu rate of 8.96 kg/ha
and with no added P. At all rates of Cu application, Cu
concentrations in the plant tissue were decreased with
TABLE 1.Main effects of copper rates, phosphorus rates, phosphorus sources, and fertilizer
PLACEMENT ON CUCUMBER YIELD AND MINERAL COMPOSITION OF PLANT TISSUES (MEAN OF 1971 AND 1972
SEASONS).
Time of sampling
Total
30 days after planting
At harvest
Treatment
Yield
Cu
P
Fe
Cu
P
Fe
Cu, kg/ha
ton/ha
ppm
%
ppm
ppm
%
ppm
0
11.23
6.0
0.74
138
2.7
0.47
105
2.24
21.37
7.0
0.75
132
3.2
0.42
90
4.48
21.40
7.6
0.75
136
3.2
0.42
81
8.96
24.72
9.4
0.74
134
3.6
0.41
82
F valuef
L**Q**C**
L**
N.S.
C**
L**
L**Q*
L**Q**
P,kg/ha
0
15.81
8.9
0.45
146
3.5
0.24
90
28
21.23
7.2
0.66
136
3.3
0.36
93
56
20.34
6.9
0.78
134
3.1
0.44
86
112
19.88
7.0
0.90
131
2.9
0.56
90
F valuef
C*Q**
L**Q**C**
L**Q**
L**
L**Q**
q*#C**
P source
OSP
21.86a
6.9b
0.79
135
3.3
0.44
91
DAP
19.20b
7.3a
0.76
133
3.2
0.46
91
CSP
19.90b
7.0b
0.79
132
2.8
0.45
86
F valuet
##
##
N.S.
N.S.
N.S
N.S.
N.S.
Placement
Band
16.22
6.7
0.75
139
3.0
0.43
91
Broadcast
23.51
7.8
0.74
131
3.3
0.43
88
F value§
Year
##
##
N.S.
##
##
N.S.
##
1971
11.80
8.4
0.75
129
3.57
0.41
86
1972
27.22
6.0
0.75
141
2.72
0.45
93
F value §
**
##
N.S.
#
N.S.
N.S.
#
fRate effects were linear (L), quadratic (Q), and cubic (C) at the 5% (*) and 1% (**) levels.
Difference between P sources was significant at the 5% (*) level and was separated by orthogonal comparisons or was not significant
(NS).
§Differences between placement and year were significant at the 5% and 1% levels or were not significant.

18
Soil and Crop Science Society of Florida
TABLE 2.Interaction of P and Cu rates on Cu content of
CUCUMBER PLANTS 30 DAYS AFTER SEEDING AND ON EARLY YIELD (1971
AND 1972 POOLED DATA).
P, kg/ha
Cu, kg/ha
0
2.24
4.48
8.96
Mean
Plant Cu, ppmf
0
7.14
8.12
8.24
12.12
8.91
28
5.04
7.07
7.44
9.34
7.22
56
5.44
6.74
7.63
7.74
6.89
112
6.54
6.04
7.12
8.31
7.00
Mean
6.04
6.99
7.61
9.38
Fruit Yield, ton/haf
0
2.79
5.57
7.25
4.22
4.96
28
3.43
10.29
9.15
9.65
8.13
56
4.50
9.70
9.95
10.40
8.64
112
4.08
7.31
8.86
11.93
8.05
Mean
3.70
8.22
8.81
9.05
fP rate effects were linear (L)**, quadratic (Q)**, and cubic
(C)*, and Cu rate effects were L** at the 1% (**) level. Inter
action between P x Cu ** was significant.
fP rate effects were L* and Q**, and Cu rate effects were
L**, Q**, C** at the 5% (*) or 1% (**) level. Interaction be
tween P x Cu** was significant.
an increase in P application. Lowest concentrations of
tissue Cu were obtained with 0 Cu and 28 and 56
kg/ha P.
The main effects of P rate on total yield are shown
in Table 1. Yields were increased significantly with an
increase in P from 0 to 28 kg/ha. With a futrher in
crease in P, yields were slightly reduced. During the
1972 season, effects of Cu and P interacted on total
yield (Table 3). With low rates of either Cu or P and
increased rates of the other element, total yields in
creased quaclratically. However, with high rates of
either element yields increased linearly with an in
crease in the other nutrient. Yields tended to follow
this ¡iattein in 1971, but the interaction was not sig
nificant.
Effect of P source. Application of P from different
sources resulted in significant differences in total yields
and in the Cu concentration in plant tissue 30 days
after seeding and at harvest (Table 1). Total yields
TABLE 3.Effects of P and Cu rates on total cucumber yield
DURING 1971 AND 1972.
Cu, kg/ha
P, kg/ha
0
2.24
4.48
8.96
Mean
1971 yield, ton/haf
0
.75
6.80
10.45
3.22
5.30
28
2.55
12.60
9.40
17.90
10.61
56
2.70
11.05
14.40
15.55
10.95
112
6i50
9.45
10.80
16.15
10.75
Mean
3.59
10.62
11.44
15.22
1972 yield, ton/haf
0
19.75
24.41
31.51
29.61
26.32
28
19.95
37.10
36.71
33.66
31.86
56
19.54
33.54
31.71
34.08
29.72
112
16.81
29.29
30.52
36.47
28.02
Mean
18.87
32.12
31.37
34.23
|P rate effects were linear (L)* and quadratic (Q)**. Cu rate
effects were L** and Q* at the 5% (*) and 1% (**) levels. P x
Cu interaction was not significant.
fP rate effects were cubic (C)**, Cu rate effects were L*#,
Q**, C**. Interaction between P x Cu was significant.
were higher with OSP than with either DAP or CSP.
Yields with the latter two sources were comparable.
There was an interaction between P rate and source in
the 1971 experiment (Table 4). With OSP as the source
of P, there was a linear increase in yield with an in
crease in P rate from 0 to 112 kg/ha. However, with
CSP or DAP, yields were decreased when P rate was
increased above 56 kg/ha. In 1972, yields for the three
sources were 29.5, 31.5, 28.7 ton/ha, respectively, and
were not significantly different.
Tissues concentrations of P and Fe 30 days after
seeding and at harvest were not affected by P sources,
but tissue Cu levels were affected. At 30 days after
seeding, plants grown with DAP contained a signif
icantly higher Cu content (7.3 ppm) than plants grown
with OSP and CSP (6.9 and 7.0 ppm, respectively). At
the harvest stage, differences due to P-source were not
significant.
Effect of fertilizer placement. Cucumber yields dur
ing the two seasons were 45% greater with broadcast
than band fertilizer placement (Table 1). An inter
action between Cu and fertilizer placement signif
icantly affected early and total yields and tissue Cu
concentration (Table 5). Fruit yields and tissue Cu
concentrations increased with an increase in Cu with
both fertilizer placements, but increases were greater
with the broadcast than band placement. Fertilizer
placement had no effect on tissue Cu or yield at the
0 Cu rate.
TABLE 4.Interaction of P source and P rate on total cucum
ber yield, 1971.
Phosphorus
sources
P, kg/ha
28
56
112
Mean
ton/ha
OSP
13.76
11.08
17.83
14.22
DAP
9.54
10.52
9.19
9.74
CSP
8.62
11.26
5.19
8.36
Mean
10.61
10.95
10.75
P rate effects were linear at the 1% level for OSP but not
significant for DAP and CSP.
TABLE 5.Effect of fertilizer placement and Cu rate on the
Cu content of cucumber plants and on early and total fruit
YIELD (1971 & 1972 POOLED DATA).f
Placement
Cu, kg/ha
Cu, kg/ha
0
2.24
4.48
8.96
0
2.24
4.48
8.96
Tissue Cu, ppm
30 days after planting At harvest
Band
5.94
6.58
6.63
7.58
2.64
3.04
3.02
3.16
Broadcast
5.71
6.97
8.33
10.08
2.65
3.36
3.31
3.95
N.S.
N.S.
*
N.S.
N.S.
N.S.
#
Fruit yield, ton/ha
Early
Total
Band
3.14
5.73
5.74
6.27
10.58
17.69
17.34
19.23
Broadcast
4.19
11.13
11.88
13.29
11.90
24.99
26.93
30.21
N.S.
*
#
*
N.S.
#
#
#
fDifferences between placement at a Cu level were not signif
icant (N.S.) or were significant at the 5% (*) level.

19
Proceedings, Volume 39, 1980
DISCUSSION
In both experiments, total encumber yields and Cu
concentrations in plant tissues 30 days after seeding
and at harvest significantly increased with Cu applica
tions. The response of cucumbers to Cu was related to
the low concentrations of native Cu in the soil (less
than 1 ppm Cu extractable with O.UV HC1) and to the
Cu requirements of the crops. Similar responses to Cu
were reported for watermelons (5, 7, II).
High rates of P application with low Cu were re
ported to decrease crop yields and reduce Cu in the
tissue (2, 3, 4). Dekock et al. (3) observed that in
creased application of P increased plant demands for
Cu and under conditions of limited Cu, such enhanced
plant demand could induce Cu deficiency symptoms
and reduce crop yield. In this study, the application of
Cu also enhanced plant demand for P. Thus, yield de
creased with high Cu and with low P rates.
Ordinary superphosphate was found to be a better
source of P for cucumbers compared to DAP or CSP.
Similar results were obtained by Locascio et al. (8) on
watermelons. As shown in Table 4, the superiority of
OSP became more apparent at high rates of P applica
tions. This response may be related to the amount of
other micro or macronutrients in OSP.
In this study, Cu was more efficiently absorbed by
plants when applied broadcast than band; similar re
sults have been reported (11, 12). Interactions between
Cu rate and fertilizer placement were also observed in
this study. In the case of P uptake, banding the fer
tilizers 6.4 cm to the side and 6.4 cm below the seeds
was just as efficient as applying the fertilizers broadcast.
Iron concentrations of the plant tissues were lower with
broadcast placement, not as a result of placement, but
probably clue to high Cu in the plant tissues (13).
Significant correlations were found between total
yields and P on Cu concentration in the plant tissues
30 days after planting and at fruiting time. As shown
in Table 2, adequate P supply and availability in the
soil for cucumbers was indicated by tissue P concen
tration of at least 0.66% (whole plant, dry weight
basis) at 30 days after planting and at least 0.36% (leaf
sample) during the fruiting stage. For Cu, adequate soil
supply was indicated by a tissue Cu level of at least
6.8 ppm (whole plant, dry weight basis) 30 days after
seeding and at least 3.2 ppm (leaf sample) during the
fruiting stage.
LITERATURE CITED
1. Allison, R. V., O. C. Bryan, and J. H. Hunter. 1927. The
stimulation of plant response on the raw peat soils of the
Florida Everglades through the use of copper sulfate and
other chemicals. Florida Agrie. Exp. Sta. Bull. 190.
2. Bingham, F. T., and J. P. Martin. 1956. Effects of soil
phosphorus on growth and minor element nutrition of citrus.
Soil Sci. Soc. Amer. Proc. 20:382-385.
3. Dekock, P. C., M. V. Cheshire, and A. Hall. 1971. Comparison
of the effect of phosphorus and nitrogen on copper-deficient
and -sufficient oats. J. Sci. Food and Agr. 22:437-440.
4. Everett, P. H., S. J. Locascio, and J. G. A. Fiskell. 1966.
Phosphorus and copper effects on growth and yield of water
melons. Proc. Florida State Hort. Soc. 79:155-159.
5. Fiskell, J. G. A., H. L. Breland, S. J. Locascio, and P. H.
Everett. 1967. Effects of phosphate sources on copper and
zinc movement from mixed fertilizers and band placement.
Soil and Crop Sci. Soc. Florida Proc. 27:35-49.
6. S. J. Locascio, and F. G. Martin. 1970. Patterns of
fertilization for watermelon: II. Influence on nutrient dis
tribution in soil and plant uptake. Proc. Florida State Hort.
Soc. 83:149-154.
7. Locascio, S. J., P. H. Everett, and J. G. Fiskell. 1964. Copper
as a factor in watermelon fertilization. Proc. Florida State
Hort. Soc. 77:190-194.
8. P. H. Everett, and J. G. A. Fiskell. 1968. Effects
of phosphorus sources and copper rates on watermelons.
Proc. Amer. Soc. Hort. Sci. 92:583-589.
9. and J. G. Fiskell. 1966. Copper requirements of
watermelons. Proc. Amer. Soc. Hort. Sci. 88:568-575.
10. J. G. Fiskell and H. W. Lundy. 1970. Pattern of
fertilization for watermelons: I. Influence on plant growth
and fruit yield. Proc. Florida State Hort. Soc. 83:144-148.
11. and F. G. Martin. 1972. Influence of
fertilizer placement and micronutrient rate on watermelon
composition and yield. J. Amer. Soc. Hort. Sci. 97:119-123.
12. Navarro, A. A., and S. J. Locascio. 1973. Cucumber response
to copper rate and fertilizer placement. Proc. Florida State
Hort. Soc. 86:193-195.
13. Spencer, W. F. 1966. Effect of copper on yield and uptake of
phosphorus and iron by citrus seedlings grown at various
phosphorus levels. Soil Sci. 102:296-299.
Nitrogen Losses from Urea, Ammonium Sulfate, and
Ammonium Nitrate Applications to a Slash Pine Plantation1
D. B. Boomsma and W. L. Pritchett2
ABSTRACT
Nitrogen transformations and NH3 and NaO losses
were examined following broadcast applications of
urea and (NH4),S04 at 100, 200, 300, and 400 kg N
ha 1 to a 23-year-old slash pine (Finns elliottii var.
elliottii Engelm.) plantation on Wauchula fine sand
(Ultic Haplaquod). A second experiment in the same
general area compared denitrification rates from urea,
(NH4),S04, and NH4N03, applied in solution to the
forest floor at 200 kg N ha-1.
iFlorida Agricultural Experiment Stations Journal Series No.
2260.
sGraduate Assistant and Professor of Forest Soils, respectively,
Soil Science Department, University of Florida, Gainesville, FL
32611.
Rates of NH3 volatilization from urea applied at
400 kg N ha-1 were initially high (>1 kg N ha-1 day-1).
Urea was substantially hydrolyzed within 1 week of
application, resulting in a 1 to 2 unit increase in pH
of soil extracts. Measurements of net accumulation of
NOf indicated little nitrification with either fertilizer
material. Water extracts from urea-fertilized soils had
low concentrations of cations, including NH.,+, com
pared with those from (NH4)2SO.,-treated soils.
If a N2:N20 ratio of 10:1 was assumed, denitrifica
tion losses from urea or (NH4)2S04 represented ap
proximately 1 % of the applied N. If a N2:N20 ratio of
100:1 was used, however, losses from NH4N03 during
100 days following fertilization represented 29% of the
applied N. Volatilization of N following urea or
ammoniacal-N applications does not appear to be a

20
Soil and Crop Science Society of Florida
major pathway of loss in these forest soils and, hence,
leaching is likely to be of greater importance under
most conditions.
Additional Index Words: Forest fertilization, Pine
ecosystems, Nutrient cycling, Denitrification, Cation
loss, Pinus elliottii.
Nitrogen is the nutrient element most frequently
deficient in forest ecosystems. Growth responses to N
and P fertilization in the Southeastern Coastal Plain
have led to operational forest fertilization within this
region. This has occurred in spite of the fact that the
efficiency of N fertilization is often low, due to volatile
losses of NH3 (Volk, 1970), leachinglosses (Sarigumba
et al., 1976; Mead, 1975), and immobilization of ap
plied N (Sarigumba and Fiskell, 1975). Little research
has been conducted on denitrification within forest
ecosystems, even though environmental conditions
often seem to favor this process.
Overrein (1969) and Ogner (1972) reported that
applications of urea to thick humus layers resulted in
microbiological immobilization of urea-N into com
plexes that resisted subsequent mild extraction. The
extent of immobilization of added N appeared to be
in the order urea > NH,C1 > KN03 (Overrein, 1969).
In a review paper, Knowles (1975) suggested that the
additions of 100 ppm of NH.p-N or NO:f-N to the
forest floor may result in large priming effects on
mineralization of organic N to NH.,+, but that the ad
ditions of urea produced only a negligible priming
effect. It was reported that these effects increased with
increasing added N concentrations, but decreased as
temperatures were lowered. Crane (Crane W. 1972.
Urea-nitrogen transformations, soil reactions, and ele
mental movement via leaching and volatilization, in a
coniferous forest ecosystem following fertilization.
Ph.D thesis, Univ. of Washington, Seattle.) reviewed
impacts on cation exchange reactions which followed
the additions of urea to Pacific Northwest forest soils.
These impacts resulted largely from reductions in soil
acidity accompanying hydrolyses of the urea.
After N fertilization, N transformationsespecially
nitrificationmay be inhibited or accelerated by
changes in soil acidity (Alexander, 1977). For example,
applications of urea often decrease soil acidity, whereas
(NH.j)2SO., applications usually increase acidity. Addi
tions of lime with (NH4)2S04 to acid sandy soils re
sulted in nitrification after about 14 days (Eno and
Blue, 1957), but N03~ was not usually found after
fertilization of forest soils. The low levels of N03~ in
forest soils could mean that: (a) nitrification was not
occurring, or (b) N03_ was assimilated by microbes
and higher plants about as fast as it was formed, or (c)
denitrification was as rapid as nitrification, or (d) N03~
was transported vertically or laterally away from the
point of application soon after it was formed.
This study examined certain N transformations
and the extent of gaseous losses due to volatilization of
NH3 and denitrification after application of urea and
(NH4)2S04 to a flatwoods forest soil.
METHODS
The experimental treatments consisted of urea and
(NH4)2S04 at five levels (0, 100, 200, 300, 400 kg N
ha-1) and NH4 NOa at 200 kg ha-1 each replicated three
times in a randomized block design. Individual plots
were 5 x 10 m in size. The study was initiated in June
1978 within a 23-year-old slash pine plantation on a
Wauchula fine sand (sandy, siliceous, hyperthermic
Ultic Haplaquod) near Gainesville, Florida. Ammonia
volatilization measurements were made with four static
diffusion traps per plot, constructed from 4.2-cm diam
eter x 25-cm-long PVC tubes driven through the forest
floor and about 5 cm into the mineral soil. The upper
end of each tube was sealed with a rubber stopper, to
which was attached a glass microfiber paper pretreated
with 4% boric acid. The filter paper was changed on
a schedule as noted below.
Soil was sampled by horizons with a 4.5 cm soil
sampling tube and four cores from each plot were com
posited for each days determination of the treatment
effect. Soil and gas samples were collected 2, 4, 8, 12, 16,
21, 32, 64, and 128 days after fertilizer application. Soil
samples were frozen (10 C) until prepared for ex
traction with deionized water (1:5 ratio). After 1 hour
shaking time, the extract was filtered through millipore
(0.2 micron) units.
Total soil N and water extractable total N were
determined by micro-Kjeldahl (Nelson and Sommers,
1972), after NO, and N03~ were reduced and subse
quently distilled as NH4+ (Bremner, 1965). Urea in soil
extracts was estimated colorimetrically by the method
of Douglas and Bremner (1970). Extract pH was de
termined with a glass-membrane pH-sensitive electrode.
Cations were analyzed by atomic absorption and flame
emission spectrophotometry.
In two smaller experiments designed to compare de
nitrification from applications of urea, (NH4)2S04, and
NH4N03, three gas traps, constructed from 25-cm-
diameter PVC cylinders and driven 10 cm into the
surface soil, were placed in each treatment plot. Traps
remained open until sampling days when they were
sealed with plexiglass sheets against latex rubber rings
for 1 hour prior to sampling. Gas samples were col
lected periodically, through the plexiglass lid via serum
stoppers, and N,0 content of these samples determined
by gas chromotography with a N:65 electron capture
(EC) detector. Total denitrification was estimated by
multiplying the N20 concentration by the ratio of
N2-N:N,0-N of 10:1 (Ryden et ah, 1979; Rolston and
Broadbent, 1977). Precipitation reaching the forest
floor as throughfall was measured by a network of six
rain gauges on the study site (Fig. 1).
RESULTS AND DISCUSSION
The contrasting effects of urea and (NH4)2S04
fertilizers on soil pH are shown in Table 1. Applica
tions of (NH4)2S04 increased soil acidity by about half
a pH unit and this change in acidity persisted for
about 30 days after fertilization, during which there
were about 50 cm of rainfall. On the other hand, urea
fertilizer applications resulted in decreased acidity of
as much as two pH units and some changes in pH
persisted for 128 clays after fertilization.
Ammonia volatilization from the urea treatments
amounted to only 2 to 3% of the applied N over the
128-day period. Losses from (NH4)2SO., treatments
were much lower. Ammonia losses decreased exponen
tially with time after treatment. Although there was a
statistically significant effect of time and treatment on

Proceedings, Volume 39, 1980
21
20 40 GO 80 100 120
Fig. 1.Daily and cumulative rainfall collected beneath tree
canopy.
daily and cumulative NH¡¡ volatilization, the gross
amounts lost represented only a small percentage of
fertilizer N applied (Fig. 2 and 3).
Movement of N into the upper part of the mineral
soil prior to, or following, transformations was mark
edly affected by rainfall events. Daily and cumulative
TABLE 1.Water extract pH of forest floor (FF) and A1
horizons.
Fertilizer sources and rates (kg N ha-i)
Control Ammonium sulfate Urea
Days after 0 200 400 200 400
treatment FF Al FF A1 FI Al FF AI FF M
2 4.15 4.56 3.57 4.21 3.55 4.31 5.84 4.98 5.76 4.93
4 4.10 4.70 3.56 4.29 3.58 4.19 5.16 4.78 6.31 5.28
12 4.16 4.46 3.81 3.97 3.82 4.14 5.21 4.71 5.91 5.20
32 4.18 4.30 4.05 4.14 4.36 4.37 4.57 4.32 5.68 4.91
128 4.03 4.26 3.83 4.14 3.84 4.20 4.22 4.31 4.62 4.33
Time Since Feutiuz ation. (dam's)
Fig. 2.Daily ammonia volatilization.
O ZO 40 120
time since fEuriuzATioN (days)
Fig. 3.Cumulative NH^-N losses from nitrogen application.
rainfall for the duration of soil sampling are shown in
Fig. 1. Nitrogen (NH,+) from (NH4)2S04 appeared to
be more mobile than N from urea in this soil (Table
2). A possible explanation was the increased effective
exchange capacity brought about by the rise in pFI as
the urea hydrolyzed. Increased CEC enabled more of
the hydrolyzed urea to remain in the surface layers as
exchangeable NH4+. Another, and possibly more po
tent, effect was the presence of a strong anion (S04=)
in the (NH4),S04-treated soils. Because S04= ions are
only weakly adsorbed, they were available to leach with
the NH/.
In addition to the NH/, larger concentrations of
basic cations (Ca2+, Mg2+, K+, and Na+) were adsorbed
as a result of the increased effective CEC following
urea fertilization. Table 3 shows that total cations in
water extracts of this soil were low for urea-treated
samples, while (NH4)2S04 resulted in significant in
creases in total cations initially in solution, which
persisted through 12 days (or 75 mm of rain).
TABLE 2.Concentrations of NH -N in water extracts of the
4
forest floor during 128 days following fertilization with 400
kg N ha-i from ammonium sulfate and urea.
Time
Nitrogen source
since
Ammonium
treatment
sulfate
Urea
days
2
7605
2325
4
3640
704
8
4375
1114
16
1675
613
32
303
424
64
52
140
128
5
165

22
Soil and Crop Science Society of Florida
TABLE 3-Total cations (AW, Ca2+, Mg2' K1+, Nai+) in water
EXTRACTS OF FOREST FLOOR (TT) AND A1 HORIZONS.
Days
after
treatment
Fertilizer sources and rates (kg N ha-1)
Control Ammonium sulfate Urea
' 200 400 200 400
FF Al FF Al FF Al FF Al FF A1
/tg g-1 ODW
2
694
26
934
30
3101
35
180
25
315
25
4
444
19
1444
28
1990
39
190
25
180
11
12
425
15
851
43
1182
24
223
19
219
16
32
441
26
451
36
384
27
216
31
136
18
128
320
18
404
16
339
17
350
16
230
15
The increased pH which resulted from urea fer
tilization was expected to enhance conditions for
nitrification. Although little or no NO," + N03- was
detected in soil samples for the duration of the field
experiment, there appeared to be some minor trans
formation to N02- + N03" early in the sampling
period. This was indicated by the 1 to 3 kg N03-N ha-1
found in the A1 horizon at 2 to 4 days after fertilizing
with (NH4)2S04 or urea and the small increase in N,0
losses (Table 4). The low level of N03" in the soil does
not necessarily imply that nitrification was not taking-
place; it could mean that re-assimilation, leaching, or
denitrification depleted NO," + N03" almost as rap
idly as they were formed.
Denitrification certainly occurred, as indicated by
evolution of N,0, but it should be stressed that the
total gaseous evolution of N,0 was small. Applications
of ammonium sulfate at 400 kg N ha-1 resulted in a
maximum evolution of about 8 g N,0-N ha-1 day-1.
Urea at the same rate resulted in considerably higher
levels of N20, following an incubation phase (in the
soil), and immediately after a storm event (Fig. 4).
Total denitrification losses, which included N2 as
well as N,0, were doubtlessly considerable greater than
the levels indicated by N20-measurements alone. Be
cause of equipment limitations, only N,0 losses were
measured, even though much greater quantities of N2
than N,0 were assumed to have been lost. The as
sumed N:N,0 ratio of 10:1, mentioned previously,
TABLE 4.Nitrous oxide losses following applications of
NITROGEN FERTILIZERS TO A FOREST FLOOR.
Fertilizer sources and rates (kg N ha-1)
Days
after
Control
Ammonium
sulfate
Urea
Am
monium
nitrate
treatment
0
200 400
200 400
200
1
1.2
0.0
2
2.2
1.9
0.6
1.5
3
1.7
2.6
3.0
3.6
4.1
1.4
9
4.7
6.8
5.0
6.9
7.1
1.4
15
1.8
2.4
3.1
2.1
2.5

17
2.6
5.2
4.1
2.5
2.9
8.5
29
1.1
1.5
7.6
1.5
1.2
11.1
56
0.1
0.0
0.0
0.0
26.6
7.2
57




52.8
8.4
60
0.2
0.6
0.0
1.5
16.8
4.2
62
1.2
0.6
1.3
2.1
12.1

68
1.4
2.9
1.5
1.9
11.3

74
1.8
1.6
2.8
2.3
8.9

76
0.7
0.0
0.7
0.4
9.9
8.0
108




4.8

Fig. 4.Daily N O from urea and ammonium nitrate.
was supported by unpublished work of Krottje (per
sonal communication) who measured ratios from 10:1
to >100:1 in incubation studies. Therefore, for the
purposes of estimating total denitrification losses, a
ratio of at least 10:1 seemed appropriate. Table 4 lists
denitrification losses of N20 from various N fertilizers
and rates, expressed as grams per hectare of N,0-N per
day. Losses by denitrification were not significant for
(NH4),S04 (except for one event) nor for urea applied
at 200 kg N ha-1. Urea at 400 kg N ha-1 and NH, N03
applied at 200 kg N ha-1 (100 kg N03--N ha-1) resulted
in significantly more denitrification than either
(NH4)2S04 at 400 kg ha-1 (Table 4) or urea applied at
200 kg N ha-1 (Fig. 4).
Since (NH4),S04 and NH,,N03 were applied at the
same time and only NH,NO;i resulted in denitrifica
tion, the role of NOp availability in controlling the
rates of denitrification in this soil was confirmed. High
est levels of denitrification in these experiments were
50 g N,0-N ha-1 day-1, with background rates of 1 to
2 g NoO-N ha-1 day-1. These high rates of loss were
ephemeral, lasting for 1 to 2 days only, with inter
mediate rates persisting for 10 to 60 days. On the other
hand, Rolston and Broadbent (1977), working with a
fertilized agricultural soil, measured peak losses close
to 50 kg N2-N ha-1 day-1, arising from the fertilizer
applied.
CONCLUSIONS
Urea hydrolysis was rapid and subsequent NH3
volatilization amounted to only approximately 3% of
applied N.
Nitrate levels in the soil were very low throughout
the experimental period, despite the reduction in soil
acidity after urea applications.
Water-extractable NH/, Ca++, Mg++, K+, and Na*
decreased after fertilization with urea. This decrease
likely resulted from increased cation exchange capacity
brought about by the higher soil pH associated with
urea applications. Ammonium sulfate applications re-

23
Proceedings, Volume 39, 1980
suited in increased acidity and concurrent increases in
NHt* and other cations in solution.
A large part of the exponential decline in NH3
volatilization and concentrations of cations in soil ex
tracts following fertilization was related to cumulative
rainfall.
The low NO:1~ levels were thought to result from
low nitrification, rapid assimilation by microbes and
higher plants, denitrification, and leaching; but low
nitrification was probably the principal cause.
Estimated total denitrification, based on measured
N20 fluxes and an estimated N2:N20 ratio of 10:1, re
sulted in low N losses. Losses from urea, applied at 400
kg N ha-1, were only about 1% of the applied N. If,
however, a N2:N,0 ratio of 100:1 is assumed (which is
within the range of reality), up to 29% of applied
NH4N03 would have been lost during 100 days follow
ing fertilization. Nevertheless, leaching losses stemming
from frequent tropical summer storm events, rather
than gaseous losses, are likely to be responsible for a
major part of the unaccounted-for N from fertilization
of similar pine ecosystems.
ACKNOWLEDGMENT
The assistance of Owens-Illinois, on whose prop
erty the experiments were located, is acknowledged.
LITERATURE CITED
Alexander, M. 1977. Introduction to Soil Microbiology. 2nd ed.
John Wiley and Sons, Inc., New York.
Bremner, J. M. 1965. Inorganic forms of nitrogen, p. 1179-1237.
In C. A. Black (ed.) Methods of soil analysis. Agronomy 9.,
Am. Soc. of Agron., Madison, Wis.
Douglas, L. A., and J. M. Bremner. 1970. Extraction and
colorimetric determination of urea in soils. Soil Sci. Soc. Am.
Proc. 34:859-862.
Eno, C. F., and W. G. Blue. 1957. The comparative rate of
nitrification of anhydrous ammonia, urea, and ammonium
sulfate in sandy soils. Soil Sci. Soc. Am. Proc. 21:392-396.
Knowles, R. 1975. Interpretation of recent 15N studies of nitrogen
in forest systems, p. 53-65. In B. Bernier and C. H. Winget
(ed.) Forest 'Soils and Forest Land Management. Laval Univ.
Press, Quebec.
Mead, D. J., and W. L. Pritchett 1975. Fertilizer movement in a
slash pine ecosystem II. N distribution after two growing
seasons. Plant Soil 43:467-478.
Nelson, D. W and L. E. Sommers. 1972. A simple digestion pro
cedure for estimation of total nitrogen in soils and sediments.
J. Environ. Qual. l(4):423-425.
Ogner, G. 1972. Changes in the composition of raw humus and
the transport of organic matter as a result of urea fertiliza
tion. Proc. Int. Meet. Humic Substances, Nieuwershuis, Pudoc,
Wageningen.
Overrein, L. N. 1969. Lysimeter studies on tracer nitrogen in
forest soil: 2. Comparative losses of nitrogen through leaching
and volatilization after the addition of urea-, ammonium-,
and nitrate-i^N. Soil Sci. 107(3): 149-159.
Rolston, D. E., and F. E. Broadbent. 1977. Field measurement of
denitrification. Environ. Protect. Tech. Series. EPA-600/2-77-
233, U.S. EPA, Ada, Oklahoma.
Ryden, J. C., L. J. Lund, J. Letey, and D. D. Focht. 1979. Direct
measurement of denitrification loss from soils: 11. Develop
ment and application of field methods. Soil Sci. Soc. Am. J.
43:110-118.
Sarigumba, T. I., W. L. Pritchett, and W. H. Smith. 1976. Urea
and ammonium sulfate fertilization of potted slash pine under
two soil moisture regimes. Soil Sci. Soc. Am. J. 40:588-593.
Sarigumba, T. I., and J. G. A. Fiskell. 1975. Urea transformations
in two acid sandy soils. Soil Crop Sci. Soc. Florida Proc. 35:
150-155.
Volk, G. M. 1970. Gaseous loss of ammonia from prilled urea
applied to slash pine. Soil Sci. Soc. Am. Proc. 34(3):513-516.
Profile Distribution of Phosphate and Metals
in a Forest Soil Amended with Garbage Compost1
J. G. A. Fiskell and W. L. Pritchett2
ABSTRACT
Soil profile samples were taken from plots of
Myakka-Basinger fine sand that had received 0, 65, 130,
and 260 metric tons/ha of Gainesville municipal
garbage compost 2 years previously, applied either
broadcast and bedded or in the planting furrow. In
organic P, organic P, and metal distribution were de
termined. About 50% of the applied inorganic P was
converted to organic P and remained in the zone of
compost placement. Lack of P mobility was attributed
to adequate Fe and A1 in the soil surface horizons and
to additional Fe and A1 supplied in the compost.
Metals extracted by hot 0.1 N HC1 were primarily
distributed in the 0 to 23-cm depth; this coincided with
the distribution of course glass indicative of compost
placement whether broadcast or in the planting fur
row. At depths below 23 cm, metal levels from compost
treatments rarely exceeded those at corresponding
iFlorida Agricultural Experiment Stations Journal Series No.
2171.
^Professors, Soil Science Department, University of Florida,
Gainesville, Florida 32611.
depths of the control plots. At each rate of compost
amendment, the profile distributions were similar for
P, Cd, Cu, Mn, Pb, and Zn. Coarse material > 2mm
also contained high levels of these metals. There were
indications that roots in subsoil of the compost-treated
plots were higher in some metals than roots in control
plots.
Additional Index Words: Inorganic P, Organic P,
Metal mobility, Waste disposal, Nutrient movement,
FI a two od forests.
Recycling of municipal garbage compost in order
to reclaim nutrients otherwise lost in landfills has not
become a popular practice mainly because unsightly
residues or disagreeable odors create an unfavorable
impression on nearby residential areas. Such objections
can be largely avoided by applications of the compost
to more remote land planted to forest where residues
can be reduced by incorporation in the planting beds
and subsequently covered by forest litter. Where this
practice has been used (2, 4), weed growth and under
story shrub growth competed strongly with the

24
Soil and Crop Science Society of Florida
planted pine during the first 5 years. Nevertheless, in
such a planting at the Austin Carey forest near Gaines
ville, both tree height and diameter increased more
rapidly where garbage compost had been applied than
in the control plots (4). During this period, levels of
N, P, and metals in the pine foliage increased linearly
with rate of compost application. However, there were
few differences between surface broadcast and bedding-
compared to placement in a planting furrow and then
bedding (4). The present study determined the
amounts and distribution of P and metals from the
garbage compost that remained in the soil profile after
8 years.
MATERIALS AND METFIODS
The experiment was conducted at the Austin Carey
forest near Gainesville. The cleared forest site was
composed of Myakka (sandy, siliceous, hyperthermic
Aerie Haplaquod) and Basinger (sandy, siliceous,
hyperthermic Spodic Psammaquent) fine sands in
which the degree of development of the Bh horizon
was a principal difference between the two series. Both
soils had an initial soil pFI ranging from 4.3 to 4.5.
The municipal garbage compost (58% moisture) was
obtained from the Gainesville, Florida, plant and was
either spread broadcast over the plot (each 0.081 ha)
with subsequent disc incorporation into four planting
beds (BD) or was placed in planting furrows over
which beds were contructed (IF). The rates were 65,
130, and 260 dry metric tons per hectare (mt/ha) in
three randomized blocks, each consisting of the six
treatments and a control. Year-old slash pine seedlings
were planted 5 months after compost amendment in
rows 3 m apart.
At 8 years after treatment, soil samples were taken
using a hydraulic-driven tube with a 7.7 cm diameter
located at the bed center between trees. Three cores
taken per plot were combined for the 0 to 8 cm, and
subsequent 15-cm depths to a depth of 83 cm, and kept
in polyethylene bags. The samples were processed
through a 2-nnn sieve. Coarse compost residue and
roots remaining on the sieve were dried, weighed, and
ashed at 350 C for 90 minutes followed by heating at
550 C for 90 minutes. The ash was weighed and dis
solved in IN HC1 and analyzed for metals by atomic
absorption spectroscopy.
The soil passing the sieve was air-dried and mixed
on a plastic sheet. To determine inorganic P, 5-g sub
samples were placed in 50 ml of 0.1IV HC1 in Pyrex
tubes, heated in a water bath at 98 C for 3 hours, then
filtered through No. 42 Whatman paper, and washed
with a further 50 ml of hot 0.LV FIC1 as proposed by
Saunders and Williams (6). For organic P, the paper
was washed several times with water and then trans
ferred to 200 ml of 0.1IV NaOH and shaken inter
mittently at 20 C for 16 hours. A 20-ml aliquot was
pipetted into a 150-ml beaker and evaporated to dry
ness. Acid digestion of the sample proceeded in a suit
able fume hood with 1 ml of perchloric acid and 10 ml
of concentrated HN03 heated until all organic matter
disappeared, and where organic matter persisted, addi
tional HN03 and a few drops of 30% H202 were
added for complete digestion. The sample was diluted
with 50 ml of water, titrated with 0.1N NaOH to pH
3 and analyzed for P by the ascorbic acid molybdate
method. This P fraction has previously been reported
as organic P (1,6).
Other 5-g soil samples were ashed at 350 C for 2
hours and at 500 C for 2 hours in crucibles which then
received 2 ml concentrated HN03 at low heat. Transfer
of ash to filter paper was made with 0.2N H2S04 in
repeated rinsings, and the filtrates made to 100-ml
volume. These solutions were analyzed for total P by
the above colorimetric method and the difference be
tween total P and inorganic P was also termed
organic P (3). To confirm the completeness of P re
covery, many of the residues from the ashed samples
received 0.5 g Na2C03, prior to reashing at 550 C.
These were ground in a mortar and then 0.5 g of the
sample was fused with 5 g of Na2C03 in a Pt crucible.
The melt was dissolved in LON HC1 made to 100 ml
volume in 0.1 Ar HC1 and analyzed for P, Ca, Al, and
Fe.
Metal contents of the O.llV HC1 extracts and the
0.2N H,S04 extracts were determined by atomic ab
sorption or using the graphite furnace HGA 2100 and
Perkin-Elmer 503 unit where necessary for greater
accuracy at low Cel and Cu values. Data were statistic
ally analyzed for effect of rates and placement on P
and metal values with depth and comparison of meth
ods for determination of organic P.
RESULTS AND DISCUSSION
Municipal garbage compost at the rates used in this
study (Table 1) added high levels of N, P, and metals.
Both slash pine and under- story species showed ob
vious response to compost addition, particularly to the
intermediate rate during the first few years (2) and
good response was noted in other species (5). However,
only a small portion of the nutrients added was in
volved in plant uptake, because heavy metal com
pounds in soils have low solubilities. The remainder
was probably present in various unavailable forms.
Factors expected to influence P and heavy metal move
ment from the site of compost placement were time,
soil acidity, and formation of water-soluble ions and
complexes. At soil pFI 5.0 (4) and after 8 years, soil
samples taken below the zone of compost placement
should contain P or metal accumulations if leaching
occurred, and be expected to concentrate in the Bh
TABLE 1.Composition of Gainesville municipal garbage com
post AND AMOUNTS OF ELEMENTS ADDED PREPLANT TO MYAKKA-
BASINCER SOIL AT AUSTIN CAREY FOREST.
Composition Compost added, mt/ha
Component
Content
65
130
260
ppm
kg/ha
Soluble salts
1,450
95
189
377
Total N
7,100
462
923
1,846
Inorganic P
1,730
113
225
450
Organic P
336
21
43
87
Al
6,550
425
850
1,700
Fe
4,600
300
600
1,200
Ca
19,100
1,242
2,483
4,966
Mg
1,700
112
221
442
K
2,300
150
299
598
Cd
42
2.7
5.5
11
Cu
155
10
20
40
Mn
328
21
43
85
Ni
68
4.5
9
18
Pb
613
40
80
159
Zn
985
64
128
256

25
Proceedings, Volume 59, 1980
horizon. Since a large amount o£ energy was supplied
in compost material for heterotropic organisms, avail
ability of both P and heavy metal compounds could be
expected to be altered by microbial processes. However,
the effect of microbial immobilization on leaching is
unknown.
Phosphate: Conversion of inorganic P supplied by
the compost (Table 1) to organic P forms indicated
microbial incorporation had occurred (Table 2). The
direct method for organic P (as determined in cold
0.1 A NaOH extracts) showed a very high correlation
(r = 0.97 or better) at each soil depth to that found
by the indirect method obtained by the difference be
tween total P of ashed samples and that extracted by
hot 0.1 A HC1 extraction. The indirect method always
gave from 1 to 2 ppm of P more than that found by the
direct method. This is a rather small difference con
sidering the magnitude of P values in Table 2. This
is in contrast to greater differences between these meth
ods found for other soils (3, 7).
There were no significant increases from treatment
either in inorganic P at depths below 38 cm or in or
ganic P at depths below 23 cm. Since the spodic horizon
was generally located at 53 to 68-cm depth, any move-
TABLE 2.Inorganic and organic P distributions in sandy soil
PROFILES SAMPLED 8 YEARS AFTER MUNICIPAL GARBAGE COMPOST
AMENDMENT.
Garbage compost rate and placement, mt/haf
Depth
0
65
65
130
130
260
260
sampled
BD
IF
BD
IF
BD
IF
cm
kg/ha
Inorganic P¡¡¡
0-8
14
38
40
65
21
61
157
8-23
18
117
221
275
38
60
94
23-38
15
52
57
21
30
35
33
38-53
38
35
28
23
15
20
33
53-68
26
28
32
25
27
33
53
68-83
31
24
32
27
20
33
38
Profile
142
294
410
436
151
242
408
Organic P§
0-8
21
- 42
36
53
24
52
186
8-23
25
54
182
192
42
52
68
23-38
27
42
47
28
32
28
45
38-53
76
36
42
32
36
48
56
53-68
56
67
44
39
80
75
84
68-83
37
44
37
34
28
38
38
Profile
242
285
388
378
242
293
477
Recovered P
0-8
35
80
76
118
45
113
343
8-23
43
171
403
467
80
112
162
23-38
42
94
104
49
62
63
78
38-53
114
71
70
55
51
68
89
53-68
82
95
76
64
107
108
137
68-83
68
68
69
61
48
71
76
Profile
382
579
798
814
393
535
885
Applied P
134
134
268
268
537
537
Recovered PControl P
197
416
432
11
153
503
+BD is broadcast and bedded and IF is placement in furrow
before bedding.
¡¡¡Determined by hot 0.1 A1' HC1 extraction.
(¡Determined sequentially by cold 0.11V NaOH extraction.
ment of P from the upper surfaces should have re
sulted in P accumulation at this depth. However, there
was no evidence of any such accumulation. Amounts
of A1 and Fe throughout the profile (Table 3) were
probably sufficient to sorb P. From comparison of total
P recovered from the soil profile (Table 2) to that
applied, it is obvious that soil samples diet not ac
curately reflect the compost rate and placement treat
ment. This was attributed to lack of uniformity during
compost spreading and to difficulty in positioning the
power sampler exactly at the center of the bed. The
inorganic to organic P ratio at the 0 to 8-cm depth was
0.69 in the control plots compared to a range from
0.85 to 1.23 for amended soil. At the 8 to 23-cm depth,
corresponding rates were 0.72 for the control and a
range from 0.89 to 1.43 for treated soil. It was evident
that conversion of inorganic P to organic P had oc
curred over an 8-year span and that this P showed
little evidence of mobility in contrast to preferential
organic P mobility reported in other soils (7).
Since effect of compost placement on inorganic P
was independent of compost rate at the 0 to 8-cm
depth, the significant (0.05 level) rate effect on in
organic P was found to be
P= 5.23 + 20.8 R [1]
where R is compost rate/65 mt/ha. However, at the 8
to 23-cm depth both inorganic and organic P were
found to have significant quadratic responses to rate
of compost within the rate X placement interaction.
Locating compost placement: Further explanation
for the variability in P data was obtained by examining
the distributions of Fe, Al, Ca, and crushed glass
(Table 4). At the 0 to 8-cm depth, Ga significantly in
creased with compost rate:
Ca = 7.17 + 360.4 R, [2]
whereas at the 23 to 38-cm depth, Ca decreased signif
icantly with compost rate:
Ca = 405 67.2 R. [3]
This may be explained by deeper placement at the
lower rates than at the higher rates, suggested by the
large differences in Ca at the shallower depths in the
six treatments. The Al and Fe values in the 0 to 23-cm
depths showed similar pattern of changes in magnitude
as those for Ca. For instance, at the 8 to 23-cm depth,
Fe values also decreased with compost rates:
Fe = 521 -79.5 R. [4]
Presence of crushed glass accounted for the major
differences in ash from the coarse soil fraction (Table
4), with values always being highest at the shallower
depths. This coarse glass associated with the compost
was present where coarse ash exceeded 2.5 g/kg soil,
magnitude of changes at 0 to 38-cm depth being like in
pattern to those for other components (Tables 4 and
5). Grams of coarse ash (AW) for the whole composite
core sample resulted in highly significant response for
the placement X rate interaction. For BD placement,
the relationship was
AW = 130 + 292 R 61 R2. [5]
For IF placement it was
AW = 401 + 270 R + 46 R-, [6]
, r
whereas corresponding ash weight for the control at

26
Soil and Crop Science Society of Florida
TABLE 3.Dominant soil series organic matter, total Fe and A1 in control and compost-
amended PROFILES.!'
Depth
sampled
Horizon
Organic matter^
Fe§
Al§
0
260 mt/ha
0
260 mt/ha
0
260 mt/ha
cm
_ %
Myakka fine sand
0-8
Ap
1.44
3.80
132
2,550
260
3,800
8-23
Ap
2.67
2.01
146
270
140
480
23-38
A22
1.32
1.35
148
110
460
620
38-53
B21h
1.91
0.86
194
71
2,680
2,750
53-68
B22h
0.86
1.58
152
240
1,480
2,000
68-83
C
0.66
1.25
148
130
1,800
1,450
Basinger fine sand
0-8
Ap
1.32
1.78
132
460
300
2,050
8-23
Ap
1.65
1.65
146
690
300
2,400
23-38
A22
0.83
0.96
144
290
460
1,550
38-53
C & Blh
0.83
0.96
260
270
1,500
1,910
53-68
C & B2h
0.74
0.92
124
150
740
860
68-83
C2
0.60
0.73
54
92
940
650
fMean for 3 replicates of composite cores sampled from center of the bed.
^Determined by dichromate- concentrated H SO oxidation.
§Determined after concentrated HN03
digestion and 0.2N H2S04 extraction of soil ashed at 550C.
TABLE 4.-
-Distribution
of Fe, A1 Ca,
AND COARSE ASII IN
SANDY SOIL 8
YEARS AFTER
MUNICIPAL
GARBAGE COMPOST AMENDMENTS.
Garbage compost rate and placement, mt/ha
S.E.
Depth
65
65
130
130
260
260
of
sampled
0
BD
IF
BD
IF
BD
IF
mean
cm
Fe, ppmf
0-8
139
285
173
184
159
287
343
61
8-23
100
440
440
540
187
245
159
56
23-38
68
293
246
118
165
121
147
49
38-53
55
147
41
95
139
89
95
39
53-68
43
102
65
87
100
77
129
23
68-83
61
79
43
58
81
55
87
12
Al, ppmf
0-8
227
410
267
274
540
567
940
129
8-23
187
373
540
720
550
440
300
90
23-38
433
313
353
370
730
421
627
125
38-53
1,680
880
880
693
970
767
740
183
53-68
1,510
1,630
1,220
653
850
900
960
191
68-83
960
1,130
1,000
647
635
653
567
162
Ca, ppmf
0-8
156
593
553
653
235
713
2,370
292
8-23
93
813
1,270
1,570
267
487
387
88
23-38
46
331
417
190
246
123
187
04
38-53
30
65
132
90
39
49
87
17
53-68
10
49
70
86
29
33
133
28
68-83
25
19
35
31
14
67
62
14
Coarse ash, g/kg soil
0-8
2.5
10.6
7.9
3.1
4.9
7.1
7.0
8-23
1.8
20.0
15.1
10.8
3.7
12.8
3.9
23-38
1.0
10.1
7.0
7.4
3.5
3.3
2.2
38-53
1.3
2.9
1.9
0.5
0.5
1.8
0.9
53-68
0.8
2.0
2.0
0.9
0.5
0.7
0.7
68-83
1.1
0.4
2.4
0.4
0.2
1.0
0.8
fExtracted by hot O.hV HC1 for 3 hours.

27
Proceedings, Volume 39, 1980
TABLE 5.Metal distributions in sandy soil sampled 8 years
AFTER MUNICIPAL GARBAGE COMPOST AMENDMENTS.>¡*
Depth
sampled
Garbage compost, mt/ha
S.E.
of rate
mean
0
65
130
260
Zinc
0-8
5.8
41.5
34.7
44.6
31.7
8-23
4.3
80.0
124.0
25.3
12.4
23-38
4.7
32.9
5.8
6.8
7.3
38-53
3.3
6.3
5.9
3.3
0.9
53-68
5.0
11.0
6.1
4.4
4.2
68-83
7.0
7.9
7.4
5.4
1.8
Copper
0-8
0.48
4.33
128.00
15.90
3.72
8-23
0.80
7.27
12.90
2.88
0.44
23-38
0.43
1.19
0.85
0.79
0.09
38-53
0.58
0.53
0.61
0.47
0.01
53-68
0.48
0.53
0.76
0.71
0.04
68-83
0.37
0.55
0.89
0.06
0.01
Cadmium
0-8
0.063
1.730
2.070
0.933
0.61
8-23
0.047
1.088
4.600
0.306
1.18
23-38
0.051
0.751
0.057
0.047
0.44
38-53
0.031
0.040
0.028
0.004
0.01
53-68
0.073
0.045
0.069
0.004
0.02
68-83
0.053
0.035
0.007
0.005
0.01
Manganese
0-8
2.3
24.9
15.4
18.6
11.73
8-23
0.7
23.3
47.3
8.8
3.60
23-38
0.7
6.9
1.8
1.3
1.89
38-53
0.7
1.0
1.9
0.8
0.51
53-68
0.5
0.8
1.5
0.7
0.98
68-83
0.7
0.7
0.6
0.7
0.26
Lead
0-8
0.10
31.30
20.00
48.00
12.30
8-23
0.01
41.70
62.70
16.70
8.08
23-38
0.01
23.30
7.40
0.70
6.46
38-53
0.01
0.01
0.10
0.10
0.07
53-68
0.01
0.01
0.01
0.01
0.01
68-83
0.01
0.01
0.01
0.01
0.01
[Determined by hot 0.IN HC1 extraction for 3 hours; BD
samples only shown.
this depth was 11 grams. Failure to obtain a good fit
between treatment application and composite core
data was attributed to (i) differences in compost com
position which was not from a single plant run, (ii)
irregularity in compost spreading, (iii) lack of uni
formity of IF placement, and (iv) difficulty in taking
core samples representative of this variability.
Heavy metals: Heavy metal distributions in the
profile (Table 5) showed increases in metal content at
the 0 to 38-cm depths where compost had been applied
compared to similar depths in the control plots. There
was no statistical difference among values at depths
below 38 cm. Few statistically significant differences
between compost rates were found for any of these
metals because the standard errors for rate means were
relatively high. Only very small amounts of heavy
metals appeared to have moved below the depth of
compost placement. Where compost rate X placement
responses were significant, these occurred at the 8 to
23-cm depth. For BD placement (Table 5), three
metals showed the following significant responses for
rate of compost:
Zn = -26 + 137 R-31 R2, [7]
Mn = -27 + 67 R 14 R2, [8]
and Pb = -41 + 104 R 22 R2, [9]
where R is compost rate/65. Shape of response curves
for Eq. 7-9 was similar to that for ash weight in Eq.
[5], which confirms that sampling did not represent
well the variability for compost placement.
Metals in coarse fraction: In the material > 2mm
designated as coarse material, weight and analyses are
given in Table 6. Roots comprised most of the sample
weight below 38 cm. Contrary to quantity of metals
recovered from the treated soil, roots contained higher
amounts of Cd, Cu, Mn, Pb, and Zn at depths below
38 cm than the soil from control plots, regardless of
TABI.E 6.Metal composition of coarse fraction in sandy soil
PROFILES SAMPLED 8 YEARS AFTER MUNICIPAL GARBAGE COMPOST
AMENDMENTS.!'
Depth
Garbage compost, mt/ha
sampled
0
65
130
260
cm
0.8
Fraction weight, g/kg soil
11.1 16.3 5.0
9.8
8-23
3.4
18.2
16.2
18.1
23-38
1.7
13.3
11.1
5.3
38-53
2.8
4.2
0.9
2.6
53-68
1.1
3.3
1.2
1.1
68-83
1.6
0.7
0.6
1.5
0-8
0.2
Cd, ppm
2.49
4.13
2.36
8-23
0.01
3.48
7.36
7.97
23-38
0.01
6.92
4.01
0.42
38-53
0.01
0.17
0.79
3.05
53-68
0.01
0.56
1.84
0.24
68-83
0.01
2.82
0.12
0.20
0-8
1.6
Cu, ppm
25.8
8.2
123.0
8-23
1.3
38.5
102.0
12.1
23-38
0.6
14.8
8.8
8.8
38-53
0.5
0.9
2.5
4.0
53-68
0.3
1.3
3.5
1.2
68-83
0.2
2.3
0.6
0.7
0-8
17.7
Mn, ppm
35.2
27.5
20.9
8-23
6.0
30.5
65.3
22.2
23-38
3.7
34.7
32.6
1.8
38-53
3.7
2.3
8.9
3.8
53-68
2.0
10.4
11.1
3.5
68-83
1.5
10.5
4.1
2.8
0-8
6.1
Pb, ppm
34.4
71.5
41.0
8-23
4.9
78.9
138.1
57.0
23-38
2.1
209.0
28.8
23.2
38-53
1.5
3.0
32.1
5.6
53-68
0.8
1.3
12.4
4.4
68-83
0.6
1.4
2.9
3.3
0-8
17.5
Zn, ppm
77.4
94.6
77.5
8-23
6.6
193.0
186.0
74.1
23-38
4.6
402.0
142.0
18.7
38-53
3.6
9.7
13.0
20.8
53-68
2.1
14.1
25.1
25.2
68-83
1.5
23.0
2.4
18.3
fCoarse fraction dried at 100 C, ashed at 550 C and dissolved
in HC1.

28
Soil and Crop Science Society of Florida
root weight. This suggested that metals at these depths
were accumulated on or in the roots, perhaps during
mass How of soil solution to the roots. Roots account
for small amounts metals moved below the 38-cm
depth. However, heavy metals present in the coarse
fraction above 38-cm depth were relatively higher than
those shown in Table 5. This suggested that much of
the metal present in the compost had not reacted with
the soil; perhaps much remained in metallic state, as
observed for copper wire in a few samples.
Implication of finding: Soil samples taken at 8
years after compost treatment and those taken 18
months previously (4) showed that very little metal
movement below 38 cm had occurred. However, in the
earlier study with a small diameter tube, metal values
for IF placement exceeded those for BD placement at
0 to 38-cm depths as might be expected, whereas this
was not the case for the larger diameter tube. Con
siderable variability of compost placement was evi
dent, so that monitoring of both P and metal distribu
tion in subsequent years produced problems of within-
plot variation. Other than the lush growth of under
story species competing with pine growth prior to
canopy closure, no adverse effects on forest growth has
been determined. To date, significantly better pine
tree growth has been associated with soil amended with
garbage compost than that in control plots. As forest
litter accumulates, and further reaction of soil and
compost occurs, further monitoring of the site will be
valuable in understanding long-term effects from land
spreading of waste materials on forestlands, and forest
nutrition.
LITERATURE CITED
1. Anderson, G. 1960. Factors affecting the estimation of phos
phate esters in soil. J. Sci. Food Agrie. 11:497-503.
2. Bengtson, G. W and J. J. Cornette. 1973. Disposal of com
posted municipal waste in a plantation of young slash pine:
Effects on soil and trees. J. Environ. Qual. 2:441-444.
3. Dormaar, J. F and G. R. Webster. 1964. Losses inherent in
ignition procedures for determining total organic phosphorus.
Can. J. Soil Sci. 44:1-6.
4. Fiskell, J. G. A., W. L. Pritchett, M. Maftoun, and W. H.
Smith. 1979. Effects cf garbage compost rates and placement
on a slash pine forest and metal distribution in an acid sand,
p. 302-313. In Second Ann. Conf. of Applied Research and
Practice on Municipal and Industrial Waste, Madison, Wis.
5. Hortenstine, C. C., and D. F. Rothwell. 1972. Use of munic
ipal compost in reclamation of phosphate-mining sand tail
ings. J. Environ. Qual. 1:415-418.
6. Saunders, W. M. H., and E. G. Williams. 1955. Observations
on the determination of total organic phosphorus in soil.
J. Soil Sci. 6:254-267.
7. Williams, E. G., and W. M. H. Saunders. 1956. Distribution
of phosphorus in profiles and particle-size fractions of some
Scottish soils. J. Soil Sci. 7:90-108.
Evaporation Effects on Sprinkler Irrigation Efficiencies1
Allen G. Smajstrla and Richard S. Hanson2
ABSTRACT
A numerical simulation model was developed to
study the effects of various sprinkler irrigation manage
ment strategies on crop-water use efficiencies. This
model allows the user to simulate the scheduling of
irrigations for crop production. Model inputs required
are descriptions of climatic, crop, and soil conditions,
specifically including daily rainfall, pan evaporation,
soil-water capacity function, crop effective rooting
zone, and water use coefficients versus growth stage.
This model simulates a daily soil-water balance and
crop-water use, assuming that soil-water contents do
not decrease transpiration rates. In this work, four
levels of soil-water depletion and three magnitudes of
irrigation depths were studied. Seasonal irrigation re
quirements were found to decrease with both greater
allowable water depletions and with smaller depths of
application. This was due to effective rainfall increas
ing with the same components. Seasonal evaporation
losses were found to be unaffected by depth of applica
tions and only mildly affected by decreases in allow
able water depletions. This resulted because evapora
tion rates remained fairly high due to frequent rain
storms.
Gross water requirements were found to be less for
an intermediate application depth, because evapora
iFlorida Agricultural Experiment Stations Journal Series No.
2301.
2Assistant Professor and Student Research Assistant, respec
tively, Agricultural Engineering Department, University of Flor
ida, Gainesville, FL 32611.
tion and interception losses were great for small, fre
quent applications, and because effective rainfall was
low for large, infrequent applications. The optimum
is specific for a given set of soil, crop, and climatic
conditions.
Additional Index Words: Simulation, Computer
model, Evapotranspiration, Effective rainfall.
Sprinkler irrigation efficiencies are always less than
100% because losses occur as water is sprayed through
the air, as water is evaporated from the crop canopy
(interception losses), and as water is evaporated from
the soil surface rather than being transpired by the
crop. Other losses such as those due to deep percola
tion and runoff may reduce irrigation efficiency. How
ever, the latter losses may be completely eliminated by
proper system design and management, whereas evap
oration losses are unavoidable and can only be min
imized by good system management.
The objective of this study was to simulate various
irrigation management strategies for crop, soil, and
weather conditions typical of north central Florida.
Specific data were selected for each of these conditions
because of their unique combination at this location.
Specific objectives of this study included:
1. To develop a numerical model to simulate field
water cycles for irrigated crop production.
2. To determine the effects of soil evaporation, soil
hydraulic properties, and irrigation management
practices on irrigation and water use efficiences.

Proceedings, Volume 39, 1980
29
MATERIALS AND METHODS
A numerical model was developed to simulate the
interactions of the various components of the hydro-
logic cycle for irrigated crop production. Components
of the hydrologic cycle which were simulated by the
model are illustrated in Fig. 1. They included rainfall,
irrigation, evaporation, transpiration, and deep perco
lation.
The numerical model was developed in general
terms so that it would be applicable to studies of irri
gation efficiencies for various crops and soil types. Data
inputs were classified as weather, soil, or crop data.
Weather inputs included daily rainfall and pan evapo
ration data. The soil input was the water capacity
curve. Crop inputs included the functional relation
ships between stage of growth and (1) leaf area index,
(2) effective rooting depth, and (3) water use coefficients.
In this study, sprinkler irrigation efficiency was simu
lated for soybeans (Glycine max (L) Merr.) produced
on Lake fine sand (hyperthermic, coated, Typic
Quartzipsamment) with weather conditions measured
at Gainesville, Florida.
A flow chart of the numerical model is shown in
Fig. 2 (A complete listing of the numerical model is
available from the senior author upon request). Each
simulation began with the input of soil, crop, and
weather data. Those requirements are described in
detail in the following paragraphs.
Leaf area index was calculated in the first compu
tational step. Leaf area index as a function of time was
obtained from studies conducted at the Institute of
Food and Agricultural Sciences (IFAS Irrigation Park
at Gainesville (K. Boote, personal communication).
That function is presented in Fig. 3.
Effective rooting depth was calculated for the ex
isting stage of crop growth. Data of Robertson et al.
(1979) were used to determine maximum depths for
local conditions. Because of the lack of details on root
development versus stage of crop growth, data of
Burch et al. (1978) were also used. Those data are
shown in Fig. 4.
Available soil moisture was calculated as a func-
SOIL- PLANT-ATMOSPHERE SYSTEM
COMPONENTS
Fig. 1.Components of the soil plant atmosphere system
model.
tion of the soil hydraulic properties and effective root
ing depth. The water capacity curve for Lake fine sand
is given in Fig. 5. From this figure, available soil mois
ture on a volumetric basis was estimated. Because of
Fig. 2.Flow chart for the soil plant atmosphere system
model.
Fig. 3.Leaf area index function for soybeans.
Fig. 4.Rooting depth function for soybeans.

30
Soil and Crop Science Society of Florida
the dynamic effects of soil-plant-atmosphere-water in
teractions, available water is not a constant, but is de
pendent upon the interactions of those factors. There
fore, in this work, a range of values was used in order
to study the effects of available water on irrigation
efficiencies. It was assumed that no reduction in crop
growth or yield would occur until after all readily
available soil moisture was depleted. As shown in Fig.
5, the lower limit of the readily available water range
was assumed to occur at approximately 1 bar of capil
lary suction and a volumetric water content of 0.05.
Irrigations were scheduled when all readily available
soil moisture was depleted, so that stress did not oc
cur and production was optimized with respect to
water use.
Evaporation from wet foliage does not greatly ex
ceed normal evapotranspiration rates (Christiansen
and Davis, 1967, and Pair, 1969). It is, however, a func
tion of amount of canopy cover. In this model, inter
ception of rainfall and sprinkler water by the crop
canopy was calculated as a function of leaf area index.
A maximum of 0.25 cm of interception was calculated
for a leaf area index of 6.0 or greater. Interception was
assumed to vary linearly with leaf area index at mag
nitudes of less than 6.0.
Deep percolation losses were calculated from a mass
balance of the water content in the crop rooting zone.
Rainfall depths greater than those necessary to restore
the crop rooting zone to field capacity were assumed
to cause deep percolation, thus becoming unavailable
to the crop.
The soil-water status and effective rainfall were
calculated after each rainfall event. Effective rainfall
was calculated as the total depth of precipitation that
was stored in the crop rooting zone after each rainfall
event. The soil-water status was defined as the depth of
water stored in tire crop rooting zone on a daily basis.
Transpiration rates were calculated on a daily basis
as a function of pan evaporation. Data from National
Weather Service records were used for this purpose.
Crop water use coefficients as a function of time were
VOLUMETRIC WATER CONTENT
Fig. 5.Water capacity function for Lake fine sand.
obtained from SCS Technical Release 21 (1970) and
are given in Fig. 6. Transpiration was assumed to oc
cur at non-water-limiting rates throughout the grow
ing season because irrigations were scheduled when
ever the readily-available soil-water was depleted.
Soil evaporation rates were calculated as a function
of soil hydraulic properties, pan evaporation, and leaf
area index. Ritchie (1972) reported that when the soil
surface is wet, energy at the soil surface and soil-
hydraulic properties limit evaporation. The functions
presented by Ritchie (1972) were used in this work.
Daily evaporation rates were calculated from
Ep = (r/a) ETp, (1)
where Ep = daily evaporation rate for non-water-
limiting conditions (cm/day),
t = dimensionless radiation interception
factor for the crop canopy,
a = dimensionless crop and climate propor
tionality factor, and
ETp = energy-limited ET from a well-watered
surface during non-advective condi
tions.
The numerical value of r was calculated from
r = exp (0.398LAI), (2)
where LAI = leaf area index.
Equation 2 was developed by Ritchie (1972) for
sorghum, and later verified as applicable to soybeans
by Kanemasu et al. (1976). The value of a used was
1.26. That value was established by Priestly and
Taylor (1972) after evaluating 11 different non-advec
tive climatic conditions.
Evaporation from the soil surface was calculated
to occur at the non-water-limiting rate given in Equa
tion 1 through the first stage drying of the soil surface.
First stage drying was assumed to occur for a period of
1 day following rainfall. This assumption was verified
by experimentation at the IFAS Irrigation Park.
After first stage drying, the method of Black et al.
(1969) was used to evaluate losses during falling-rate
stages. For drying of Plainfield Sand, they developed
the following empirical relationship;
E = c/t0-5 (3)
where E = daily evaporation rate (cm/day),
GROWING SEASON (DAYS)
Fig. 6.Soybean growth coefficient function.

31
Proceedings, Volume 39, 1980
c = constant o proportionality for given soil
conditions, and
t = time since beginning of drying cycle (days).
The value of c was defined by Equation 4, which
results from an analytical solution of the one-climen-
sional water flow equation for isothermal flow in a
homogeneous soil-profile (Black et ah, 1969).
c = 2 (Mo) (DA)-5 (4)
where = field capacity volumetric water content,
60 = air dry volumetric water content, and
I) = weighted mean diffusivity (cm2/day).
In equation 4, di for Lake fine sand was assumed to
0.12 (Fig. 5), d was assumed to be 0, and the value of
D was assumed to be 13 cm2/day (Black et ah, 1969).
The value of c was then 0.49 cm/day0-5 for the condi
tions of this study.
The soil-water was updated daily by mass balance,
including evaporation and transpiration depletions.
The decision concerning irrigation scheduling was
made on the basis of the soil-water status. Irrigations
were scheduled when the total soil-water storage in
the plant root zone reached a predetermined critical
level. In this study, four critical levels were investi
gated, and irrigations were scheduled at water deple
tions of 1%, 3%, 5%, and 7% water contents on a
volumetric basis. The 1 % level represented almost
daily irrigations, while the 7 % level represented al
most complete depletion of readily available soil-water.
The 3% and 5% levels were within the range of com
mon irrigation management practices on sandy soils
similar to Lake fine sand.
Three depths of irrigation were simulated to oc
cur. These were 1-cm and 3-cm applications, and a
variable application of sufficient depth to restore the
soil profile to field capacity. These values were chosen
in order to simulate the range the irrigation depths
that could occur. Irrigation interception losses were
calculated as functions of the canopy leaf area index
as rainfall was. Evaporation losses which occur because
water is sprayed through the air are functions of the
evaporative demand and type of irrigation systems used
(Pair, 1969). In this work those evaporation losses were
calculated as 10% of the depth of irrigation (Pair,
1969).
Weather inputs consisted of daily rainfall and pan
evaporation values. Rainfall data were nsecl to update
the soil-water status on a daily basis, and pan evapora
tion data were used on an index of potential evapo-
transpiration and crop-water use. Because rainfall dis
tributions are critical to irrigation management strat
egies, 10 years of daily weather data from National
Weather Service records were used to evaluate the
long-term effects of precipitation distributions for
Gainesville.
RESULTS AND DISCUSSION
The simulation model illustrated in Fig. 2 was
used to study the effects of various irrigation manage
ment strategies on irrigation requirements and water
use efficiency for soybean production on Lake fine sand
at Gainesville, Florida. Actual weather records for a
10-year period of time were used in this study, and all
results are presented as the averages of ten simulated
growing seasons.
Figure 7 illustrates the effects of four water deple
tions and three irrigation application depths required
during the growing season. Smaller applications re
quired more numerous applications. Also, as allow
able water depletions were decreased before irrigations
were scheduled, larger numbers of irrigations were re
quired.
In Fig. 8, the effects of the management decisions
on seasonal soil water requirements are shown. The
greatest amount of water was required to be supplied
at all depletion levels by the practice of replenishing
the entire soil profile to field capacity (NWD prac
tice). This occurred because irrigations at the l-cm and
3-cm levels (below NWD) allowed for storage of some
of the precipitation which occurred immediately after
irrigations. Therefore, rainfall became more effective
in contributing to crop water requirements. Also,
greater amounts of water were restored to the crop
root zone by irrigation as the allowable water deple
tion level was decreased. Again, this occurred because
soil-water contents were always maintained near max
imum levels, and there was little available storage
space for rainfall.
Effective rainfall is that which is stored in the crop
root zone and available for use. In Fig. 9, effective rain
fall decreased with a decrease in allowable water deple
tion. It was also less for those management practices
which replenished all or most of the water deficit in
the crop root zone.
Fig. 7.Simulated number of irrigations as a function of al
lowable water depletion and application depth.
Fig. 8.Seasonal soil water requirements as a function of ir
rigation management practices.

32
Soil and Crop Science Society of Florida
Fig. 9.Effective rainfall as a function of irrigation manage-
ment practices.
Frequent, small applications increased effective
rainfall; however, the soil surface was wet frequently,
and nonproductive evaporation losses also increased.
Figure 10 shows the effects of the factors simulated on
evaporation losses. Because of the frequent, short dura
tion rainstorms common to the Gainesville area, there
was little effect of depth of application on seasonal
evaporation losses. There was a slight increase in
evaporation losses as very frequent irrigations were
scheduled for the allowable water depletions of only
1 %. In those cases the soil surface was almost con
tinuously wet from either irrigation or rainfall.
Irrigation requirements include soil-water require
ments, as well as evaporation, wind drift, and intercep
tion losses during sprinkler irrigation. Those com
ponents were simulated and summed to produce the
results given in Fig. 11. At large allowable water
depletions, irrigation requirements were considerably
greater when the entire soil profile was refilled at each
irrigation than when only a portion of the profile was
restored to field capacity. At lower allowable deple
tions, those differences were less significant. In general,
this occurrence depends upon the soil hydraulic prop
erties and rainfall distributions for the specific site.
In Fig. 11, the NWD treatment required the great
est total amount of water to be pumped, because rain
fall was not used effectively as previously discussed.
The 1-cm treatment required the second-greatest
depths of irrigation because evaporation and intercep
tion losses were great due to the frequent irrigations
and wet soil surface.
Irrigation water use efficiency can be expressed in
several ways. In Fig. 12, water use efficiency was ex
pressed as a percentage, and was calculated as a ratio
Fig. 10.Seasonal evaporation losses as influenced by irrigation
management practices.
Fig. 11.Seasonal irrigation requirements as a function of ir
rigation management practices.
WATER DEPLETION (%)
Fig. 12.Water use efficiency as influenced by allowable water
depletions and application depth.
of water requirements in the plant rooting zone to
rainfall plus water pumped. The best option was the
3-cm water application depth. Further use of this
simulation model would allow further refinement of
the depth of application, although it is apparent that
there is only little improvement to be made over the
range of values studied here. If the 10 years of weather
records are representative of long-term occurrences, it
is apparent that for the sandy soils (and, therefore,
limits on soil water depletion levels) and frequent rain
fall occurrences in the Gainesville area, water use
efficiency can be increased and irrigation requirements
decreased by allowing the soil to act as a reservoir to
increase effective rainfall. At irrigation depths of less
than NWD, irrigation requirements are insensitive to
depth of application.
The conclusions obtained from this study were
based on the criteria of irrigation applications and
water use efficiency only. An optimum irrigation man
agement strategy should be an economic decision, in
cluding such factors as labor costs for frequent small
irrigations versus those for less frequent, larger ones.
The results presented here do, however, provide the
framework for such economic decision model.
Additional research should be directed toward re
fining components of this model. Effects of water de
pletions upon yield reductions should be studied. In
this model it was assumed that irrigations occurred
instantaneously and that yield reductions did not

33
occur due to changes in soil-water content. The range
over which that assumption is valid should be inde
pendently evaluated. Also, the dynamics of soil-water
fluctuations should be included, especially as they in
fluence soil-water and evaporation losses.
SUMMARY AND CONCLUSIONS
A numerical simulation model was developed to
study the effect of various sprinkler irrigation manage
ment practices on crop water use efficiency. This model
allows the user to simulate the scheduling of irriga
tions for crop production. Model inputs required were
climatic, crop, and soil variables, specifically including
daily rainfall, pan evaporation, soil-water-capacity
function, effective rooting zone of the crop, and water
use coefficients versus time.
This model simulated a daily soil-water balance and
crop-water use, with the assumption that soil-water
contents did not decrease transpiration rates. In this
work, four levels of soil-water depletion and three
magnitudes of irrigation depths were studied using 10
years of daily rainfall records for Gainesville, Florida.
Seasonal irrigation requirements were found to de
crease with both greater allowable water depletions
and with smaller depths of application. This was due
to effective rainfall increasing with the same factors.
Seasonal evaporation losses were found to be un
affected by depth of applications and only mildly af
fected by decreases in allowable water depletions. This
was because evaporation rates remained fairly high due
to frequent rainstorms.
Seasonal irrigation requirements were found to be
less for an intermediate application depth, because
evaporation and interception losses were great for
small, frequent application, and because effective rain
fall was low for large, infrequent applications. The
optimum is specific for a given set of soil, crop, and
climatic conditions.
REFERENCES
1. Black, T. A., W. R. Gardner, and G. W. Thurtell. 1969. The
prediction o£ evaporation, drainage, and soil-water storage
for a bare soil. Soil Sci. Soc. Am. Proc. 33:655-660.
2. Burch, G. J., R. C. G. Smith, and W. K. Mason. 1978. Agro
nomic and physiological responses of soybean and sorghum
crops to water deficits. II. Crop evaporation, soil-water de
pletion, and root distribution. Aust. J. Plant Physiology 5:169-
177.
Christiansen, J. E., and J. R. Davis. 1967. Sprinkler irrigation
systems, p. 885-904. In R. M. Hagan, H. R. Haise, and T. W.
Edminster (Ed.). Irrigation of Agricultural Lands. Am. Soc.
Agron. Madison,Wis.
4. Kanemasu, E. T L. R. Stone, and W. L. Powers. 1976. Evapo-
transpiration model tested for soybean and sorghum. Agron.
J. 68:569-572.
5. Pair, C. H. 1969. Sprinkler Irrigation. Sprinkler Irrigation
Assn., Washington, D. C.
6. Priestly, C. H. B., and R. J. Taylor. 1972. On the assessment
of surface heat flux and evaporation using large-scale param
eters. Mon. Weather Review. 100:81-92.
7. Ritchie, J. T. 1972. Model for predicting evaporation from
a row crop with incomplete cover. Water Resour. Res. 8:1204-
1213.
8. Robertson, W. K., L. C. Hammond, J. T. Johnson, and G. M.
Prine. 1979. Root distributions of corn, soybeans, peanuts,
sorghum, and tobacco in fine sands. Soil Crop Sci. Soc. of
Florida Proc. 38:54-58.
9. SCS Engineering Division Stall. 1970. Irrigation Water Re
quirements. Technical Release 21, USDA. U. S. Government
Printing Office, Washington, D. C.
CORRECTION
The paper by T. L. Yuan, M. C. Lutrick, and W. K.
Robertson entitled Response of Soybeans and Oats to
Lime, Phosphorus, and Potassium on a Paleudult was
printed in error in the last issue of this Proceedings
(Soil and Crop Sci. Soc. Fla. Proc. 38: 116-121). Figures
3 and 4 are repetitions. Figure 4 should be as follows:
70 r
0 4.6 5.0 5.4 5.8 6.2 6.6 70 7.4
Soil pH
Fig. 4.Relationship between soil pH and oats yield in 1976.
Proceedings, Volume 39, 1980
3,

34
Soil and Crop Science Society of Florida
Soil-Water Characteristics of Histosols
as Related to Water Table Depth1
G. S. Rahi and S. F. Shih2
ABSTRACT
Soil water characteristics, imperative for designing
efficient water management systems, were studied in
subsiding organic soils (Histosols) in relation to dif
ferent water table depths. Soil samples were collected
at 5 to 15 and 15 to 30-crn depths from lysimeters where
water tables were maintained at 30, 60, and 90 cm
below the surface for about 3 years. A sugarcane
(Saccharum officinarum L.) crop was in its second
ratoon at the time of sampling. Results indicate that
water-yield coefficient values of the soil from the 60
and 90-crn water tables (WT) were 2 to 3 fold of those
obtained for soil from the 30-cm WT treatment. The
soil from the 15 to 30-cm depth in the 30-cm WT
treatment showed 5 to 10 times higher degree of re
sistance to initial wetting as compared with soil from
the 5 to 15-cm depth in the 30-cm WT and from the
5 to 30-cm depth in the 60 and 90-crn WT treatments.
The soil from the 15 to 30 cm depth in the 30-cm WT
combination also retained about 10 to 15% less water
at a given tension and released available water rela
tively faster than soil taken from other depths and
water table combinations at tensions higher than 4
bars. This layer of soil also appeared to possess 2 to 3
times lower saturated conductivity and capillary con
ductivity at a given degree of saturation as compared
with soil from the other sampling combinations.
Additional Index Words: Physical properties of
organic soils, Water yield coefficient, hydrophobic
nature of organic soils.
The study of soil water characteristics of organic
soil is very important for developing efficient water
management systems, especially in presence of high
water tables as recommended to reduce subsidence of
organic soils. High water tables not only require more
water for irrigation, but they also require more pump
ing for drainage after a heavy rainfall (Shih and
Gascho, 1980). However, the rate and amount of water
to be added or drained under specific conditions for
crop production largely depend on the water storage,
transmission, and release characteristics of the soil. All
of these properties are intimately related to the soil-
water characteristic of the soil.
A number of studies were reported in the literature
on the physical properties of organic soils in relation to
degree of humification and use of water-control sys
tems. Some of the related studies include those of
Boelter (1969, 1972) in Minnesota, Okruszko (1969)
in Poland, Korpijaakko and Radforth (1972) in Can
ada, Egglesmann (1972) in Germany, Pessi (1956) in
Finland, Clayton et al. (1942) and Weaver and Speir
(1960) in Florida, Boggie and Robertson (1972) in
^Florida Agricultural Experiment Station Journal Series No.
2314.
^Associate in Agricultural Engineering and Associate Professor
of Agricultural Engineering, respectively, University of Florida,
Agricultural Research and Education Center, Belle Glade, FL
33430.
Scotland, and Galvin (1972) in Ireland. Evaluation of
physical characteristics was also a significant com
ponent of many other studies conducted on muck soils
(Zelazny and Carlisle, 1974; Farnham and Finney,
1965; Feustel and Byers, 1930; and Hanrahan, 1954).
Most of these studies were conducted without any par
ticular relation to different water table depths. Lahde
(1972) studied seasonal variations in aerobic limits and
Pessi (1956) investigated thermal relations of organic
soils. Both of these studies were done in relation to
water table depths. The magnitude of subsidence and
microbial activity in relation to high water tables
were reported under subtropical conditions of south
Florida by many workers (Neller, 1944; Stephens, 1969;
Volk, 1972; and Tate, 1979). Unfortunately, not much
information is available on the concomitant physioco-
chemical changes induced by high water tables main
tained for long times. The main objective of this study
was to evaluate any variations induced by high water
table that might lie of consequence in designing ade
quate water management systems on organic soils.
MATERIALS AND METHODS
These studies were conducted under simulated
conditions in 1.2 m deep and 5.5 m diameter lysimeters.
Water table depths in these lysimeters were controlled
at 30, 60, and 90 cm below the soil surface in duplicate.
Organic soil was packed in the lysimeters to the bulk
density closely representing field conditions. Lysimeters
were installed 3 years prior to this study by Gascho and
Shih (1979) to evaluate the performance of sugarcane
(Saccharum officinarum L.) in relation to different
water table depths. A crop of sugarcane was in its
second ratoon when the soil samples were taken. Dis
turbed and undisturbed soil samples were taken from
5 to 15 and 15 to 30-cm depths in each lysimeter. Dif
ferent physical parameters monitored are described
below:
1. Water-Yield Coefficient: This coefficient meas
ured the amount of water released as the water table
receded in the soil. Undisturbed soil cores were taken
at two depths from four locations in each lysimeter.
The saturated core samples were subjected to 0.10 bar
pressure. Amount of water released between saturation
and 0.10 bar tension was used to represent the water-
yield coefficient (Boelter, 1969).
2. Rubbed and Unrubbed Fiber Percentage: These
percentages were used to indicate the degree of humifi
cation of peat. Undisturbed samples in cores were col
lected at two depths and four locations in each
lysimeter. Two samples from each depth were used to
determine the total oven dry mass (105 C). The other
two samples were analyzed for three main particle size
fractions, i.e., particles > 1 mm, in between 1 and 0.1
mm, and particles <0.1 mm in diameter according to
the method developed by Farnham and Finney (1965).
3. Water Drop Penetration Time Test: This test
was used to measure indirectly the degree of resistance
to wetting. The test actually measured the degree of
stability of hydrophobic nature of the soil.

35
Proceedings, Volume 39, 1980
This test and other subsequent physical property
determinations were conducted on disturbed soil sam
ples. Disturbed soil samples were taken to avoid any
interference from the roots and other extraneous
matter in evaluating the physical properties of organic
soil particles. Soil samples were collected from four
locations at two depths in each lysimeter. Soil was air
dried and passed through a 2-mm sieve.
Smooth surfaces were prepared in triplicate from
each sample and a medicine chopper was used to get a
uniform size water drop. The amount of time each
drop took to disappear was noted.
4. Saturated Hydraulic Conductivity: Saturated
conductivity was determined by packing air-dry soil to
the same bulk density in three layers in brass cores.
Measurements were made in triplicate by the standard
technique with constant water head (Klute, 1965).
5. Soil Water Retention and Release Relations: Soil
samples from each location were compacted to the same
density in small cores. The saturated samples were
subjected to tensions ranging from 1/3 to 15 bars in
the pressure chamber apparatus. Retention and release
of volumetric water content were studied as functions
of tension.
6. Available Water: Available range of water was
computed from the difference in the amounts of volu
metric water content retained at 1/3 bar and 15 bars.
This availability range was included to be studied as a
function of tension to see how the soil texture affected
water release in relation to degree of unsaturation at
a given density as far as availability of water to plants
was concerned.
7. Capillary Conductivity: Unsaturatecl hydraulic
conductivity was computed theoretically from the satu
rated hydraulic conductivity and soil water tension re
lations using the mathematical relationships of Camp
bell (1974). Capillary conductivity was determined to
study the empirical relation of decrease in hydraulic
conductivity on a relative basis with degrees of satura
tion over the available water range in the organic soils.
RESULTS AND DISCUSSION
Results obtained from various physical properties
were interpreted to establish any trend of change in
soil-water characteristics of organic soils in relation to
different water table depths. These studies were con
fined to the surface 30-cnr depth mainly for the reason
that predominant microbial activity was found to be
confined to the top few cm of soil (Tate, 1979). There
fore, any changes in the physical properties of the
medium were probably better reflected in the surface
soil as affected by its closeness to water table depth.
Data on water-yield coefficients are given in Table
1. These values, which vary on the average from 0.11 to
0.38 cm3/cm3, indicate that a larger volume of water
was released with receding water-table in the 90-cm
water table than any other water-table combination at
any depth. The least amount of water was released at
15 to 30-cm depth in the 30-cm water table treatment.
These water-yield coefficients were in the range of those
reported by Boelter (1974) for the moderately de
composed to well decomposed peat in Minnesota. One
probable reason for the lower water-yield coefficient in
the 30-cm water table depth was the lower amount of
water retained at both saturation and 1/10 bar tension,
TABLE 1.Water yield coefficients as related to water table
DEPTH.
Water table
depth
(cm)
Depth of
sampling
(cm)
Water yield coeff.
(cm31 cm3)
Rep I
Rep II
Avg.
90
5-15
.40
.36
.38
15-30
.34
.38
.34
60
5-15
.35
.29
.32
15-30
.24
.25
.24
30
5-15
.15
.16
.16
15-30
.14
.08
.11
which was due to an overall lower total porosity ob
served in this soil.
Proportions of rubbed and unrubbed fiber are
given in Table 2. Since the differences in the average
of determined values of various physical properties for
5 to 15 cm and 15 to 30-cm depths were small for the
60 and 90-cm water table depths, these values were
combined and their averages were used for making
interpretations. The values given in Table 2 in general
indicate that the proportion of rubbed and unrubbed
fibers for the 60-cm water table depth was quite close
to the proportion for the 90-cm depth. These values
were about 44 and 56%, respectively. However, two
replication averages did not give consistent results for
the 30-cm water table treatment, especially at the 15
to 30 cm sampling depth. The presence of secondary
and tertiary roots of sugarcane grown for the third
generation could be partly responsible for these in
consistencies in the soil layers above high water table.
Water drop penetration time results are given in
Table 3. These results indicate that the soil from the
15 to 30-cm depth of the 30-cm water table treatment
was the most resistant to wetting followed by the soil
zone above this hydrophobic layer. Degree of hy
drophobic nature of soil from the 90 and 60-cm water
table combinations were next in that order. However,
the problem was initial wetting; as the soil became wet
it behaved as other soil samples. Bond and Harris
(1964) observed that water repellency in soil was caused
by metabolic products of microorganisms. Though no
specific efforts were made to measure degree of swelling
on wetting, visual observations indicated that soil from
deep water table combinations swelled noticeably much
more than soil taken from a shallow water-table depth.
TABLE 2.Rubbed and unrubbed fiber analysis for different
WATER TABLE DEPTHS.
Water
table
depth
(cm)
Sampling
depth
(cm)
Rep
Prop, particle size frac.
(%)
> 1 mm
0.1-1 mm
0.1 mm
5-30
I
27.37
32.61
40.02
90
II
29.68
28.05
42.27
Avg
28.53
30.33
41.14
5-30
I
27.80
28.59
43.61
GO
II
24.93
31.76
44.31
Avg
26.06
30.18
43.96
5-15
I
17.31
31.11
51.58
30
II
20.52
33.63
45.85
Avg
18.92
32.37
48.72
15-30
I
23.22
42.76
34.02
30
II
17.30
31.80
50.90
Avg
20.26
37.28
42.46

36
Soil and Crop Science Society of Florida
Soil samples taken from the 15 to 30-cm depth in the
30-cm water-table depth plots did not show any
swelling effect. Disturbed soil samples gave empirical
relations without much reflection on the structural
arrangement of soil particles. However, these studies
did indicate the changes in the physical nature of
organic soil particles induced by water table depth.
Data on saturated hydraulic conductivity are also
given in Table 3. The data indicate that the conduc
tivity was maximum in the 90-cm water table depth
followed by the 60-cm water table. The saturated con
ductivity was the least in samples collected from 15
to 30-cm depth in the 30-cm water table treatment. The
lower conductivity in these shallow water table soil
samples could be due to smaller size of particles as is
also indicated by data given in Table 2. The decreased
conductivity of the soil layer above the shallow water
table (30-cm water table depth) could be due to a
gradual disappearance of hydrophobic character of soil
particles which then could have dispersed and clogged
the soil pores. These conductivity values were higher
by 10 fold than those reported by Weaver and Speir
(1960), Zelazny and Carlisle (1974), and Snyder et al.
(1978). The high values were obtained probably be
cause the disturbed soil samples were used and they
were not well packed.
Retention of volumetric water content at different
tensions between 1/3 and 15 bars is plotted in Fig. 1.
The general shape of the curves for all the soils and
the computed mathematical equations appear to be
similar to the typical soil water tension relations re
ported by Hillel (1971). Soil samples taken from the
60-cm water-table treatment retained more water than
samples taken from 90 and 30-cm water-table plots at
a given tension. However, there was not much differ
ence in amount of water retained in soil samples col
lected from different water table depth combinations
except in soil samples collected from 15 to 30 cm in
the 30-cm water table treatment at a given suction. Soil
from the zone above the shallow water table retained
about 0.05 to 0.10 cm3/cm3 less water at a given degree
of unsaturation over the available water range.
Percent available water was plotted as a function of
tension and is given in Fig. 2. The available volumetric
water content varied between 0.17 to 0.18 cm3/cm3 for
the 90 and 60-cm water-table treatments at 5 to 30-cm
depth and 30-cm water table treatment at 5 to 15-cm
depth. But, for the 30-cm water table treatment at 15
TABLE 3.Water drop penetration time test and hydraulic
CONDUCTIVITY VALUES FOR SOIL IN RELATION TO WATER TABLE DEPTH.
Water
table
depth
(cm)
Sampling
depth
(cm)
Rep
Water drop
penetration
time (sec)
Sat.
conductivity
cm/min
I
7.2
9.86
90
5-30
II
7.8
7.81
Avg
7.5
8.83
I
3.0
7.72
60
5-30
II
4.8
6.12
Avg
3.9
6.92
I
9.0
4.70
30
5-15
II
9.6
6.13
Avg
9.3
5.41
I
48.0
2.97
30
15-30
II
30.0
3.65
Avg
39.0
3.31
Fig. 1.Soil water tension relations as affected by water table
depth.
Fig. 2.Percent available water versus tension relations for
soil from different water table lysimeters.
to 30-cm depth this value was only 0.14 cm3/cm3. The
relationship in Fig. 2 indicates that there was no sig
nificant difference in the release of available water in
all combinations before 1-bar suction was approached.
About 35 to 40% of the available water was released as
the soil drained to 1 bar suction. At a suction of 8 bars
nearly 78 to 83% of available water was released in all
combinations except in soil from the 15 to 30-cm depth
of the 30-cm water table plots where as much as 94%
of available water was depleted. This indicated a rela
tive decrease in the physical activity of soil particles
caused by a decrease in surface adsorption forces. In
the wet range, it is the arrangement and particle size
that play a dominant role in soil water retention and
release whereas in the dry range water retention is
more a function of the soil particles surface properties.
Computed capillary conductivity values were plot
ted as a function of volumetric water content (Fig. 3).
The values in general indicate that capillary conduc
tivity decreased about 10 fold from saturation to field
capacity. Hydraulic conductivity could decrease from
100 to 1,000 times in this range for many soils as was
reported by Hillel (1971). The capillary conductivity
in the water content range of 0.45 and 0.20 cm3/cm3
decreased only 5 to 8 fold for all combinations except,
again, in the soil layer lying immediately above the
shallow water-table. The decrease in conductivity in

37
Proceedings, Volume 39, 1980
Fig. 3. Calculated capillary conductivity versus volumetric
water content relations.
this soil layer was only 3 fold. These water content
values corresponded to field capacity and 8-bar suc
tion, respectively. The unsaturated conductivity values
appeared to be quite high as compared with most soils.
From the results of these studies it can be concluded
that the three factors responsible for water release and
water retention in soils (i.e., the soil particle size, ar
rangement, and physicochemical nature which control
surface adsorption forces) were affected in organic soils
by the water table. This was indicated by the changes
observed in the physical constituents of the soil layer
above the shallow water table. A decrease in total
porosity, hydraulic conductivity, and physical water
adsorption activity, and an increase in hydrophobic
nature signified the presence of a soil zone that had less
capacity to hold an additional amount of water not
only because of its nearness to the water table but also
because of physical changes induced in the internal
make up of the soil. This could produce more run
off and more erosion and should be given due con
sideration in designing efficient water-management
systems on organic soils of the area. This means that a
water-management system designed to maintain a high
water table in organic soils should have adequate
drainage capability. This is important especially dur
ing a wet season to protect crop roots from standing
water for a long period of time.
LITERATURE CITED
1. Boelter, D. H. 1969. Physical properties of peats as related
to degree of decomposition. Soil Sci. Soc. Am. Proc. 33:606-
609.
2. Boelter, D. H. 1972. Preliminary results of water level control
on small plots in a peat bog. 4th Int. Peat Congr. (Otaniemi,
Finland) Proc. 3:347-354.
3. Boelter, D. H. 1974. The hydrologic characteristics of un
drained organic soils in the Lake States. In A. R. Aandahl,
S. W. Buol, D. E. Hall, and H. H. Bailey (ed.) Histosols
Their characteristics, classification, and use. SSSA Special
Pub. No. 6. Soil Sci. Soc. Am., Inc., Madison, Wis.
4. Boggie, R., and R. A. Robertson. 1972. Evaluation of horti
cultural peat in Britain. 4th Int. Peat Congr. (Otaniemi,
Finland) Proc. 3:185-192.
5. Bond, R. D., and J. R. Harris. 1964. The influence of micro-
flora on physical properties of soils. I. Effects associated with
filamentous algae and fungi. Aust. J. Soil Res. 2:111-122.
6. Campbell, G. S. 1974. A simple method for determining un
saturated conductivity from moisture retention data. Soil
Sci. 117:311-314.
7. Clayton, B. S., J. R. Neller, and R. V. Allison. 1942. Water
Control in the peat and muck soils of Florida Everglades.
Florida Agr. Exp. Sta. Bull. 378.
8. Egglesmann, R. 1972. The thermal constants of different
highbogs and sandy soils. 4th Int. Peat Congr. (Otaniemi,
Finland) Proc. 3:371-382.
9. Farnham, R. S., and H. R. Finney. 1965. Classification and
properties of organic soils. Adv. Agron. 17:115-162.
10. Feustel, I. C., and H. G. Byers. 1930. The physical and chem
ical characteristics of certain American peat profiles. USDA
Tech. Bull. 214.
11. Galvin, L. F. 1972. Reclamation of Irish peats for agricultural
development. 4th Int. Peat Congr. (Otaniemi, Finland) Proc.
3:425-434.
12. Gascho, G. J., and S. F. Shih. 1979. Varietal response of sugar
cane to water table depth, I. Lysimeter performance and
plant response. Soil and Crop Sci. Soc. of Florida Proc. 38:
23-27.
13. Hanrahan, E. T. 1954. An investigation of some physical
properties of peat. Geotech. 4:108-123.
14. Hillel, D. 1971. Soil and water,Physical Principles and
Process. Academic Press, New York.
15. Klute, A. 1965. Laboratory measurement of hydraulic con
ductivity of saturated soil. In C. A. Black (ed.) Methods of
Soil Analysis (Part I). Agronomy 9:253-261. Am. Soc. of
Agron., Madison, Wis.
16. Korpijaakko, M., and N. W. Radforth. 1972. Studies on
the hydraulic conductivity of peat. 4th Int. Peat Congr.
(Otaniemi, Finland) Proc. 3:323-334.
17. Lahde, E. 1972. Seasonal variations in the depth of aerobic
limit and the ground water table in virgin and in drained
Myrtillus spruce swamp. 4th Int. Peat Congr. (Otaniemi,
Finland) Proc. 3:355-370.
18. Neller, J. R. 1944. Oxidation loss of low moor peat in fields
with different water tables. Soil Sci. 58:195-204.
19. Okruszko, H. 1969. Muck soils of valley peat bogs and their
chemical and physical properties. Translated from Polish by
USDA, Roczn. Nauk. Roln. 74:5-89.
20. Pessi, Y. 1956. Studies on the effect of the admixture of
mineral soil upon the thermal conditions of cultivated peat
land. State. Agr. Res. Pub. of Finland No. 147, Helsinki,
Finland.
21. Shih, S. F., and G. J. Gascho. 1980. Water requirements for
sugarcane production. Transactions of the Am. Soc. of Agre.
Eng. (in press)
22. Snyder, G. H S. F. Shih, and D. L. Myhre. 1977. Character
istics of inplace and potential soil fill materials as related to
water leaching at the surfside landfill in Dade County. Final
Report on Town of Surfside Landfill Closing Study, Airan
Environmental Consultants, Inc., Coral Gables, Fla.
23. Stephens, J. C. 1969. Peat and muck drainage problems. J. of
Irrig. and Drainage Division. Am. Soc. Civil Eng. 95(IR2):
285-305.
24. Tate, R. L. 1979. Microbial activity in organic soils affected
by soil depth and crop. Applied and Environ. Microbiol. 37:
1085-1090.
25. Volk, B. G. 1972. Everglades histosol subsidence. I. C02
evolution as affected by soil type, temperature, and moisture.
Soil Crop Sci. Soc. Florida Proc. 32:132-135.
26. Weaver, H. A., and W. H. Speir. 1960. Applying basic soil
water data to water control problems in Everglades peaty
muck. USDA. ARS Bull. 40-41.
27. Zelazny, L. W., and V. W. Carlisle. 1974. Physical, chemical,
elemental, and oxygen-containing functional group analysis
of selected Florida Histosols. In A. R. Aandahl et al. (ed.)
Histosols. Their characteristics, classification, and use. SSSA
Special Pub. No. 6. Soil Sci. Soc. of America, Inc., Madison,
Wis.

38
Soil and Crop Science Society of Florida
Major Land Resource Areas in Florida
R. E. Caldwell1
ABSTRACT
Three categories of land resource maps used in the
United States are introduced and briefly defined. They
are land resource regions, major land resource areas,
and land resource units. Greater emphasis is given to
major land resource areas (MLRAs) as they comprise
the groupings being considered for a new general soil
map of Florida presently in preparation. Two earlier
MLRA maps by the USDA Soil Conservation Service,
one in 1973 and the other in 1978, are presented and
discussed as to their suitabilities. Finally, a revised
MLRA map is proposed for consideration as constitut
ing the Major Land Resource Areas of Florida upon
which the new general soil map of the State should be
based.
Additional Index Words: Land resource maps,
MLRAs, General soil map of Florida, Soil taxonomy,
Soil survey.
It is often quite important to assemble and organize
currently available information concerning land as a
resource for a wide variety of uses, including agricul
tural, industrial, recreational, engineering, and others.
Such information can best be presented in the form of
a map and a report, either of which can be revised as
improved technology provides new information.
In the preparation of land resource maps at nat
ional and state levels, three categories have evolved:
(a) land resource regions, (b) major land resource
areas, and (c) land resource units (1). Land resource
regions consist of geographically associated major land
resource areas and are most significant for land-use
planning on a national scale. Major land resource
areas are defined as consisting of geographically asso
ciated land resource units and are most important in
land-use planning on a state-wide level, although such
areas also have value in inter-state, regional, and
national planning. Land resource units consist of
geographic areas of land that are characterized by
particular patterns of soil and climate. A unit may
occur as a single continuous area or as several separate
but nearby areas which usually comprise several
thousand acres in extent. Many such units are also
known as soil associations. It is readily apparent, there
fore, that uniformity is greatest in land resource units,
considerably less in major land resource areas, and very
much less in land resource regions. It is also clear that
somewhat similar units may be grouped into a single
area, and similar areas (in turn) are often grouped to
gether within a single region.
This paper is primarily concerned with the dis
tribution and extent of various major land resource
areas (MLRAs) in Florida as designated in the past
and also with suggested changes which more ade
quately describe each of the MLRAs and show their
extent and distribution within the State.
iProfessor (Genesis and Classification), Soil Science Depart
ment, Florida Agricultural Experiment Station, Gainesville, FL
32611.
HISTORY
A general soil map of Florida (5) was published in
1962 which grouped dominant soils into associations
based primarily on drainage and kind of parent ma
terials from which they were developed. A bulletin was
later published as a supplement to this map which
described each of the mapping units (4).
With increased knowledge in regard to soil genesis,
morphology, and classification, a new system of soil
classification was adopted for use in the United States
on 1 January 1965. The development of this classifica
tion scheme began in 1951 and underwent a series of
revisions or approximations before it was finally pub
lished as Soil Taxonomy (6) in 1975. This new system
treats soil as individual three-dimensional entities
which can be grouped together according to their
physical, chemical, and mineralogical characteristics
(2). Soil taxonomy now requires improved soil profile
descriptions to greater depths in the field supple
mented with specialized laboratory data. This has re
sulted in more precise definitions of most older soil
series and recognition of many new series. For example,
some of the soils in the earlier concept of the Lakeland
soil are now included in 11 other soil series, several of
which are completely new.
It is, therefore, necessary that a revised general soil
map of Florida be published based on present soil
taxonomy, especially since the previous map and report
on Florida soils are out-of-date and out-of-print. Prog
ress is being made toward this project by personnel of
the Florida Agricultural Experiment Stations in co
operation with the USDA Soil Conservation Service.
MLRA MAPS OF FLORIDA
During the early planning of this revised general
soil map, it was decided to group the various soil asso
ciations into MLRAs (each of which would be dis
tinguished from one another on the State map by its
own color) for ease of presentation and understanding.
Accordingly, a study was made of various MLRA
maps of the State of Florida.
One of these (Fig. 1) by the USDA-SCS in 1973 is
a slightly revised version of a small MLRA map shown
in the upper right-hand corner of the previous general
soil map of Florida (5). While the Southern Coastal
Plain and the Atlantic Coast Flatwoods properly
match up with the adjoining MLRAs in Alabama and
Georgia, several other judgments make this map un
suitable. These are: (a) the South Central Florida
Riclge extends too far to the north (almost as far as
the North-Central Florida Ridge), (b) the Southern
Florida Flatwoods extend up into Duval County
which is certainly not part of South Florida, (c) the
Atlantic Coast Flatwoods end in Duval County, but
the Atlantic Coast certainly extends all the way down
the eastern coast of Florida, and (d) the Gulf Coast
Flatwoods end near the southern Pasco County
border, but the Gulf Coast definitely extends much
farther south along the western coast of the State.
Perhaps recognizing that changes can be made in
MLRA boundaries, the Soil Conservation Service

Proceedings, Volume 39, 1980
39
HU Southern Coastal Plain
f 1 North-Central Florida Ridge
- South-Central Florida Ridge
_ Atlantic Coast Flatwoods
- Eastern Gulf Coast Flatwoods
Southern Florida Flatvjoods
Southern Florida Lowlands
Florida Everglades & Associated Areas
Fig. 1.Major land resource areas (SCS 1973).
(SCS) shows these revisions as occurring in the State
as of September 1978 (Fig. 2). Here again, the South
ern Coastal Plain and the Atlantic Coast Flatwoods
match up well with the MLRAs in Alabama and
Georgia, but other faults and misnomers still exist to
make this MLRA map unsuitable. They are: (a)
the South-Central Florida Ridge extends up into
Alachua and Clay Counties, which are certainly not
considered to be part of South Florida, (b) the South
ern Florida Flatwoods still extend up into Duval
County with a small area shown in Alachua County,
both of which are much too far north of areas con
sidered to be Southern Florida, (c) the Atlantic
Coast Flatwoods still end in Duval County, but the
Atlantic Coast certainly extends all the way down the
eastern coast of Florida and, (cl) the Gulf Coast Flat-
woods end at the southern boundary of Levy County,
but the Gulf Coast definitely has flatwood areas farther
south along the western coast of the State.
If MLRAs are indeed to be the broad groupings
upon which the new general soil map of Florida is to
be based, it is evident that still more revisions in their
boundaries and nomenclature are needed in order to
overcome the objections detailed above. The map
shown in Fig. 3 was prepared from land area informa
tion contained in the Florida General Soils Atlas (3),
and the names of MLRAs were also changed to better
describe the areas involved.
A study of this MLRA map of Florida reveals those
changes made to include the following: (a) the South
ern Coastal Plain and the Atlantic Coast Flatwood
still match-up with the MLRAs in Alabama and
Georgia; however, some changes have been incorpo
rated in their southern in-State boundaries due to im
proved current knowledge, (b) the Central Florida
Ridge includes those areas formerly listed as North-
Central and South-Central Florida Ridge, with
relatively minor changes in boundaries, (c) the South
ern Florida Flatwoods has its northern boundary
moved southward from Duval County to the areas
including Orange and Brevard Counties, (d) the
Atlantic Coast Flatwoods and the Gulf Coast Flat-
Fig. 2.Major land resource areas (SCS 1978).
Fig. 3.Major land resource areas (Proposed).
woods now extend along the Atlantic and Gulf
coasts, respectively, in a southerly direction until they
border a different MLRA, and (e) the Everglades and
Associated Areas are connected (thus differing from
Fig. 1 and also include the Southern Florida Low
land shown in Fig. 2).
It is proposed that this map (Fig. 3) be accepted
by state and federal agencies, with perhaps only
slight modifications if necessary, as the Major Land
Resource Areas of Florida. To permit the use of
these MLRA designations on the general soil map to
be published at a scale of 1:1,000,000, an additional
map unit entitled Miscellaneous Land Types would
most probably be needed. It would include such areas
as coastal beaches and dunes, saltwater marshes and
swamps, and certain alluvial lands bordering the larger
rivers such as the Escambia, Apalachicola, and

40
Soil and Crop Science Society of Florida
Ochlockonee. Due to the scale of the maps in this
paper, this last proposed MLRA could not be shown.
LITERATURE CITED
1. Austin, M. E. 1965. Land resource regions and major land
resource areas. USDA Handbook No. 296. Washington, D.C.
82 p.
2. Caldwell, R. E. 1978. Soil taxonomy; a new improved system
of soil classification, p. 22-33. In Soil Identification Handbook.
Univ. Florida Soil Science Publ., Gainesville, Fla.
3. Florida Division of State Planning. 1974. The Florida general
soil atlas: with interpretations for regional planning districts
I through X, (set of 5). State of Florida, Tallahassee, Fla.
4. Smith, F. B., R. G. Leighty, R. E. Caldwell, V. W. Carlisle,
L. G. Thompson, Jr., and T. C. Mathews. 1967. Principal soil
areas of Florida, a supplement to the general soil map. Univ.
Florida Agrie. Exp. Sin. Bui. 717. Gainesville, Fla.
5. Soil Survey Staff. 1962. General soil map of Florida. Univ.
Florida Agrie. Exp. Stn. Publ. in coop. USDA Soil Consen'.
Serv., Gainesville, Fla.
6. Soil Survey Staff. 1975. Soil taxonomy; a basic system of soil
classification for making and interpreting soil surveys. USDA-
SCS Agrie. Handbook No. 436. U.S. Government Printing
Office, Washington, D.C.
Sulfur Fertilization of Com Seedlings1
C. C. Mitchell, Jr. and R. N. Gallaher2
ABSTRACT
Lack of sulfur (S) in many fertilizer materials used
on crops under intensive multiple cropping may cause
plant nutrient imbalances that reduce yield. The
purpose of this experiment was to determine the need
for S on two cultivars of corn (Zea mays L.), to evalu
ate different sources of S, and to determine the most
effective method of application of S to corn seedlings.
A N:S imbalance was observed in emerging corn seed
lings in the spring of 1979. This imbalance may have
been caused by high fertilizer rates and intensive man
agement with no S applied to a multiple-cropping,
minimum-tillage experiment on an Arredondo fine
sand (loamy, silicious, hyperthermic Grossarenic
Paleudult) in north-central Florida. Two rates of foliar-
applied magnesium sulfate and potassium sulfate (5
and 10 kg/ha S) and one rate of agricultural-grade
magnesium sulfate, potassium sulfate, and calcium sul
fate (10 kg/ha S) were applied to 30-day-old plants of
a short-season corn grain variety and a full-season corn
forage variety.
All of the S treatments increased the S concentra
tion in mature leaves of 55-day-old plants and in the
total plant of the full-season forage variety at harvest.
However, neither grain nor forage yield or quality was
influenced by the S treatments. All plants had grown
out of the S-deficient condition at 55 days. They were
marginally Mg deficient 21 days after emergence. As
the plants grew out of the S deficiency, Mg became the
most limiting nutrient. The short-season variety gave
a positive yield response to Mg in both the foliar spray
and in the agricultural-grade material. The full-season
variety did not respond to the Mg treatments but
yielded 37 % more grain than the short-season variety.
Additional Index Words: Mg response on corn,
Multicropping fertilization.
The sandy soils of north Florida are low in avail
able sulfur (S). Neller (1959) found that the extract-
iFlorida Agricultural Experiment Stations Tournal Series Num
ber 2220.
^Graduate Assistant, Soil Science Department, and Associate
Professor of Agronomy, Agronomy Department, Institute of
Food and Agricultural Sciences, University of Florida, Gaines
ville, FL 32611.
able sulfate-S concentration of the surface horizons of
some Florida soils ranged from 0 to 4.5 ppm, and clover
responded to applications of S in all areas of the state
(Neller et ah, 1951; Neller, 1952). Deep-rooted plants
are able to utilize adsorbed sulfate associated with the
clay in lower soil horizons, but seedlings may exhibit
S-deficiency symptoms when grown on sandy surface
soils with no S fertilization (Neller, 1959; Ensminger,
1954). With intensive management, S-free fertilizers,
and little S available to crops through the atmosphere,
rainfall, or irrigation, S deficiencies are likely to be
come more widespread for crops grown on Florida soils.
Interest in multiple cropping and minimum tillage
as intensive management practices is increasing
throughout Florida. Multicropping practices require
careful soil fertility management since the several crops
removed in a season require more nutrients than the
single crop ordinarily planted. Corn planted in 1979
in an established, multiple cropping, minimum tillage
experiment emerged with symptoms of S deficiency.
Several commercial corn crops in north-central Florida
were also observed witli symptoms indicating S and/or
Mg deficiencies early in the season. The objective of
the study reported here was to evaluate different
S-containing chemicals as fertilizers for correcting the
S deficiency symptoms observed in the seedling corn.
MATERIALS AND METHODS
In 1977, a multiple cropping, minimum tillage ex
periment was begun at the Green Acres Agronomy
Farm in north-central Florida on an Arredondo fine
sand (loamy, silicious, hyperthermic Grossarenic
Paleudult). One phase of this experiment involved the
following cropping system.
1. Wheat (Triticum aestivum L. Holley) was
planted in late fall and harvested as forage in
early spring.
2. Two corn (Zea mays L.) hybrids were planted in
early spring in the wheat stubble, (a) The short-
season hybrid (Dekalb XL-12) was harvested in
mid-summer for grain (corn grain system), (b)
The full-season hybrid (Dekalb XL-395A) was
harvested for forage at the same time (corn
forage system).
3. Forage sorghum (Sorghum bicolor L. Dekalb
FS24), millet (Pennisetum americanum L.

41
Proceedings, Volume 39, 1980
Gahi 3) or a sorghum x sudangrass hybrid
(Sorghum sudanense (Piper) Stapf Dekalb
SX16) was planted after the corn and harvested
for forage in the fall.
From the spring of 1977 to the spring of 1979, seven
crops were grown and harvested on the experimental
site. High rates of N, P, and K and clolomitic limestone
were applied to produce the crops, but no S was ap
plied.
In the spring of 1979, corn seedlings of both the
short-season (85-90 day) grain variety and the full-
season (120-125 day) forage variety emerged with
S-deficiency symptoms. Analysis of samples of the 21-
clay-old seedlings verified the symptoms as a N:S im
balance.
The corn plots of the multicropping experiment
were subdivided into a split-plot experiment with two
corn varieties as the main plots. Eight S treatments
were applied as either foliar sprays or agricultural-
grade material (Table 1). Treatments were replicated
five times. The foliar sprays were applied in two ap
plications, 10 days apart, beginning when the plants
were 30 days old. All of the agricultural grade ma
terials were applied when the plants were 30 days old.
Leaf samples were taken from the uppermost, ma
ture leaves 14 days after the final foliar fertilization
(pretassel stage for Dekalb XL 12). Leaf samples were
dried at 70 C in a forced-air oven, ground to pass a
1-mm screen, ashed, and analyzed for P, K, Ca, Mg, Zn,
Cu, and Mn. Nitrogen was determined by an auto
mated procedure with a Technicon AutoAnalyzer. A
100-mg sample of the dry, ground tissue was placed
into a 75-ml pyrex test tube. These samples were di
gested in a mixture of 10 ml concentrated H,S04, 2 ml
of H202, and 3.2 g of a salt-catalyst mixture (90%
KS04: 10% CuS04) with three boiling chips for 2.5
hours on an aluminum block heated to 385 C. The
digested liquid was then diluted to 75 ml with distilled
water and analyzed for N. Sulfur was measured by a
turbidometric method after pre-digestion with a Mg
TABLE 1.Sources, rates, and methods of application of S.
Source
S ratef
Method
-kg/ha-
Magnesium sulfate
(MgS04.7H20)
5
Foliar spray
Magnesium sulfate
(MgS04.7H20)
10
n n
Potassium sulfate
(K2so4)
5
n //
Potassium sulfate
(k2so4)
10
n n
Magnesium sulfate
(Agricultural grade)
10
Soil applied
Potassium sulfate
(Agricultural grade)
10
// n
Calcium sulfate
(Agricultural grade)
10
// n
Check
0

fFoliar sprays were applied to 30-day old seedlings in two
applications, 10 days apart. Agricultural grade material was ap
plied to soil in one application.
(N03)2/HN03 solution and ashing in a muffle furnace
(Massoumi and Cornfield, 1963; Chaudry and Corn
field, 1966). The residue was dissolved in 0.1N HC1.
For analyses of the other nutrients, 1 g of plant tissue
was ashed in a muffle furnace, dissolved in 0.1N HC1
and brought to 100 ml volume. Phosphorus concentra
tion was measured with a Technicon Auto-Analyzer.
Potassium was determined by flame emission, and the
other cations were determined by atomic absorption
spectrophotometry.
Dekalb XL-12 was harvested for grain 122 days after
planting. At the same time, Dekalb XL-395A was har
vested for forage by removing the above-ground por
tion of the plant. Whole-plant samples were taken from
the forage corn. Grain samples were taken from both
varieties.
The soil was sampled from an area adjacent to the
experiment. Samples were collected from four depths,
0 to 15 cm, 15 to 30 cm, 30 to 60 cm, and 60 to 80 cm.
Samples were screened and air dried. Extractable
S04-S was determined by extracting the soil with a
0.01A4 Ca(H2PO,)2. H20 solution and determining S
turbidometrically (Ensminger, 1954; Fox et ah, 1964).
RESULTS
Analyses of the 21-day-old seedlings are reported in
Table 2. These plants were definitely low in S with an
average S concentration of 0.12%. The critical con
centration of S in young corn plants has been reported
to be around 0.20% (Fox et ah, 1964; Stewart and
Porter, 1969; Jones and Eck, 1973; Terman et al.,
1973). The N:S ratios of 39 and 42 for the two cultivars
were larger than the optimum of 16 for plant protein
(Terman et ah, 1973). The seven harvested crops in the
corn grain system and the corn forage system removed
an estimated 48 and 63 kg/ha S, respectively, during
the two previous years (Table 3). No fertilizer S was
applied during this time. Removal of N,P,K, and Mg
in the harvested portion of the crop was calculated to
be in balance with that applied.
Applied S from non-Mg sources had no significant
effect on the final grain yield of either variety of corn
(Table 4). The full-season variety (Dekalb XL395A)
yielded 37% more than the short-season variety. This
may be attributed to the fact that the long-season corn
had a longer growing period in which to recover from
the initial stunting due to the severe S deficiency. The
short-season variety never fully recovered and prob
ably was unable to develop an extensive root system
before flowering.
TABLE 2.Mineral concentration of 21-day-old corn seed-
LINGS.f
N
S
P
K
Ca
Mg
N/S
%
Dekalb XL12
(grain)
4.62
0.117
0.83
3.39
0.42
0.19
39
Dekalb XL39SA
(forage)
5.04
0.121
0.87
3.15
0.39
0.20
42
Critical
levelsj
3.5
0.20
0.40
3.0
0.20
0.20
16
f All values are the means of five replications.
JFox et al., 1964; Stewart and Porter, 1969; Jones and Eck.
1973; Terman et al., 1973.

42
Soil and Crop Science Society of Florida
TABLE 3.Nutrients applied and removed from the soil by two cropping systems over a 2-year
PERIOD.
Crop
Dry
Nutrients applied matter
Year N P K Mgt harvested
Nutrients removed
P K Mg SJ
kg/ha
Corn grain system
Wheat forage
1977
111
18
84
385
2,985
63
11
58
4
3
Corn grain
//
188
34
297
0
3,620
66
14
14
4
4
Summer forage
rr
113
0
0
0
7,530
105
22
177
20
15
Wheat forage
Corn grain
1978
111
18
84
0
2,504
59
10
63
4
3
rr
188
34
297
0
5,870
86
19
29
6
6
Summer forage
rr
113
0
0
0
6,844
79
16
151
17
14
Wheat forage
1979
111
18
84
0
3,124
91
13
60
4
3
TOTAL
935
122
846
385
32,474
Corn forage system
549
105
552
59
48
Wheat forage
1977
111
18
84
385
2,930
63
11
61
3
3
Corn forage
tt
188
34
297
0
23,940
268
53
306
36
19
Summer forage
//
113
0
0
0
6,269
122
19
137
19
13
Wheat forage
1978
111
18
84
0
2,334
57
12
67
4
2
Corn forage
//
188
34
297
0
12,940
131
27
107
21
10
Summer forage
rr
113
0
0
0
6,255
72
16
126
17
13
Wheat forage
1979
111
18
84
0
3,048
86
12
66
4
3
TOTAL
935
122
846
385
57,716
799
150
870
104
63
fMg from 4.5 metric tons/ha of dolomitic limestone containing 30% MgCOs.
fS removal estimated from tissue analyses from 1979 samples and from values reported in the literature.
TABLE 4.Leaf and grain analyses and yields of two corn cultivars as affected by rates of
FOLIAR APPLIED S.
s
rate
Leaf analysis at 55 days
Mg:cation
S* N Mg Ca ratio
Grain analysis at harvest
Mgrcation Yield
S N Mg Ca ratio Grain Forage
% %
Dekalb XL-12 (short-season)
0
0.17c*
2.67
0.10
0.25
0.11
0.11
1.65
0.12
.004
0.49
5
0.21b
2.50
0.12
0.23
0.12
0.11
1.71
0.12
.002
0.48
10
0.25a
2.48
0.12
0.23
0.12
0.10
1.74
0.12
.003
0.48
quintal/ha
26a
30a
29a
Dekalb XL-395A (full-season)
0
0.18c
2.47
0.09
0.18
0.10
0.11
1.44
0.11
.003
0.50
48ab
96a
5
0.22b
2.53
0.11
0.19
0.11
0.11
1.43
0.12
.002
0.50
45ab
102a
10
0.26a
2.69
0.11
0.19
0.12
0.11
1.46
0.11
.002
0.50
52a
100a
Means followed by the same letter are not significantly different by Duncans multiple range test at the 0.05 level within each variety.
The MgSO.j.7 FLO foliar sprays and the agricultural
grade MgS04 significantly increased grain yield of the
short-season variety at the 5% level of probability over
the other treatments (Fig. 1). These results warranted
a closer look at the Mg status of the plants. The tissue
analysis of the 21-day old seedlings indicated a Mg
concentration of 0.19% in the short-season variety
(Table 2). While this level is marginal in seedling
corn (Jones, J. B., 1974), it did not concern us as much
as the N and S imbalance. Dolomitic limestone had
been applied to all plots the previous year at the rate
of 4.5 metric tons/ha (approximately 385 kg/ha Mg).
By the time the plants were 55 days old, S concentra
tion had increased in the leaves of plants from the
check plots to 0.17 and 0.18%, which is considered to
be above the critical level for plants of this age (Tables
4 and 5). All of the S treatments increased the S con
centration of the tissue significantly over that of the
check, but did not affect yield of grain or forage. The
N:S ratio had decreased to an average of 11 for the
treated plots and 16 for the check plots. These values
were within the optimum range, indicating an ade
cnate ratio of N and S in the plant tissue. This was
observed in each variety. Flowever, the Mg concentra
tion of the tissue continued to decrease below a critical
level in all treatments. The MgS04.7 FLO foliar sprays
tended to increase the Mg concentration of the tissue,
but these differences were not significant at the 5%
level of probability (Table 5). The significant increase
in yield of the Mg-treated plots of the short-season
variety could have had a dilution effect on the Mg
concentration in the tissue. The same trend in Mg con
centration was observed in the whole-plant samples
of the full-season forage variety (Table 5). However,
neither grain nor total forage yield of the full-season
variety was influenced by any of the treatments. The
depressed yield of Dekalb XL395A by the soil-applied
MgSOj cannot be explained by any of the treatment
variables.
The Mg: total cation ratio in the plant tissue was

43
Proceedings, Volume 39, 1980
Dekalb XL-12 Dekalb XL-395A
Fig. 1.Effect of MgS04 treatments on grain and forage yields
of two co' n cultivars.
calculated, but these values, like Mg, were not very
closely correlated with yield (Tables 4, 5, and 6). The
N:S ratios in whole-plant samples of the forage corn
at harvest were different in samples from treated plots
(ratio=16) and check plots (ratio=18). However, all
values were close enough to the optimum that no sig
nificant differences in yield or quality of the forage
would be expected.
TABLE 6.Mineral analysis of forace at harvest (122 days)
of Dekale XL395A as affected by source and method of appli
cation.
Forage analysis at harvest
Source
Method of
application
S
N
Mg
Ca
Mg:cation
ratio
MgS04.7H,0
foliar
0.08
1.19
0.14
%
0.14
0.28
//
soil
0.08
1.20
0.12
0.15
0.22
k,so4
foliar
0.08
1.22
0.12
0.13
0.26
//
soil
0.08
1.11
0.13
0.13
0.30
CaS04.2H.,0
soil
0.07
1.21
0.13
0.14
0.25
Check

0.07
1.26
0.12
0.13
0.25
Because S is an essential component of plant pro
tein, and protein is one of the important properties
contributing to the quality of forage and grain (Tis
dale, 1977), mineral concentrations of the grain sam
ples were studied (Tables 4 and 5) to evaluate the
effect of S treatments on grain quality. There were no
significant treatment effects on the S, N, or Mg con
centration of the grain samples and no differences in
the N:S ratios or Mg:total cation ratios.
DISCUSSION
Intensive cropping of these plots during 2 years
removed large quantities of nutrients from the soil.
The forage corn system removed 799, 150, 870, and
104 kg/ha of N, P, K, and Mg, respectively, from the
soil over the 2-year period. Dining this same period,
935, 122, 846, and 385 kg/ha of N, P, K, and Mg were
applied (Table 1). No S had been applied to the soil,
but an estimated 63 kg/ha of S was removed in the
forage-corn system. The grain corn system removed
approximately 48 kg/ha S. Since most of the above
ground portion of all crops was removed from the
plots, there was no opportunity for S to be returned to
the soil surface as organic matter. Consequently, S was
TABLE 5.Effect of S source and method of application on yield and leaf and grain analyses
OF TWO CORN CULTIVARS.
Source
Method of
application
Leaf analysis at 55 days
Grain analysis at harvest
Yield
S
N
Mg
Ca
Mgrcation
ratio
S
N
Mg
Ca
Mg:cation
ratio
Grain
Forage
- %
- %
quintal/ha ....
Dekalb XL-12 (short-season)
MgS04.7H.,0
foliar
0.23
2.58
0.13
0.24
0.12
0.10
1.71
0.12
.003
0.48
34a*

//
soil
0.23
2.59
0.10
0.23
0.12
0.11
1.73
0.12
.001
0.47
32a

K..SCL
foliar
0.23
2.40
0.11
0.23
0.12
0.10
1.74
0.12
.002
0.48
24 c

rr
soil
0.24
2.50
0.11
0.24
0.12
0.11
1.70
0.12
.002
0.47
26 be

CaS04.2Ho0
soil
0.24
2.61
0.12
0.24
0.12
0.11
1.69
0.12
.002
0.55
27 be

Check
0.17
2.67
0.10
0.25
0.11
0.11
1.65
0.12
.004
0.49
26 be

Dekalb XL-395A (full-season)
MgS04.7H,0
foliar
0.25
2.56
0.11
0.19
0.12
0.11
1.44
0.12
.001
0.50
49ab
97ab
//
soil
0.22
2.30
0.10
0.20
0.10
0.11
1.55
0.12
.001
0.50
35 b
79 b
k2so4
foliar
0.25
2.65
0.11
0.19
0.11
0.11
1.46
0.12
.002
0.50
48ab
106ab
//
soil
0.23
2.46
0.11
0.21
0.11
0.10
1.47
0.11
.002
0.49
46ab
99ab
CaS0l.2H0
soil
0.26
2.56
0.09
0.20
0.10
0.11
1.51
0.12
.005
0.51
46ab
08ab
Check
0.18
2.47
0.09
0.18
0.10
0.11
1.44
0.11
.003
0.50
47ab
96ab
*Means within varieties followed by the same letter are not significantly different at the 0.05 level by Duncans multiple range test.

44
Soil and Crop Science Society of Florida
depleted from the surface horizons. The preceding
wheat crop had immobilized any available S during
the fall and winter months, and there had been no
opportunity for microorganisms to mineralize soil or
ganic S and the S immobilized in the wheat stubble.
An insufficient amount of soil S was available to the
emerging corn seedlings in the early spring. High rates
of fertilizer N prior to planting antagonized the N:S
imbalance in the young plants. Magnesium uptake was
probably reduced by the high K rates applied prior to
planting. Double-acid extractable Mg averaged 25 ppm
in the upper 30 cm of soil in the experimental area.
All plants were able to grow out of the S-deficient
condition as the roots reached adsorbed S associated
with the argillic horizon in this soil. Soil analyses indi
cated increasing extractable sulfate-S with depth in the
horizon.
0 -15cm (Ap horizon) 2.2 ppm S
15-30cm (A21 horizon) 2.8 ppm S
30-60cm (A22 horizon) 3.5 ppm S
60-80cm (Bt horizon) 16.4 ppm S
Increased mineralization of organic S later in the
season probably also contributed to the improved S
nutrition in the plants.
CONCLUSIONS
Neither foliar sprays of S as potassium sulfate nor
soil-applied S as potassium sulfate or gypsum at 10
kg/ha had any effect on grain or forage yield of Dekalb
XL-12 or Dekalb XL-395A hybrid corn. All S treat
ments increased the S concentration and improved the
N:S: ratio of mature leaves at 55 days in both corn
varieties and in the total plant of the Dekalb XL395A
at harvest. Sulfur treatments had no effect on the
quality or mineral analysis of grain samples of either
variety.
All plants were marginally Mg deficient 21 days
after emergence. As the plants grew out of a S-deficient
condition, Mg became the most limiting nutrient. The
short-season variety (Dekalb XL 12) responded to Mg
in both the foliar spray and in the agricultural-grade
material with increased grain yield. The full-season
variety did not respond to the Mg treatments. This
variable response may be explained by the fact that the
full-season variety was able to utilize more soil Mg and
had a longer period in which to recover from the
stunting of the early-season deficiencies.
LITERATURE CITED
Chaudry, I. A., and A. H. Cornfield. 1966. The determination of
total sulfur in soil and plant material. Analyst 91:528-530.
Ensminger, L. E. 1954. Some factors affecting the adsorption of
sulfate by Alabama soils. Soil Sci. Soc. Am. Proc. 18:259-264.
Fox, R. L., H. M. Atesalp, D. H. Kampbell, and H. F. Rhoades.
1964. Factors influencing the availability of sulfur fertilizers
to alfalfa and corn. Soil Sci. Soc. Am. Proc. 28:406-408.
Jones, J. 15. 1974. Plant analysis handbook for Georgia. Coop.
Ext. Ser. Bul. no. 735. University of Georgia, Athens, Georgia.
Jones, J. B and H. V. Eck. 1973. Plant analysis as an aid in
fertilizing corn and grain sorghum. In L. M. Walsh and J. D.
Beaton (ed.). Soil testing and plant analysis. Soil Sci. Soc.
Am., Madison, Wis.
Jordan, H. V. 1964. Sulfur as a plant nutrient in the southern
United States. Tech. bul. no. 1297. ARS-USDA. Washington,
D.C.
Massoumi, A., and A. H. Cornfield. 1963. A rapid method for
determining sulfate in water extracts of soils. Analyst 88:321-
322.
Neller, J. R. 1952. Sulfur versus phosphorus for soils in pastures
of Florida. Soil Sci. Soc. Florida Proc. 12:123-127.
. 1959. Extractable sulfate-sulfur in soils of Florida in
relation to amount of clay in the profile. Soil Sci. Soc. Am.
Proc. 23:346-348.
Neller, J. R., G. B., Killinger, D. W. Jones, R. W. Bledsoe, and
H. W. Lundy. 1951. Fertilizer should contain a source of
sulfur for clover pastures in many areas of Florida. Agri. Exp.
Sta. Cir. S-35. University of Florida, Gainesville, Florida.
Stewart, B. A., and K. L. Porter. 1969. Nitrogen-sulfur relations
in wheat (Triticum aestivum), corn (Zea mays), and beans
(Pliaseolus vulgaris). Agron. J. 61:267-271.
Teman, G. L., S. E. Allen, and P. M. Giordano. 1973. Dry matter
yieldN and S concentration relationships and ratios in young
corn plants. Agron. J. 65:633-636.
Tisdale, S. L. 1977. Sulfur in forage quality and ruminant nuti-
tion. Tech. bul. no. 22. The Sulphur Institute. Washington,
D. C.
The Response of the Three Perennial Warm-Season Grasses
to Fertilizer Nitrogen on Eaugallie Fine Sand
(Alfic Haplaquod) in Central Florida1
W. G. Blue, C. L. Dantzman, and V. Impithuksa2
ABSTRACT
Three warm-season perennial grassesPensacola
bahiagrass (Paspalum notatum Fliigge), Ona stargrass
(Cynoclon nlemfuensis Vanderyst var. nlemfuensis), and
Transvala digitgrass (Digitaria decumbens Stent.)
were compared for response to applied N on EauGallie
fine sand (Alfic Haplaquod) at the Agricultural Re-
iFlorida Agricultural Experiment Stations Journal Series No.
2250.
^Professor, Soil Science Department; Associate Professor, Agri
cultural Research Center (Ona); and former graduate student,
Soil Science Department (presently Assistant Professor, Soil Sci
ence Department, Kasetsart University, Bangkok, Thailand), re
spectively, University of Florida, Gainesville, FL 32611.
search Center, Ona, Florida. The experiment was a
split-plot design with plant species as main plots and
N rates0, 112, 224, and 336 kg/ha/yearas subplots.
Lime, S, and micronutrients were applied uniformly,
and P and K in a 2:0.4:1.6 ratio with the N applied.
Forage was harvested four times/year, and macro
nutrients were applied two times/yearone half at the
beginning of the growing season in March and one
half after the second harvest approximately 1 July.
Grasses were planted on 3 October 1974; differential
fertilization and forage harvests were made from 1975
through 1979. Forage yields were very large in 1975,
especially from Ona stargrass and Transvala digitgrass,
compared with succeeding years. Forage N contents for

45
Proceedings, Volume 39, 1980
1975 were also large compared with succeeding years;
they were approximately two times as large from Ona
stargrass and Transvala digitgrass as from the Pensa
cola bahiagrass. Stolon-root mass and N content at the
end of 1975 from Pensacola bahiagrass were approxi
mately twice those from Ona stargrass and four times
those from Transvala digitgrass. Biomass yields from
Pensacola bahiagrass and Ona stargrass for 1975 were
larger than from Transvala digitgrass, but biomass N
was larger from Ona stargrass than from Pensacola
bahiagrass and Transvala digitgrass. The large bio
mass production and N contents during the first year
were primarily a consequence of enhanced mineraliza
tion of soil N following application of lime and dis
turbance of this virgin soil. Subsequently, forage pro
duction and N contents were comparable to those
from other long-term experiments; growth response to
N rates differed for the three grasses, but maximum
forage yields were similar. Stolon-root mass from Pensa
cola bahiagrass at the end of each season was approxi
mately twice that from Ona stargrass and three times
that from Transvala digitigrass. In spite of differences
in stolon-root masses, forage N contents of the three
species in response to increasing N rates were not dif
ferent and can be represented by the equation
Y = 25.3 + 0.397X + 0.0003X2
where Y = forage N contents and X = N applied,
each expressed as kg/ha.
Additional Index Words: Paspalum notatum
Flgge, Cynodon nlemfuensis Vanderyst var. nlem-
fuensis, Digitaria decumbens Stent., Spodosol, Nitro
gen uptake, Stolon-root mass, Biomass.
We have been studying N use efficiency primarily
by Pensacola bahiagrass (Paspalum notatum Flgge)
on Florida Spodosols and Entisols intensively for the
past 20 years. Several factors which can affect N losses
are leaching, denitrification, and NH3 volatilization.
Soil pH control, N sources, N rates, multiple N appli
cations, seasonal timing of N applications, effect of
stolon-ioot mass, rate of N absorption by plants, and
annual N fertilization repeated over several years have
been studied (1, 2, 3, 5, 6, 8, 9). These factors could
ultimately affect N utilization by plants. Of these, only
repeated annual N fertilization has given increased
N-use efficiency. Increased N uptake with time was
due in part to development of a relatively stable
stolon-root mass with respect to immobilization of N
and perhaps to mineralization of N immobilized
temporarily in soil organic matter.
Pensacola bahiagrass develops a large stolon-root
mass with N rates of 100 kg/ha/year or more. Nitrogen
concentrations and contents in the stolon-root mass
depend on N rates (4). Nitrogen absorption rates are
dependent on N application rate and may be as high
as 6 kg/ha/day (8). This absorbed N, depending on
temperature and soil moisture, may be stored in the
stolon-root system and translocated as needed for top
growth. Many perennial grass species that have been
introduced have smaller, less permanent stolon-root
massees than the bahiagrass. Differences in plant
morphology could affect N absorption rates, partic
ularly during adverse climatic periods for plant growth.
The objectives of this experiment were to compare
Pensacola bahiagrass which has a large, relatively
permanent stolon-root mass with two speciesOna
stargrass (Cynodon nlemfuensis Vanderyst var. nlem
fuensis) and Transvala digitgrass (Digitaria decumbens
Stent.)which have smaller, less permanent systems for
growth response to fertilizer N and N uptake in plant
components.
MATERIALS AND METHODS
The experiment was established on virgin Eau-
Gallie fine sand (sandy, siliceous, hyperthermic Alfic
Haplaquod) at the Agricultural Research Center (Ona)
in central Florida. A cultivar of each of three grass
speciesPensacola bahiagrass, Ona stargrass, and
Transvala digitgrassconstituted the main plots which
were 5 X 10 m. Four N rates were the subplots and
were 2.5 X 5 m. There were four replications. Borders
between replications were 3 m wide.
The soil received 3.75 metric tons/ha each of
calcitic and dolomitic lime on 15 August 1974 prior to
planting the grasses on 3 October; 54, 12, and 22 kg of
N, P, and K/ha, respectively, were applied on 10
October following planting. A micronutrient frit was
applied uniformly to all plots also on 10 October 1974
at 34 kg/ha and gypsum was applied annually at 240
kg/ha to supply adequate S. Nitrogen was applied
annually at rates of 0, 112, 224, and 336 kg/ha as
NH.jNOj with one half applied during the latter part
of March and one half following the second forage
harvest on approximately 1 July. Phosphorus as triple
superphosphate and K as KC1 were applied with the
N to give a N:P:K ratio of 2:0.4:1.6 (N:P205:K20
ratio of 2:1:2); the 0 and 112 kg/ha N rates received
the same amounts of P and K. Forage was harvested
four times per year as nearly as possible to 15 May, 1
July, 10 August, and 1 October. Pensacola bahiagrass
was harvested to a 3-cm stubble while Ona stargra
and Transvala digitgrass were cut 7 cm above the soil
surface. Stolon-root samples were collected after the
fourth forage harvest on 1 October of each year. Stolon-
root samples were washed thoroughly with tap water
and rinsed in distilled water to remove soil. All plant
tissues were dried at 70 C, ground by a Wiley mill to
pass a 20-mesh screen, and analyzed for total N by a
micro-Kjeldahl method which employed salicylic acid
and sodium thiosulfate for reduction of nitrates.
Data were analyzed statistically by analyses of vari
ance; treatment means were compared with Duncans
new multiple range test.
RESULTS AND DISCUSSION
Forage yields were relatively large in 1975 for each
of the grasses at all N rates, and particularly so from
Ona stargrass and Transvala digitgrass (Table 1).
Nitrogen contents of forage were also large. This was
not only a consequence of the fertilizer N, but also of
rapid mineralization of a fraction of the soil N after
application of lime and disturbance of this virgin
soil (7). In contrast to forage production, the stolon-
root mass from Pensacola bahiagrass at the end of
1975 was approximately two times that from Ona star-
grass and four times that from Transvala digitgrass.
Quantities of N in stolon-root systems were in approxi
mately the same proportion as stolon-root masses. Bio
masses from Pensacola bahiagrass and Ona stargrass

46
Soil and Crop Science Society of Florida
TABLE 1.Yield and nitrogen uptake by three perennial, warm-season grasses in response to
FERTILIZER N ON EAUGALLIE FINE SAND.
Annual
1975
Average 1976-79
Total
N
Plant species
rate
PB
Ona Trans
Avg
PB
Ona Trans
Avg
PB
Ona Trans
Avg
kg/ha Oven-dry forage, kg/ha
0
112
224
336
Avg
4690
8220
9030
10940
8220c
11490
17450
17670
20260
16720a
10770
14990
14780
14690
13810b
8980cf
13550b
13830ab
15300a
2600
6020
10110
13580
8080b
0
14630
8440
3600
8890a
13070
112
16170
9580
3920
9890a
19460
224
14030
8720
3560
8770a
21570
336
17170
5820
3850
8950a
20780
Avg
15500a
8140b
3730c
18720a
2010
3660
2760d
15050
19550
25400
20000d
5530
8240
6600c
32300
39600
47950
39950c
9460
11860
10480b
49500
55500
62200
55730b
11790
12720
12700a
65250
67400
65550
66070a
7200b
9120a
40530c
45510b
50280a
dry stolons + roots, kg/ha
6150
6120
8450b
8480
7570
11840a
9130
6660
12450a
6880
5180
10950a
7660b
6380b
0
19330
19930
14370
17880b
29000
23720
32290
28340a
112
24390
27030
18910
23440a
51490
47260
55810
51520c
224
23060
26390
18340
22600a
71420
63240
62200
65620b
336
28110
26080
18540
24240a
87050
73330
65550
75310a
Avg
23720a
24860a
17540b
59740a
51890b
53960ab
Forage N, kg/ha .
0
51
105
99
85d
28
21
31
27d
165
185
220
190d
112
114
204
170
163c
70
64
78
71c
394
460
483
446c
224
131
246
188
188b
130
130
138
133b
695
770
740
735b
336
178
279
226
228a
194
197
184
192a
955
1070
965
997a
Avg
119c
209a
171b
106a
103a
108a
552b
621a
602a
Stolon-root
N, kg/ha
0
51
41
16
36b
45
32
24
34d
112
72
51
21
48ab
72
50
36
53c
224
86
54
20
53ab
105
69
38
71b
336
137
38
24
66a
142
57
35
78a
Avg
87a
46b
20b
91a
52b
33c
Biomass N, kg/ha
0
102
146
115
121c
217
201
245
22 Id
112
186
255
191
211b
466
501
518
495c
224
217
300
208
242b
818
829
775
807b
336
315
317
250
294a
1110
1118
1002
1077a
Avg
205b
255a
191b
653ab
662a
635b
(Means within columns and lines within subtables followed by the same letter are not significantly different at the 0.05 probability
level according to Duncans new multiple range test.
for the first year were approximately the same and
substantially larger than the biomass from Transvala
digitgrass. Utilization of photosynthate and N for
production of the larger stolon-root mass by Pensacola
bahiagrass obviously reduced forage production dur
ing the developmental period in comparison with the
other two grasses which have relatively small stolon-
root systems.
For years 1976 through 1979, forage production
from the three grasses at the highest N rate was not
significantly different, but production at other N rates
did differ. Response of the three grasses to N rates can
be characterized by the following equations where
Y = oven-dry forage yields and X = N rates, both
expressed as kg/ha.
Forage plants Regression equations
Pensacola bahiagrass Y = 2530 + 32.8X + 0.00IX2
Ona stargrass Y = 1920 + 37.2X 0.022X2
Transvala digitgrass Y = 3610 + 54.1X 0.081X2
Growth response characteristics of the three grasses
were likely related to absorption and storage of N in
the stolon-root systems, and perhaps to some N im
mobilization in dead, partially decomposed stolon-root
tissues. Thus, forage production from Transvala digit-
grass with the smallest stolon-root system was largest
at low N rates and from Pensacola bahiagrass the
smallest.
Nitrogen uptake in forage from 1976 through 1979
did not differ significantly among forage plants and
can be characterized by a single equation as follows
where Y = forage N and X = N applied, both ex
pressed as kg/ha.
Y = 25.3 + 0.397X + 0.0003X2
Stolon-root masses from Pensacola bahiagrass and
Transvala digitgrass increased somewhat from 1976
through 1979 in comparison with masses at the end of
1975, while Ona stargrass did not change appreciably.
Biomass production through 5 years, i.e., total
forage produced over the 5-year period plus stolon-root
mass at the end of the fifth year, was not drastically

47
Proceedings, Volume 39, 1980
different for the three grasses, but was significantly
larger from Pensacola bahiagrass than from Ona star-
grass. Biomass N for the three grasses through 5 years
was also similar.
Ona stargrass did not maintain a satisfactory stand
under the experimental conditions through the 5-year
period in comparison to Pensacola bahiagrass and
Transvala digitgrass. Since stolon-root samples were
taken only where grasses were present, stolon-root mass
and biomass from Ona stargrass were somewhat over
estimated.
LITERATURE CITED
1. Blue, W. G. 1966. The effect of nitrogen sources, rates, and
application frequencies on Pensacola bahiagrass forage yields
and nitrogen utilization. Soil and Crop Sci. Soc. Florida Proc.
26:105-109.
2. Blue, W. G. 1970. Fertilizer nitrogen uptakes by Pensacola
bahiagrass (Paspalum notatum) from Leon fine sand, a
Spodosol. XI Int. Grassland Congr. Proc., Surfers Paradise,
Australia. 389-392.
3. Blue, W. G. 1972. Nitrogen fertilization in relation to seasonal
Pensacola bahiagrass forage nitrogen and production distribu
tion. Soil and Crop Sci. Soc. Florida Proc. 31:75-77.
4. Blue, W. G. 1973. The role of Pensacola bahiagrass stolon-
root systems in fertilizer nitrogen utilization on Leon fine
sand. Agron. J. 65:88-91.
5. Blue, W. G. 1974. Efficiency of five nitrogen sources for
Pensacola bahiagrass on Leon fine sand as affected by lime
treatments. Soil and Crop Sci. Soc. Florida Proc. 33:171-180.
6. Blue. W. G. 1977. Comparison of sulfur-coated urea and am
monium nitrate for Pensacola bahiagrass on a Florida
Spodosol. Soil Sci. Soc. Am. J. 41:1191 -1193.
7. Blue, W. G., C. F. Eno, N. Gammon, Jr., and D. F. Rothwell.
1964. Timing liming applications to obtain the maximum
beneficial effect in clover-grass pasture establishment on
virgin flatwoods soil. Soil and Crop Sci. Soc. Florida Proc.
24:162-166.
8. Blue, W. G., and D. A. Graetz. 1977. The effect of split nitro
gen applications on nitrogen uptake by Pensacola bahiagrass
from an Aerie Haplaquod. Soil Sci. Soc. Am. J. 41:927-93(1.
9. Mata, A., and W. G. Blue. 1974. Fertilizer nitrogen distribu
tion in Pensacola bahiagrass sod during the first year of de
velopment on an Aerie Haplaquod. Soil and Crop Sci. Soc.
Florida Proc. 33:209-211.
Mobility and Extractability of Phosphorus
Applied to the Surface of Tifway Bermudagrass Turf1
J. B. Sartain2
ABSTRACT
A field-plot experiment was initiated on Tifway
bermudagrass [Cynodon dactylon (L.) Pers.] turf to
study the effect of time on the extractability of P by
different soil extractants and to evaluate the extent of
downward movement of applied P. Three replications
of five rates of P (0, 98, 197, 394, and 788 kg/ha) were
established in a randomized complete block design on
3 by 4 m plots. Soil samples were collected monthly
during the first 6 months and approximately every 45
days during the remainder of the 15-month sampling
period. Each sample was divided into three sections by
depth (0 to 5, 5 to 20, and 20 to 30 cm). Phosphorus
status of each sample was determined in the following
extractants: IN NH4C1; 0.0021V H,S04; NH4OAc, pH
4.8; 0.0251V H2S04 in 0.05V HC1; and 0.03 N NH4F in
0.11V HC1. Total P was determined on selected sam
plings by the perchloric acid procedure.
Readily extractable NH4C1-P equilibrated with the
soil within the first 6 months of the 98 kg/ha P appli-
tions and was reduced to extractable levels near those
of the control plots. Ammonium chloride extractable
P was reduced by 70% during the first 6 months but
had not reached the P level extracted prior to the ap
plication of 788 kg/ha P. Truog, NH4OAc, and double
acid extractable P decreased by similar percentages
during the first 6 months, but only about 30 % as much
as the NH4C1-P n plots receiving 98 kg/ha P. Double
acid and Bray-2 extractable P had not stabilized 15
months after 788 kg/ha P was applied. Small increases
in readily extractable and double-acid P were noted at
iFlorida Agricultural Experiment Stations Journal Series No.
2259.
2Associate Professor of Soil Fertility (Turf and Ornamentals),
Soil Science Department, University of Florida, Gainesville, FL
32611.
the 5 to 20-cm depth from the application of 98 kg/ha
P. Large increases in the double-acid soluble P were
observed after 3 months at the 5 to 20-cm depth where
788 kg/ha P were applied. Phosphorus did not leach
below the 20-cm zone during the first 15 months.
Additional Index Words: Extractable P, Readily
soluble P, Total P, Soil phosphate complexes.
Phosphorus accumulation has been studied in many
soils as part of the problem of assessing P availability
to crops. The usually small amount of accumulated P,
relative to the larger amounts of native P in phosphatic
soils, has prevented an accurate evaluation of the forms
in which P compounds exist.
Dicalcium phosphate (DCP) was shown to be a
major initial product in soils that had received mono
calcium phosphate (MCP). This product (DCP) forms
by hydrolysis around granules of MCP (10). The re
sultant acidity solubilized appreciable Ca, Al, Fe, and
Mn (10). These dissolved ions were shown to be in
corporated in subsequent P precipitation (10).
In laboratory tests, Yuan et al. (19) reported that
applications of water-soluble P quickly reverted to the
Al forms in three sandy Florida soils. Fiskell and
Rowland (5) used sequential extractions and total
analysis to show that Al and Fe phosphates were the
major forms present in both phosphatic and non-
phosphatic Florida soils.
Aluminum-P is the fraction most commonly re
ported as being correlated with plant-available P on
acid to nearly neutral soils (7, 11, 15). The Ca-P form
contributes significantly to the P supply on recently
fertilized soils and acid soils fertilized with rock phos
phate (4).
The extractability of various P fractions can be

48
Soil, and Crop Science Society of Florida
summarized according to the principle ions used in the
soil extractant. Hydrogen ions remove fractions in the
order Ca-P > Al-P > Fe-P; hydroxide ions in the order
Fe-P > Al-P; bicarbonate ions in the order Al-P > Fe-P
Ca-P; fluoride ions in the order Al-P > Fe-P > Ca-P;
and acetate ions in the order Al-P > Ca-P > Fe-P (3,
6, 11, 12, 15, 16).
Humphreys and Pritchett (8) reported little or no
residual P from superphosphate remained in the top
20 cm of soils with little P sorption or buffering capac
ity, such as a Leon fine sand over a period of 7 to 10
years. Almost all of the applied P remained as an avail
able form in the rooting zone in soils with a low P
sorption and buffering capacity; whereas, in a soil with
high P sorption and buffering capacity, most of the
added P was retained in the surface horizon in forms
of limited availability. Ballard and Fiskell (2) reported
that most of the sandy soils of the Southeastern Coastal
Plains have a very small retention capacity for water-
soluble P against leaching, but that the surface hori
zons of Spodosols had the lowest retention capacities.
Linear adsorption isotherms were reported for most of
the Spodosols, but isotherms for Ultisols, Inceptisols,
and Entisols were non-linear. In a lysimeter study,
Neller (13) reported that in 4 months 72.4 cm of rain
fall leached more than 70% of applied superphosphate-
P from the surface 20 cm of a Leon fine sand.
The objectives of this study were: (1) to determine
the effect of time on the quantity of P extracted by dif
ferent extractions; and (2) to determine the extent of
downward movement of P applied to the surface of
bermudagrass [Cynodon dactylon (L.) Pers.] turf.
MATERIALS AND METHODS
Experimental 3 x 4 m plots were established on a
healthy stand of Tifway bermudagrass at the Horti
cultural Unit near Gainesville in a randomized com
plete block design. Three treatment replications of P
were applied at 0, 98, 197, 394, and 788 kg/ha as con
centrated superphosphate. Phosphorus was applied in
solution at 16 liters per plotthis volume permitted
uniform coverage of the 12 m2 with minimum penetra
tion of the soil profile. Nitrogen and K were applied at
an annual rate of 400 and 200 kg/ha as NH4N03 and
KC1, respectively, to all plots.
Soil samples were collected every 30 days during the
first 6 months after treatment application and approxi
mately every 45 days during the succeeding 9 months.
The ten cores of each sampled profile were divided into
three sections0 to 5, 5 to 20, and 20 to 30 cm. All
samplings for the 15-month period were analyzed for
P by extraction with the solutions listed in Table 1.
Total P by the perchloric acid oxidation procedure
(9) was determined on selected samplings. Only data
involving the 98 and 788 kg/ha P treatments are dis
cussed in this study because of the large volume of data
obtained. The other P treatments showed similar
trends.
The soil on which the bermudagrass was established
is an Arredondo fine sand (loamy, siliceous, hyper
thermic family of Grossarenic Paleudult) which has a
high total native P status. A few weathered and leached
phosphatic pebbles ranging in diameter from 2 to
20 mm were found scattered throughout the profile.
Chemically this soil had a pH of 6.1, CEC of 9.6, and a
negligible level of IN KC1 extractable Al.
TABLE 1Phosphorus extraction methods.
Method
Extractant
pH
Soil:
Solu
tion
Shaking
Time
Ref.
NH Cl
4
IN NH Cl
4
3.0
1:10
minutes
30
16
T ruog
0.002N H,S04 +
3g(NH4)S04/l
3.0
1:100
30
17
NH.OAc
4
0.7N NH4OAc +
0.5N CH3CooH
4.8
1:5
30
14
Double-acid
0.05N HCI +
0.025N H2S04
1.3
1:4
5
14
Bray-2
0.03N NH4F +
0.1N HCI
1.3
1:10
1
14
Total P
HCIO.
4
-
1:10
-
9
RESULTS AND DISCUSSION
Soil P status prior to treatment application for
three segments of the top 30 cm of the profile is given
in Table 2. Ammonium chloride extractable P was
shown to correlate strongly (r = .95) with the water-
soluble P fraction of the soil (16). The top 5 cm con
tained a relatively high level (4 ppm) of NH4C1-
soluble P, while less P was soluble at the two lower
depths. Previously applied fertilizer P could account
for the observed P status of the surface sample. Truogs
solution (0.002N H2S04) removed more P than IN
NH.jCl. Researchers (18) in the past have correlated
Truog extractable P with portions of the Ca-P and
Al-P fractions. Ammonium acetate, pH 4.8 solubilized
approximately twice as much P as 0.002N H2S04 in
the top 5 cm and about three times as much in the 5
to 20 and 20 to 30-cm sections. Acetate ions reportedly
solubilize more Al-P than do H ions (1). Since the
high P status of the 0 to 5-cm section was most likely
due to the application of Ca-P and a higher proportion
of Al-P was probable at the lower soil depths, the
greater relative P solubility with NH4OAc, pH 4.8 at
the lower depths could have been due to Al-P.
Mehlichs double-acid extractant solubilized more than
five times as much P as did the NH4OAc, pH 4.8 in
the surface 5 cm. The lower pH (1.3) of the double
acid extractant and its stronger affinity for dissolution
of Ca-P accounted for this increased P extraction.
Bray-2 extractant is reported to solubilize more Fe-P
TABLE 2.Soil P status prior to treatment application by
DIFFERENT EXTRACTANTS AND DEPTHS.
Depth (,cm)
0 to 5 5 to 20 20 to 30
IN NH4C1
0.002N HS04
NH4OAc,pH 4.8
0.05N HC1 in 0.025N H.,S04
0.03N NH4F in 0.1N HCI
Total P
P, ppm (%)f
4.4 (0.5) 0.5 (0.07) 0.6 (0.09)
17.1 (2) 4.7 (0.7) 4.5 (0.7)
34.0 (4) 12.8 (2) 12.9 (2)
191.9 (23) 117.4 (18) 104.4 (17)
335.5 (41) 281.7 (44) 234.7 (38)
882.3 637.7 614.4
fEntries in parenthesis are percentages of total P.

49
Proceedings, Volume 39, 1980
and Al-P than the other extractants because of the
acid strength and the presence of the complexing
fluoride ions (1). Approximately the same amount (ca
40%) of the total P was removed by the Bray-2 ex
tractant at all three soil depths. Since this extractant
solubilized proportionally more Fe-P and Al-P and the
quantity of free Fe and A1 was typically low in this
soil, most of the P remained in the Ca-P form and was
not readily solubilized by the Bray-2 extractant. Total
P reserves in this soil prior to the initiation of the
study were very high and the probability of a response
to applied P fertilizer was small.
One month after application of 98 kg/ha of P as
TSP, the NH.jCl-P in the 0 to 5-cm layer was 10 ppm
higher than prior to addition of P (Table 3). During
the following 6 months, the readily soluble P level
dropped by 53% to near the level prior to application,
indicating that the MCP contained in the TSP was
gradually converted to more insoluble P forms. Phos
phorus solubility by Truog, NH,OAc, and double-acid
extractants decreased by similar percentages during
the first 6 months despite the large differences in the
quantities of P extracted. The relatively small reduc
tion of the Truog P (which has been shown to corre
late with Ca-P, such as DCP) suggested that a signif
icant portion of the P at the end of 6 months was still
in a dilute acid soluble form. Bray-2 extractable P was
not significantly reduced during the first 6 months. A
very small portion of the applied P was converted to
sparingly soluble P forms of adsorbed or occluded P.
Total P decreased by 0.1% in the top 5 cm which was
probably the resultant of plant uptake.
The data for the 15-month sampling period can be
divided into two distinct groups (Table 3). Most of
the change in the readily soluble P occurred within
the first 6 months. During the 9 to 15-month period,
the level of P solubilized by the dilute acid and salt
extractants remained static. Bray-2 was reduced by ap
proximately 11% during the 9 to 15-month period in
dicating that change was still occurring in the more
insoluble A1 and Fe-P compounds.
Almost identical trends in P solubility were ob
served during the first 6 months in plots receiving a
high level (788 kg/ha) of P (data not shown). The
primary difference between the 788 and 98 kg/ha P
treatments was the magnitude of the reduction in ex
tractable P status with time. Since a larger decrease in
total P was observed (8.2%), it was suggested that a
significant portion of the reduction in P status for all
extractants was due to the downward displacement of
the applied P.
Where P was applied at a typical rate (98 kg/ha),
the level of NH4Cl-soluble P did not increase greatly
in the sampled sections below 5 cm (Table 4). The
slight increase in NFI.,Cl-extractable P in the 5 to 20-cm
section could have resulted from the method of appli
cation. The treatments were applied in solution; there
fore, the P may have moved with the water during
initial treatment even though the P was applied in 16
liters of solution to the 12 m2 area. Initial application
conditions do not explain the changes which occurred
with time by depth in the NH4C1-P on plots receiving
788 kg/ha P since a high level of P was not detected at
the 25 March sampling. Soil NH4Cl-extractable P in
creased in the 5 to 20-cm section during the first 4
months after application, indicating the downward
movement of P from the surface and retention of this
readily soluble P fraction in the 5 to 20-cm zone. At no
TABLE 3.Effect of time on the solubility of P with a low level of applied P.
Months 1 thru 6 Months 9 thru 15
Sampling dates (1976) % Sampling dates (1976-77) %
Extractant
25 Mar
22 Apr
20 May
25 June
19 Aug
reduction
3 Nov
15 Dec
2 Mar
25 May
reduction
_ P, ppm .
P,
ppm
nh4ci
14.2
12.9
13.5
10.0
6.6
53.5
5.2
4.8
7.1
5.9
0
T ruog
30.2
29.3
33.7
32.3
26.0
14.0
23.3
22.7
25.5
21.8
6.4
NH(OAc
52.0
48.7
54.0
42.6
42.6
18.1
40.0
39.7
38.9
40.6
0
Double acid
266.7
212.3
258.1
261.8
226.2
15.2
216.7
223.8
215.2
220.5
0
Bray 2
406.8
401.3
384.0
384.0
396.3
2.3
386.2
320.7
362.6
344.0
10.9
Total P

863.9

875.2
855.7
0.1
843.7


832.5
1.3
Sampling Depth: 0 to 5 cm
P Application: 98 kg/ha
TABLE 4.Downward movement of NH.CI-soluble P in response to two levels of applied P
4
WITH TIME.
P Sampling dates (1976-77)
Depth
Applied
5 Feb
25 Mar
22 Apr
20 May
25 June
19 Aug
3 Nov
15 Dec
2 Mar
25 May
cm
kg/ha
P,
0 to 5
98
4.5
11.1
12.9
13.5
10.0
6.6
5.2
4.8
7.1
5.9
5 to 20
98
0.3
0.6
0.8
0.9
0.6
0.9
0.7
0.6
0.6
0.6
20 to 30
98
0.4
0.1
0.9
0.5
0.5
0.5
0.5
0.1
0.4
0.2
0 to 5
788
4.2
82.4
69.4
47.4
36.4
24.2
19.2
19.6
20.5
14.3
5 to 20
788
0.3
1.4
4.0
6.1
6.0
3.8
3.7
4.6
3.7
5.6
20 to 30
788
0.4
0.2
1.0
0.6
0.4
0.6
0.5
0.2
0.6
0.1

50
Son. and Crop Science Society of Florida
TABLE 5.Downward movement of double-acid soluble P in response to two levels of applied
P WITH TIME.
P Sampling dates (1976-77)
Depth
Applied
5 Feb
25 Mar
22 Apr
20 May
25 June
19 Aug
3 Nov
15 Dec
2 Mar
25 May
cm
kg/ha
P;
0 to 5
98
195
267
212
258
262
226
217
223
215
220
5 to 20
98
108
118
117
105
112
131
115
123
129
104
20 to 30
98
95
87
90
87
89
97
93
104
99
95
0 to 5
788
209
851
790
753
707
528
499
552
489
386
5 to 20
788
136
182
159
255
266
228
235
252
233
233
20 to 30
788
87
77
74
75
74
91
83
105
87
94
sampling time during the 15-month period was an in
crease in NH.jCl-extractable P observed in the 20 to
30-cm section.
Small and erratic fluctuations o£ the double-acid P
status of the 5 to 20-cm zone were noted where 98
kg/ha P was applied (Table 5). These increases and
decreases in P status may have been influenced more
by the environment and plant uptake than by the
movement of P through the profile. Plots receiving
788 kg/ha P had not equilibrated with respect to
double-acid soluble P in the 0 to 5-cm layer even after
15 months. After about 3 months, the double-acid
soluble P level reached a maximum in the 5 to 20-cm
section and began to decrease with time, but not to
the P level prior to P application. No change in the P
status of the 20 to 30-cm section was observed for
either the high or low P application. A more informa
tive sampling would have involved the division of the
5 to 20-cm section into more than one section and the
exclusion of the 20 to 30-cm zone.
LITERATURE CITED
1. Ballard, R. 1974. Extractability of reference phosphates by
soil test reagents in absence and presence of soils. Soil Crop
Sci. Soc. Florida Proc. 33:169-174.
2. Ballard, R., and J. G. A. Fiskell. 1974. Phosphorus retention
in Coastal Plain Forest Soils: 1. Relationship to soil prop
erties. Soil Sci. Soc. Am. Proc. 38:250-255.
3. Chang, S. C., and S. R. Juo. 1963. Available phosphorus in
relation to forms of phosphorus in soils. Soil Sci. 95:91-96.
4. Chu, C. R., W. W. Moschler, and G. W. Thomas. 1962. Rock
phosphate transformations in acid soils. Soil Sci. Soc. Am.
Proc. 26:476-478.
5. Fiskell, J. G. A., and L. O. Rowland. 1960. Soil chemistry of
subsoils of west central Florida. Soil Crop Sci. Soc. Florida
Proc. 20:123-128.
6. Grigg, J. L. 1965. Inorganic phosphorus fractions in South
Island soils and their solubility in commonly used extracting
solutions. N. Z. J. Agrie. Res. 8:313-326.
7. Grigg, J. L. 1968. Prediction of plant response to fertilizer by
means of soil tests: II. Correlations between soil phosphate
tests and phosphate response to ryegrass grown in pot experi
ments on recent, gley recent, and gley soils. N. Z. J. Agrie.
Res. 11:345-358.
8. Humphreys, F. R., and W. L. Pritchett. 1971. Phosphorus
adsorption and movement in some sand forest soils. Soil Sci.
Soc. Am. Proc. 35:495-500.
9. Jackson, M. L. 1958. Soil chemical analysis. Prentice-Hall,
Inc. Englewood Cliffs, N. J.
10. Lindsay, W. L., A. W. Frazier, and H. F. Stephenson. 1962.
Identification of reaction products from phosphate fertilizers
in soils. Soil Sci. Soc. Am. Proc. 26:446-452.
11. Martens, D. C., J. A. Lutz, and G. O. Jones. 1969. Form and
availability of P in selected Virginia soils as related to avail
able P tests. Agron. J. 61:616-621.
12. McLachlan, K. D. 1965. The nature of available phosphorus
in some acid pasture soils and a comparison of estimating
procedures. Aust. J. Expt. Agrie. An. Husb. 5:125-132.
13. Neller, J. R. 1946. Mobility of phosphates in sandy soil. Soil
Sci. Soc. Am. Proc. 11:227-230.
14. Page, N. R., G. W. Thomas, H. F. Perkins, and R. D. Rouse.
1965. Procedures used by state soil-testing laboratories in the
southern region of the United States. Southern Cooperative
Series Bull. No. 102.
15. Payne, H., and W. J. Hanna. 1965. Correlations among soil
phosphorus fractions, extractable phosphorus, and plant con
tent of phosphorus. J. Agrie. Food Chem. 13:322-326.
16. Pratt, P. F., and M. J. Garber. 1964. Correlations of phos
phorus availability by chemical tests with inorganic phos
phorus fractions. Soil Sci. Soc. Am. Proc. 28:23-29.
17. Sherreli, C. G. 1970. Comparison of chemical extraction
methods for the determination of available phosphate in
soils: I. Correlation between methods and yield and phos
phorus uptake by white clover grown on the 16 North Island
soils in the glasshouse. N. Z. J. Agrie. Res. 13:481-493.
18. Susuki, A., K. Lawton, and E. C. Doll. 1963. Phosphorus up
take and soil tests as related to forms of phosphorus in some
Michigan soils. Soil Sci. Soc. Am. Proc. 27:401-403.
19. Yuan, T. L., W. K. Robertson, and J. R. Neller. 1960. Forms
of newly fixed phosphorus in three acid sandy soils. Soil Sci.
Soc. Am. Proc. 24:447-450.

Proceedings, Volume 59, 1980
51
Growth Responses of Young Slash Pine to Site Preparation
and Fertilization on Poorly Drained Soils1
W. L. Pritchett and E. G. Flaig2
ABSTRACT
Seven uniform experiments were established on a
range of poorly drained soils in the lower coastal plain
to evaluate the effects of site preparation on survival
and early growth of slash pine (Pinus elliottii var.
elliottee Engelm.) and the feasibility of substituting
fertilization for the more expensive site preparation
practices. Tree heights were significantly increased by
the more intensive preparation treatments (disking
and bedding) and by fertilization with P and N + P, 5
to 8 years after treatment. There were no interactions
between the two types of treatments and their effects
were generally additive. Tree growth rates declined on
bedded plots, in relation to control plots, after 5 years.
Response to fertilizers also declined on some soils, but
early differences in heights were maintained for at
least 8 years. There were relatively few significant
effects of treatments on nutrient concentrations in
needles, except for P. Double-acid extractable A1 was
significantly decreased by site preparation of Ultic
Haplaquods. Bulk density was slightly increased by
chopping in three of nine selected blocks, but bedding
had no significant effect on bulk density after 8 years.
At this stage of plantation development, total biomass
of understory vegetation did not differ significantly
among treatments.
Additional Index Words: Forest nutrition, Forest
soils, Phosphate fertilization, Bedding, Pinus elliottii.
Forest management in the southeastern United
States stresses the regeneration of pines in plantations,
and approximately 8 million hectares of pine are pres
ently grown in plantations in the area. Plantation
forestry allows the use of heavy equipment for slash
reduction, soil amelioration, and facilitation of plant
ing. Slash pine (Pinus elliottii var. elliotlii Engelm.), a
fast growing, shade-intolerant species, responds well to
evenaged, intensive plantation management. This
often involves the use of machinery for seedbed prep
aration, a practice used on many sites to insure ade
quate seedling survival and early tree growth, and to
reduce competing vegetation.
Shearing blades, rootrakes, and disk harrows are
often used in site preparation, particularly on sites
with considerable hardwood vegetation. However,
these operations not only reduce competing vegetation,
but may also drastically disturb the surface soil and
the blades and rakes may remove much of the forest
floor and surface soil organic matter into windrows.
While these treatments often improve seedling survival
and early growth as a result of reduced competition
from understory vegetation and increased soil nutrient
iFlorida Agricultural Experiment Stations Journal Series No.
2283.
2Pro£essor Forest Soils and Graduate Assistant, respectively,
Soil Science Department, University o£ Florida, Gainesville, FI.
32611. The authors acknowledge the assistance of the Coopera
tive Research in Forest Fertilization (CRIFF) program for the
installation, measurements, and maintenance of the field in
stallations.
availability, they may be at the expense of long-term
site productivity (Haines et al 1975).
A series of field experiments was installed on rep
resentative soil-site types of the lower coastal plain to
determine tree response to site preparation, the in
fluence of site preparation on fertilizer effectiveness,
and whether the use of fertilizers can be substituted,
in part, for certain site preparation operations.
MATERIALS AND METHODS
Slash pine responses to three types of site prepara
tion in factorial combination with three fertilizer treat
ments were measured at seven lower coastal plain sites
for 8 years after planting. Four replications of 27 x
30 m plots in a 3 x 3 factorial experiment, where site
preparation treatments formed whole-plots and fertil
ization treatments comprised sub-plots, were installed
at each site.
The site preparation (whole-plot) treatments were
(a) chopa minimum preparation consisting of slash
burning and a single pass with a drum chopper, (b)
disksingle disking in addition to a prior burn and
chop, and (c) bedstandard ridging with a disk harrow
following burning and chopping.
The fertilizer (sub-plot) treatments consisted of (a)
noneno nutrients added, (b) CSP45 kg P/ha ap
plied as concentrated superphosphate, and (c) DAP-
40 kg N plus 45 kg P/ha applied as diammonium phos
phate. Fertilizer materials were broadcast-applied over
the entire plot surface within 2 to 3 months after plant
ing 1-0 seedlings. Nine-meter wide 3 rows) buffer
strips were left on all sides of the 21 x 24 m net sub
plots.
Tree-height measurements were made at 3, 5, and
8 years after treatment (except that not all tests were
measured at 8 years). Tree-survival percentage was
calculated at 3 years after planting and percentages of
trees damaged by disease (stem canker) were deter
mined at each measurement period.
Soils were initially surveyed to ensure that each
replication blocked a homogenous soil type, but there
was no requirement that all blocks at each site be
established on the same soil type. Therefore, two or
more soil series were often present at a given test site.
In order to gain a better understanding of the effects
of soil properties on responses, blocks containing sim
ilar soils across all test sites were grouped on the basis
of those profile and drainage characteristics thought
to influence tree response to site preparation and fertil
ization. Twenty-three of the more uniform blocks were
selected for this study and combined into four soil
groups for statistical analyses and discussion, as shown
in Table 1. Group A soils were Aquults, group B con
sisted of poorly to very poorly drained sands and they
varied from Grossarenic Paleudults to Typic Huma-
quepts, group C soils were Ultic Haplaquods, and
group D soils were Aerie Haplaquods. Some chemical
properties of the principal horizons of the four groups
of soils are summarized in Table 2, for samples col
lected prior to treatment.

Soil and Crop Science Society of Florida
52
TABLE
1.Soil groups for site preparation
TERPRETATIONS.
FERTILIZATION IN-
Soil
Representative
soil series
Diagnostic Characteristics
group
Drainage class
B horizon
A (3)t
Portsmouth
Bladen types
Very poorly to
somewhat poorly
Argillic within
50 cm of surface
B (6)
Rutlege
Plummer types
Very poorly to
somewhat poorly
No spodic, argil
lic deeper than
50 cm
C (9)
Mascotte
Sapelo types
Poorly to some
what poorly
Spodic underlain
by argillic
D (5)
Ridgeland
Leon types
Poorly to mod
erately well
Spodic with no
underlying
argillic
+( ) indicates number of replications in each soil group.
TABLE 2.Mean soil chemical concentrations in principal
soil horizons by soil group in pre-treatment samples.
Total Double-acid extractable
Horizon
(H,0) OM N
P K Ca Mg
Fe
Al
7n
Soil group A (Shallow
argillic horizon)
Ai
4.49 4.12 0.102
1.3 23 63
31
147
271
A2t
4.42
0.6 8 75
33
67
259
Ct
4.73
0.3 17 12
70
38
253
Soil group B (Deep argillic horizon)
A1
4.92 3.97 0.077
0.6 19 75
12
59
322
A3
4.94
2.4 4 24
7
14
298
Ct
5.06
0.7 5 3
16
15
174
Soil group C (Spodic above argillic horizon)
A1
4.30 3.38 0.067
2.6 15 121
32
15
110
Bh
4.62
3.8 5 34
6
28
497
Ct
4.80
4.4 4 3
11
40
252
Soil group D (Spodic with
no argillic horizon)
A1
4.43 3.22 0.051
3.4 25 102
35
12
66
Bh
4.65
2.3 5 21
7
15
537
c
4.84
3.6 4 2
7
35
489
Soils were sampled from selected combinations of
site preparation-fertilization treatments 6 years after
planting. The control and the four combinations which
produced the greatest tree-height growth response at
age 5 years were sampled by horizons at six random
points in tree rows. Combinations of treatments sam
pled included (a) chopnone, (b) diskDAP, (c) bed
none, (cl) bedCSP, and (e) bedDAP. Samples were
analyzed for pH (1:2 soil-water suspension), organic
mater content (Walkley-Black), and double-acid (0.05N
HC1-0.025N HSO.,) extractable nutrients.
Foliage was collected from six dominant or codom
inant trees in plots from which soils were sampled.
Samples were preserved on ice until they could be
oven-dried at 65C. Total N was determined by the
macro-Kjeldahl procedure and K, Ca, Mg, Fe, and A1
were analyzed by atomic absorption techniques, after
ashing at 450 C. Phosphorus was determined colori-
metrically in ascorbic acid and molybdate-sulfuric acid
solutions (Jackson, 1958).
The effects of site preparation on soil bulk density
of the surface and B horizons were determined at three
test sites 6 years after treatment. Soils were sampled
witli a hammer-driven core sampler (Blake, 1965), after
excavating to within 2 cm of selected depth with a soil
auger.
The total biomass of understory vegetation was
measured at one test location 6 years after treatment.
For this purpose, five rectangular plots were randomly
established within each of the five selected treatments
of three blocks. Rectangular plots were 0.4 m wide and
extended from the base of a pine tree to a midpoint
between rows. All above-ground green biomass was
clipped, bagged, and dried to constant moisture at
60 C.
Tree growth data were statistically examined by
analysis of variance techniques for factorial experi
ments with unequal replications. Main effects for site
preparation and fertilizer treatments were obtained
for the study as a whole and by individual soil groups.
A stepwise multiple regression was used to regress
mean height and height increment against soil and
foliage chemical properties.
RESULTS AND DISCUSSION
Tree Growth Responses
Site preparation and fertilization treatments signif
icantly increased slash pine height growth when data
for all locations were combined. However, the mag
nitude and duration of the treatment responses de
pended on soil properties and data are discussed by soil
groups as described in Table 1.
Soil Group A (Shallow argillic B horizon): Slash
pine on these Aquults responded dramatically to both
site preparation and fertilization (Table 3), similar to
earlier results for wet savanna soils (Pritchett and
Smith, 1974). Trees on the minimally-prepared (chop)
treatment grew very poorly, averaging only 1.02 m
after 5 years. The main effect of site preparation on
tree growth was highly significant, and bedding re
sulted in better growth than either chop or disk treat
ments (Fig. la). Disking increased tree heights over
heights of trees in minimally-prepared plots an average
of 29% after 5 years, although this increase was not
statistically significant due to excessive between-plot
variation. On the other hand, trees in bedded plots
were almost twice as tall as trees in the minimally-
prepared plots when averaged across all fertilizer treat
ments, giving a highly significant response.
Bedding improved aeration in the rooting zone
during the first year after planting in these Aquult
soils. It may have improved nutrition of the young
trees by concentrating surface soil organic matter into
mounds where tree roots were largely confined during
the early years of stand establishment (Haines and
Pritchett, 1965) and by hastening organic matter de
composition and mineralization. Soil samples taken 6
years after treatment failed to indicate any significant
difference in concentrations of organic matter, total N,
or extractable P between the minimum treatment and
bedded plots in the absence of fertilizers. Tabular data
are not presented herein, in the interest of space, but
surface soil (A1 horizon) total N averaged 1.01 and
1.13%, and extractable P averaged 1.2 and 1.3 ppm in
the chopped and bedded plots, respectively.

53
Proceedings, Volume 39, 1980
Soil group A Soil group B
DAP CSP None
Soil group C
Soil group D
Fig. 1.Mean heights of 5-year-old slash pines in soils groups
A (Aquults), B (Grossarenic Paleudults to Typic Humaquepts),
C (Ultic Haplaquods), and D (Aerie Haplaquods) that received
three site preparation and three fertilization treatments in fac
torial combination.
The highly significant main effects of fertilizers on
tree heights at the end of 5 years are shown in Fig. la.
Height responses to CSP fertilizer amounted to a 91%
increase over the non-fertilized plots, while the re
sponse to DAP averaged 116% compared to non-
fertilized plots, when averaged across all site prepara
tion treatments. It is interesting to note that the cur
rent height increment during the fifth year amounted
to 123 and 132% more than the non-fertilized plots
for the CSP and DAP treatments, respectively (Table
3). This indicated that the magnitude of the response
to P fertilizers was still increasing. These large re
sponses were a consequence of the extremely low avail
able P in non-fertilized soils (only 1.3 ppm extractable
P). While the absolute increase in heights due to fer
tilization was greater on bedded plots than on disked
plots (2.02 vs. 1.72 m), the percent increase in height
TABLE 3.Mean annual height growth in the fifth year by
TREATMENT COMBINATIONS AND SOIL GROUPS.
Treatment
A (3)f
Soil group
B (6) C (9)
D (5)
Site
preparation
Fertilization
cm
Chop
none
24
48
68
58
Chop
CSP*
77
56
82
67
Chop
DAP*
85
58
85
60
Disk
none
38
57
82
68
Disk
CSP
97
64
87
77
Disk
DAP
101
63
94
83
Bed
none
72
63
94
78
Bed
CSP
125
66
93
74
Bed
DAP
114
64
101
81
CSP = concentrated superphosphate and DAP = diam-
monium phosphate, each applied at rate of 45 kg P/ha.
t( ) indicates number of replications in each soil group.
of fertilized trees over non-fertilized trees was greater
in disked plots than in bedded plots (122 vs. 78%),
because of the generally better growth on the latter
plots. In spite of these apparent differences, the inter
action between site preparation and fertilization was
statistically non-significant, indicating that the re
sponses to the two types of treatments were additive
and that one cannot effectively substitute for the other
on these Aquults (Fig. la).
Soil Group B (Argillic horizon deeper than 50 cm):
Site preparation and P fertilization significantly in
creased tree height growth on group B soils. The main
effects of site preparation were generally greater than
those associated with P fertilizers, after 5 years (Fig,
lb). Tree heights on plots that were prepared by disk
ing and bedding averaged 32 and 46%, respectively,
greater than heights of trees in minimally prepared
plots. On the other hand, the application of CSP and
DAP fertilizers resulted in increases in tree growth of
12 and 19% respectively, over the non-fertilized trees
averaged across all site preparation treatments.
Because these poorly drained soils were quite de
ficient in available P, averaging less than 1 ppm of ex
tractable P in the A1 horizon (Table 2), it is surprising
that the early height response to P fertilizers was not
considerably greater than shown in Fig. lb. Further
more, annual height increment in the fifth year indi
cated a slight reduction in the rate of response to P, as
compared to that for the first 3 years. For example,
trees treated with CSP averaged 7 cm more annual
growth than non-fertilized trees during the first 3 years,
but they averaged only 6 cm more annual growth dur
ing the fourth and fifth years. This decrease in growth
advantage due to fertilizers may have resulted from a
gradual lowering of the water table in these wet soils,
generating a greater volume of soil for tree roots to
exploit for nutrients (Pritchett and Smith, 1972). The
magnitude of height response (main effect) to bedding
also decreased from an average of 23 cm per year dur
ing the first 3 years to 10 cm in the fifth year.
There were no significant interactions between site
preparation and fertilization treatments in this soil
group, although there was a trend toward greater re
sponse to fertilizers on the minimally prepared plots.
Soil Group C (Spodic above an argillic horizon):
The main effects of height growth responses to disking,
bedding, and P fertilization on these Ultic Haplaquods
were generally significant. The responses to bedding
varied from 0 to almost 2 m, after 5 years, and was
greatest on the most poorly drained soils of the group.
Tree heights on minimally prepared plots averaged
2.44 m compared to 3.59 m on bedded plots. The mag
nitude of the annual growth response associated with
bedding was almost the same at 5 as at 3 years, but
after 8 years the growth increases had mostly dis
appeared, indicating that the initial gains due to bed
ding were rapidly diminishing, even though trees on
bedded plots were still almost 1 m taller than those on
minimally prepared plots (Fig lc).
Average heights of trees on non-fertilized, CSP, and
DAP-treated plots were 2.61, 2.95, and 3.36 m, respec
tively, after 5 years. After 8 years, the difference in
heights between fertilized and non-fertilized trees had
increased slightly. Nitrogen (as DAP) appeared to give
an additional growth response above that obtained
from P fertilizer alone. The response of young slash

54
Soil and Crop Science Society of Florida
pine to N fertilizers applied to flatwoods soils was
previously reported (Pritchett and Smith, 1972).
Responses to DAP were somewhat larger in min
imally prepared plots than in bedded plots. For ex
ample, the increases over the non-fertilized plots av
eraged 0.85, 0.72, and 0.51 m in the chop, disk, and
bed plots, respectively. These Ultic Haplaquods were
the only soils on which it appeared that NP fertilizers
might substitute, at least in part, for intensive site
preparation.
Soil Group D (Spodic without argillic horizon):
Slash pine grown on these Typic Haplaquods re
sponded well to site preparation in the early years of
plantation establishment. Trees on bedded plots after
5 years were significantly taller than those on disked
plots (Fig. Id). However, there were no differences in
annual growth rates among the three site preparation
treatments after 8 years.
Fertilizer, particularly DAP, produced significant
growth responses during the first 3 years, but by the
fifth year annual height growth was essentially the
same for all fertilizer treatments (Table 3).
Other Responses to Treatments
The main effects of site preparation and fertiliza
tion on soil bulk density, seedling survival, foliar nutri
ent concentrations, fusiform rust incidence, and under
story biomass were determined 6 years after trees were
planted (except survival was also determined after 3
years). Most treatment effects were not significant at
this stage of stand establishment and tabular data have
not been included, in the interest of space. However,
they are available in a thesis (Flaig, E. G. 1979. Some
soil and site properties influencing the response of
slash pine to site preparation and fertilization. M.S.
Thesis, University of Florida, Gainesville), and some
trends are summarized in this section.
Surface soil (0-20 cm) bulk densities averaged 1.33,
1.25, and 1.15 g/cm3 in the chopped, disked, and
bedded plots, for the three soils tested (one Ultic and
two Typic Haplaquods). In only one Typic Haplaquocl
were differences in bulk density between the chopped
plots (1.41 g/cm3) and bedded plot (1.08 g/cm3) sta
tistically significant, after 6 years.
The percentages of planted trees surviving after 3
years were generally high and varied more among soil
groups than among treatments. Survival in soil groups
A and B tended to be better than in the Spodosols
(groups C and D), but since seedling origin, soil mois
ture conditions at time of planting, and skill and care
of the operator differed among locations, generaliza
tions are probably not meaningful. The average (main)
effects on survival of site preparations, across all soils,
were 82, 86, and 89% for chopping, disking, and bed
ding, respectively. Differences in survival associated
with P fertilizer treatments were all small and non
significant.
Most nutrient concentrations in current-year need
les differed significantly among soil groups, but, except
for P and Al, they were not significantly influenced by
treatment. For example, mean levels of N were 0.92,
0.84, 0.78, and 0.79% in tissue from group A, B, C, and
D, respectively. Concentrations of K were also higher
in the wetter soils (A and B) than in the flatwoocl soils
(C and D), but the reverse was true for P and Ca. Phos
phorus was higher in tissue from fertilized plots, as
expected, but it was not expected that Al would also
be higher in tissue from P fertilized trees than in non-
fertilized trees. For example, Al in non-fertilized and
fertilized tissues from group A plots averaged 288 and
447 ppm, while those from group B plots averaged 338
and 384 ppm. Aluminum concentrations in tissue from
group C soils averaged 398 and 438 ppm and from
group D soils, 362 and 371 ppm, respectively, for non-
fertilized and fertilized plots.
Fusiform rust incidence varied from 1 to 7% of in
fected stems at some locations to 13 to 27% at other
locations, although the correlation with soil group was
not significant. This was probably due to the great
variation in infection rate within soil groups. The
main effects of fertilization were not significant, but
the effects of the more intense preparation treatments
were significantly greater (p = 0.05) than the chop
treatment, with average values of 5.7, 9.6, and 9.3%
for chop, disk, and bed.
Total understory biomass was not significantly
affected by site preparation or fertilization, after 6
years. Apparently any early reduction in ground cover
competition as a result of site preparation had largely
disappeared by that time.
MANAGEMENT IMPLICATIONS
Site preparation by flat disking improved tree
growth over that obtained on the burn and chop plots,
on these very poorly to imperfectly drained sites. This
response apparently resulted primarily from the reduc
tion in competition from understory vegetation. Bed
ding resulted in even greater response in growth than
disking (1 to 2 m advantage after 5 years). Since the
response to bedding was greatest on group A soils
(Aquults), it is presumed that tree growth improve
ment from bedding resulted, in large part, from better
aeration in the root zone, although an increase in the
rate of N and P mineralization from organic matter
may also be a factor. It is not known at this stage of
stand development whether early growth responses to
site preparation will persist to rotation age. There are
indications that they may not, particularly on group
C and D soils. It also appears that these treatments
will have no long-term effects on bulk density or chem
ical composition of sandy soils.
The responses to CSP and DAP fertilizers were
greatest on the wet sites, particularly group A soils,
and the response did not diminish during the first 5 to
8 years. The small quantity of N applied in DAP (40
kg N/ha) resulted in a greater response than that ob
tained from P alone. The responses to fertilizers and
site preparation were generally additive, so that one
operation can not effectively be substituted for the
other, with the exception of the Ultic Haplaquods.
LITERATURE CITED
Blake, G. R. 1965. Bulk density, p. 374-390. In C. A. Black (ed.)
Method of Soil Analysis. Pt. I. Agronomy 9. Am. Soc. Agron.,
Madison, WI.
Haines, L. W., and W. L. Pritchett. 1965. The effects of site
preparation on the availability of soil nutrients and slash
pine growth. Soil Crop Sci. Soc. Florida Proc. 25:356-364.
Haines, L. W., T. E. Maki, and S. G. Sanderford. 1975. The
effects of mechanical site preparation treatments on soil
productivity and tree (Pinus taeda L. and P. elliotlii Engelm.
var elliottii) growth, p. 379-395. In B. Bernier and C. H.
Winget (ed.) Forest Soils and Forest Land Management. Laval

55
Proceedings, Volume 39, 1980
Univ. Press, Quebec.
Jackson, M. L. 1958. Soil Chemical Analysis. Prentice-Hall, Inc.,
Englewood Cliffs, N.J. 598 p.
Pritchett, W. L., and W. H. Smith. 1972. Fertilizer responses in
young pine plantations. Soil Sci. Soc. Am. Proc. 36:660-663.
Pritchett, W. L., and W. H. Smith. 1974. Management of wet
savanna soils for pine production. Florida Agr. Expt. Sta.
Bull. 762. 22 p.
Corn Response to Nitrogen and Phosphorus in a
Florida Ultisol for Simulation of Field Fertilization
Techniques Used in El Salvador1
E. Jacome and W. G. Blue2
ABSTRACT
The current fertilization technique for corn (Zea
mays L.) in El Salvador, Central America, is to apply
N at 50 kg/ha as (NH4)2S04 and P at 44 kg/ha (100
kg P205/ha) as triple superphosjriiate (TSP) under the
seed in a planting trench, with seed and fertilizer sep
arated by 2 to 3 cm of soil. Corn grain yields are rela
tively low and grain production per unit of N is ap-
proximately 11 kg/kg of applied N in contrast to more
than 30 kg of grain/kg of applied N in other areas.
Dothan fine sandy loam (fine, loamy, siliceous,
thermic Plinthic Paleudult) was used in a greenhouse
pot experiment to study the effect of banded applica
tions of N as (NH4),S04 and P as TSP under the corn
plant on its top growth, root development, and nutri
ent iqitake. The soil was limed 3 weeks before initia
tion of the experiment. Where fertilizer was applied in
a band, the band was 5 cm wide and 2 to 3 cm below
the seed. Treatments which did not receive (NH4),S04
in the band received the same amount of N as
(NH4),S04 in solution applied to the soil surface; all
treatments received K as K2S04 also applied in solution
to the soil surface. Seed germination was not affected
by application of (NH4)2S04 in combination with TSP
below the seed, but plant height, herbage weight, root
weight, and nutrient contents were less than with TSP
alone below the seed. Oven-clry herbage and root
weights 33 days after planting were reduced by 50 and
40%, respectively, by the (NH4),S04; plant height
was also reduced by 15%. This adverse effect of
(NH4)2S04 applied below the seed under nearly ideal
moisture conditions in this greenhouse experiment
could be amplified under field conditions of uncertain
rainfall. Furthermore, the magnitude of corn grain
yields in most cases under field conditions in El
Salvador would indicate that N could be omitted at
planting and applied as side dressings at appropriate
times, thus avoiding the potential for damage to young
corn.
Additional Index Words: Ammonium sulfate,
Triple superphosphate, Banded fertilizer, Zea mays L.
Corn (Zea mays L.) constitutes more than 50% of
the basic human diet in all Central American
countries; it is produced primarily by small farmers
iFlorida Agricultural Experiment Stations Journal Series No.
2280.
^Graduate student and Professor (Soil Chemistry and Fertil
ity), Soil Science Department, Institute of Food and Agricultural
Sciences, University of Florida, Gainesville, FL 32611.
(campesinos) (U. S. Economic Research Service, 1963,
1977 and Salazar, 1968). The development of technical
programs to improve existing agronomic practices,
which have been used by farmers for generations, is
common. The current production system in El Salva
dor involves preparation of land by animal traction
and the Egyptian plow (a wooden plow with metal
point). Planting trendies which are approximately 20
cm wide at the top, 5 cm wide at the bottom, and 10
to 15 cm deep are made at 80-cm intervals, also with
the Egyptian plow. If fertilizers are used, they are
applied by hand in a band at the bottom of the trench.
The fertilizer is covered by kicking a 2 to 3 cm thick
layer of soil over it. Corn seeds are placed on the soil
immediately above the fertilizer and covered with addi
tional soil. Fertilizer materials are usually (NH4)2S04
and triple superphosphate (TSP). Ammonium sulfate
is widely used because most El Salvadorean soils are
considered to be S deficient. Potassium is presently in
adequate supply in most soils, and soil pH is usually
above 5.5. Almost all corn is grown without irrigation.
Several fertilizer experiments were conducted through
out El Salvador from 1959 through 1968 (Salazar,
1968). Phosphorus at rates from 0 to 70 kg/ha (0 to
160 kg of P2Os/ha) was applied below the seed in the
previously described manner. Nitrogen was applied at
rates from 0 to 180 kg/ha. In some experiments, all of
the N was applied in the trench before planting and in
others some N was applied in the trench and some
applied as side-dressings beside the row. However, in
all experiments, treatments which included N had a
substantial amount applied below the seed.
Corn grain yields in this series of experiments were
generally low and response to N was usually in the
order of 11 kg of grain/kg of N applied. This is in
contrast to corn grain production/kg of N of 33 in
Ohio (Agronomy Dept., Ohio State Univ., 1978), and
31 to more than 40 in Florida (Rhoads and Stanley,
1979; Robertson et al., 1968).
Current experiments in El Salvador continue to
give responses similar to those reported by Salazar,
1968. The current recommendation is to apply 50 kg
of N/ha as (NH4),S04 and 44 kg of P/ha (100 kg of
P205/ha) as TSP in the trench below the seed. It has
long been known that relatively low P rates in P-
deficient soils may be more effective when the P is
placed in a band beside the seed (Nelson, 1956; Singh
and Black, 1964; and Welch et al., 1966) than when
broadcast and incorporated. However, it has also been
recognized that N in sizeable quantity placed near the
seed may be harmful because of high salt concentration
(Tisdale and Nelson, 1975). We believe the technique

56
Soil and Crop Science Society of Florida
of fertilizer placement used in El Salvador may be at
least partially responsible for low response to fertilizer
N and P.
The objective of this experiment was to compare
the growth response of corn to a fertilizer-placement
treatment similar to that used in El Salvador with
treatments where P only is applied in a band below
the seed and incorporated into the soil.
MATERIALS AND METHODS
The experiment was conducted in the greenhouse
in Gainesville, Florida, from 23 May to 27 June 1979.
The upper 15 cm of a Dothan fine sandy loam (fine,
loamy, siliceous, thermic Plinthic Paleudult) soil from
Escambia County, Florida, was used. The original soil
pH in a soihwater suspension of 1:2 was 4.1, electrical
conductivity (EC) was 1.15 mmho/cm, CEC was 8.36
meq/100 g, and ECEC was 3.04 meq/100 g. The clay
and silt contents of this soil were 8.2 and 36.7%, re
spectively, on a weight basis; mineralogy of the clay
fraction was a mixture of kaolinite, quartz intergrades,
and feldspars.
The soil was limed with 2 meq of CaCO3/100 g and
fertilized with a micronutrient frit at 15 p,g/g 3 weeks
before use in the experiment. After incubation and
drying, 2 kg of soil were placed above 650 g of small
stones in tapered plastic pots which were 15 cm wide
at the top and 15 cm high. Fertilizers were applied as
shown in Table 1. Treatment 4 represented the com
mon fertilization practice in El Salvador. In El
Salvador, corn is planted in 80-cm rows; this gives
12,500 m of row/ha. It is currently recommended that
(NH4)2S04 and TSP be banded beneath the seed at
rates of 50 kg of N and 44 kg of P/ha (100 kg of
P205/ha). Fertilizer materials are applied in a band
approximately 5 cm wide, so that they are equivalent
to 1 g of (NH4)2S04 and 0.9 g of TSP per 5 cm of row.
The amount of fertilizer applied per pot was based on
the previously described relationships and 15-cm diam
eter of the pots. In those treatments which received the
same amount of nutrient incorporated, soil and fertil
izers were mixed thoroughly in plastic bags before
placement in pots.
All pots received a uniform application of K,S04
in solution, at a rate of 200 pg/g of soil. Treatments
1, 2, and 3 received (NH4)2S4 in solution at a rate of
300 pg/g based on soil weight; this was the same quan
tity of N that was applied to Treatment 4. Both K2S04
TABLE 1.Fertilization materials and techinques on a Florida
Ultisol for simulation of field treatments used in El Salva
dor.
Treatmentsf
Fertilizer nutrients
N
p
N
(nh4)2so4
P25
TSP
kg/ha
g/5 cm row
kg/ha
g/5 cm row
1
50
0
0
0
2
50
0
100
0.9
3
50
0
100
Incorporated
4
50
1
100
0.9
(Treatments 1 through 3 received N as (NH4)2S04 in solution
equivalent to that applied to Treatment 4. All treatments received
K as KS04 equivalent to 200 pg/g of soil.
and (NH4),S04 were applied to the soil surface in two
applications, one half at emergence of seedlings and
one half 10 days after emergence.
Corn (variety Dekalb XL-395) was used in the ex
periment; germination observations, plant growth
measurements, and chemical determination of nutri
ents in plant tissue were made. Soil samples were ob
tained by inserting a tube through the fertilizer band
which corresponded to the plant row.
A randomized block design with four replications
was used. The data were analyzed statistically by
analyses of variance; treatment means were compared
by Duncans new multiple range test.
RESULTS AND DISCUSSION
Corn seed germination was not significantly re
duced by any of the treatments (Table 2). Plant heights
at 9, 14, and 33 days after emergence were adversely
affected by (NH4)2SO, under the seed in addition to
the P (Treatment 4). At 33 days, plant height from
Treatment 1 was severely depressed by P deficiency
and plant height from Treatment 4 remained signif
icantly less than from Treatments 2 and 3 with P only
banded under the seed or with P incorporated. Corn
herbage weights 33 days after germination were dras
tically affected by treatments; herbage weight from
Treatment 1 without P was only 1.0 g/pot and from
Treatment 4 with N and P applied under the seed
11.9 g/pot compared with 19.5 g/pot from Treatment
2 with P alone under the seed. Plant height of Treat
ment 4 at the same age was 102 cm, 15% less than 121
and 117 cm for Treatments 2 and 3. Plant root systems
were affected in a manner similar to herbage. The
root system from Treatment 1 without P was only 0.2
g/pot; that from Treatment 4 with N and P under the
seed was 1.9 g/pot while that from Treatment 2 with
P only under the seed was 4.3 g/pot (Table 2). The
smaller root system from Treatment 4 was undoubtedly
a consequence of the high salt concentration immedi
ately below the plants in the early growth stage. It is
likely that this restriction of root growth in young
plants may result in a more shallow, less developed
root system which will restrict water and nutrient up
take from subsoils.
Robertson and Hutton (1959) and Mengel and
Barber (1974) held that the deeper the root system, the
better the plant is able to withstand periods of mois
ture stress. Root system development is particularly
important in the Central American countries, where
most producers depend only on rainfall; a well de
veloped root system is essential to explore deeper parts
TABLE 2.Corn growth response to fertilizer rates and place
ment on a Florida Ultisol.
Treat- Germi- Days after planting Oven-dry weights
ments
nation
9
14
33
Herbage
Roots
.. Plant height,
cm ..
g/pot
1
95a*
5 a
30 a
43 c
1.0 c
0.2 c
2
100 a
4 a
38 a
121 a
19.5 a
4.3 a
3
90 a
4 ab
33 a
117 a
18.2 a
3.8 a
4
95 a
3b
21 b
102 b
11.9 b
1.9 b
Values within
columns
followed by the
same letter
do not
differ significantly at the 0.05 level of probability according to
Duncans new multiple range test.

57
Proceedings, Volume 39, 1980
of the soil where moisture is retained if high grain
yields are to be produced.
Herbage nutrient concentrations were generally
adequate for plant growth (Table 3); except for P,
nutrient concentrations were inversely related to top
growth. Herbage concentrations of P and K from
Treatment 4 were significantly larger than from Treat
ments 2 and 3. Calcium, Mg, and Cu concentrations
were low for all treatments except 1 where growth was
poor because of P deficiency. Concentrations of Fe, Mn,
and Zn were adequate for plant growth in Treatments
2, 3, and 4; however, they were unusually high for
plants from Treatment 1. With the exception of Fe,
Cu, and Zn, nutrient contents were significantly re
duced for Treatment 4 as compared with 2 and 3
(Table 4). The only difference between Treatments 2
and 3, and 4 was the manner of N application. In
Treatment 4, N was applied prior to seeding in a band
only 2 to 3 cm below the seed; therefore, the reduction
of plant growth from Treatment 4 was likely caused by
the high concentration of (NH4)2SOf in the 5-cm wide
application band.
Root nutrient concentrations were relatively un
predictable, probably because of analytical error asso
ciated with small sample size; therefore, these data are
not presented. However, because of smaller root mass,
root nutrient contents from Treatment 4 were lower
than from Treatments 2 and 3.
Values for EC (Table 5) in the soil ranged from
5.8 to 6.4 mmho/cm for Treatments 2, 3, and 4. For
Treatment 1, EC was significantly higher probably be
cause of poor plant growth and low nutrient uptake as
a consequence of severe P deficiency. High concentra
tions of K in the soil and N in the foliage support this
statement.
Although soil pH was lower than that intended,
the appearance of plants in Treatments 2, 3, and 4
showed no evidence of A1 toxicity. Even though pH
TABLE 5.Soil pH, electrical conductivity, and double-acid
EXTRACTABLE NUTRIENTS IN SOIL AFTER FERTILIZATION AND CROPlING.
Double-acid
Treat- extractable nutrients
ments
pH
ECf
P
K
Ca
Mg
mmho/cm
ppm ...
1
4.8 a*
10.7 a
3c
193 a
261 c
180 a
2
4.1 c
6.0 b
68 b
84 b
504 ab
120 a
3
4.1 c
5.8 b
55 b
19c
428 b
166 a
4
4.3 b
6.4 b
186 a
46 c
605 a
146 a
fEC of the virgin soil was 1.2 mmho/cm.
Values within columns followed by the same letter do not
differ significantly at 0.05 level of probability according to
Duncans new multiple range test.
values were low, A1 saturation of the ECEC (Table 6)
was substantially below the 44% level mentioned by
Kamprath (1970) for normal growth of corn. Further
more, corn responded to lime in mineral soils only
when A1 saturation of the ECEC was above 70%, at
which point concentration of soil solution A1 increased
sharply (Evans and Kamprath, 1970). In Treatments 2
and 3, with large root systems, exchangeable A1 was 1.6
and 1.7 meq/100 g of soil, respectively, with percentage
saturations of the ECEC of 28 and 31. In contrast, the
root system from Treatment 4 with (NHJ),SO,1 applied
below the seed was relatively small; exchangeable A1
in soil from Treatment 4 was 0.9 meq/100 g which
represented a percentage saturation of the ECEC of
only 18. Phosphorus in the soil after cropping was
significantly higher in Treatment 4 than in soils from
Treatments 2 and 3, probably because of smaller root
and herbage nutrient contents.
We think that this adverse effect of (NH4)2S04 ap
plied below the seed under nearly ideal moisture con
ditions in this greenhouse experiment could be ampli-
TABLE 3.Corn herbage nutrient concentrations.
Oven-dry herbage nutrients
Treatments
Nf
P
K
Ca
Mg
Fe
Mn
Cu
Zn
%
1
5.03
0.09 c*
3.19 a
0.31 a
0.47 a
179 ab
151 a
8 a
228 a
2
2.95
0.21 b
1.50 c
0.15 c
0.22 b
92 b
41 b
2b
23 b
3
2.83
0.21 b
1.75 c
0.17 b
0.22 b
116 b
41 b
4b
25 b
4
3.31
0.29 a
2.50 b
0.14 d
0.21 b
209 a
39 b
3b
30 b
fNitrogen was determined in samples composited from all replications.
Values within columns followed by the same letter do not differ significantly at 0.05 level of probability according to Duncans new
multiple range test.
TABLE 4.Corn herbage nutrient contents.
Herbage nutrients
Treatments N P K Ca Mg Fe Mn Cu Zn
mg/pot
1
50
0.9 d*
31.9 d
3.1 d
4.7 d
0.2 b
0.2 d
0.008 b
0.228 b
2
573
40.6 a
290.3 b
29.6 b
43.7 a
1.8 a
0.8 a
0.046 a
0.439 a
3
515
37.4 b
315.5 a
30.1 a
39.5 b
2.1 a
0.7 b
0.067 a
0.451 a
4
394
32.9 c
279.5 c
16.1 c
16.0 c
2.6 a
0.5 c
0.035 ab
0.350 a
Values within columns followed by the same letter do not differ significantly at the 0.05 level of probability according to Duncans
new multiple range test.

58
Soil and Crop Science Society of Florida
TABLE 6.Exchangeable cations and ECEC for soil after fer
tilization AND CROPPING.
A1
Treat- Exchangeable cationsf satn-
ments
Al
H
Ca
Mg
ECEC
ration
%
1
0.7 b*
0.8 a
LI d
1.4 a
3.9 b
18
2
1.6 a
0.8 a
2.2 b
0.9 b
5.6 a
28
3
1.7 a
0.8 a
1.8 c
1.2 ab
5.4 a
31
4
0.9 b
0.6 a
2.6 a
1.1 ab
5.1 a
18
fThe values for the virgin soil were 0.57, 0.40, 1.01, 1.03, and
3.0 for exchangeable Al, H, Ca, Mg, and ECEC, respectively.
Values within columns followed by the same letter do not
differ significantly at the 0.05 level of probability according to
Duncans new multiple range test.
fied under field conditions of uncertain rainfall.
Furthermore, the magnitude of corn yield in most cases
under field conditions in El Salvador would indicate
that N could be omitted at planting and applied as
side dressings at appropriate times, thus avoiding the
potential for damage to young corn.
LITERATURE CITED
Agronomy Department, Ohio State University. 1978. Soil fertility
research report. Series No. 219. Ohio State University, Colum
bus, Ohio.
Evans, C. E., and E. J. Kamprath. 1970. Lime response as related
to percentage A1 saturation, solution Al, and organic matter
content. Soil Sci. Soc. Am. Proc. 34:893-896.
Kamprath, E. J. 1970. Exchangeable aluminum as a criterion for
liming leached mineral soils. Soil Sci. Soc. Am. Proc. 34:252-
254.
Mengel, D. B and S. A. Barber. 1974. Development and distribu
tion of the corn root system under field conditions. Agron. J.
66:342-344.
Nelson, L. B. 1956. The mineral nutrition of corn as related to
its growth and culture. Adv. Agron. 8:321-375.
Robertson, W. K., and C. E. Hutton. 1959. Fertilizer placement
studies on farm crops. Soil and Crop Sci. Soc. Florida Proc.
19:190-196.
Robertson, W. K., L. G. Thompson, Jr., and L. C. Hammond.
1968. Yield and nutrient removal by corn (Zea mays L.) for
grain as influenced by fertilizer, plant population, and hybrid.
Soil Sci. Soc. Am. Proc. 32:245-249.
Rhoads, F. M., and R. L. Stanley. 1979. Effect of population and
fertility on nutrient uptake and yield components of irrigated
corn. Soil and Crop Sci. Soc. Florida Proc. 38:78-81.
Salazar, R. J. 1968. Estudio de fertilizacin en maiz, Ministerio
de Agricultura y Ganadera. El Salvador. Boletn Tcnico No.
50.
Sanchez, P. A. 1976. Properties and management of soils in the
tropics. A. Wiley-Interscience Publication, New York, N. Y.
Singh, R. M., and C. A. Black. 1964. Test of the DeWit compen
sation function for estimating the value of different fertilizer
placement. Agron. J. 56:572-574.
Tisdale, S. L., and W. L. Nelson. 1975. Soil Fertility and Fertil
izers. 3rd Edition. MacMillan Publishing Co., Inc., New York.
U. S. Economic Research Service. 1963. El Salvador, Its agricul
ture and trade. USDA. 49:18-22.
U. S. Economic Research Service. 1977. Foreign Agricultural Eco
nomic Report. USDA. 135:12-13.
Welch, L. F., D. L. Mulvaney, L. V. Boone, G. E. McKibben,
and J. W. Pendleton. 1966. Relative efficiency of broadcast vs.
banded phosphorus for corn. Agron. J. 58:283-287.
Growth and Cadmium Uptake by Lettuce and Radish
Fertilized with Cadmium, Zinc, and Sewage Sludge1
Charles C. Hortenstine2
ABSTRACT
A complete factorial experiment with two levels of
sewage sludge (0 and 100 metric tons/ha), three levels
of Zn (0, 50, and 100 kg/ha), and three levels of Cd
(0, 2.5, and 5.0 kg/ha) mixed throughout the soil was
conducted in the greenhouse with Arredondo fine sand
(loamy, siliceous, hyperthermic Grossarenic Paleudalf).
Indicator plant species were leaf lettuce (Lactuca sativa
L. var. crispa cultivar Grand Rapids) harvested at 8
weeks from planting followed by radish (Raphanus
sativus L. cultivar Red Globe) harvested at 6 weeks
from planting. Yields of lettuce were significantly in
creased by the sludge, but significantly decreased by
the highest rate of Zn and Cd. Water-soaked spots
which gradually coalesced with time to produce dead
tissue were prevalent on lettuce leaves in the highest
rate of Zn on soil with no sludge. These spots were
symptoms of Zn phytotoxicity which were not mani
fested in sludge treated soil. In contrast to lettuce,
yields of radish tops and roots were significantly less in
sludge treated soil as compared to soil which had re
1 Florida Agricultural Experiment Stations Journal Series No.
2281.
2Professor of Soil Chemistry, Soil Science Department, Uni
versity of Florida, Gainesville, FL 32611.
ceived no sludge. No visible symptoms of phytotoxicity
were produced in radish plants by any treatment.
Additional Index Words: Grossarenic Paleudalf,
Phytotoxicity, Lactuca sativa, Raphanus sativus.
The utilization of municipal sewage sludge (SS) as
a soil amendment or source of plant nutrients has in
creased substantially during the past several years in
the United States. Potential hazards exist when SS
containing relatively high levels of heavy metals is
applied to agricultural soils with subsequent entry of
these metals into the human food chain. Cadmium is
especially important in this respect as it can accumu
late within various body organs in amounts that can
produce disease or fatalities (Shroeder, 1965; Axelsson
and Pascator, 1966; Carroll, 1966). The incidence of
itai-itai disease in the Jintsu basin of Japan during
the 1960s focused worldwide attention on the accumu
lative effects of Cd in the diet (Tsuchiya, 1969). Jap
anese health officials (Yamegata and Shigematsu, 1970)
determined that rice was the major dietary source of
Cd in that epidemic and that the locally produced rice
contained over 1.0 ¡xg Cd/g with a range up to 3.4 p,g
Cd/g. They further stated that a daily intake of 300 ¡xg

59
Proceedings, Volume 39, 1980
Cd/person was the maximum acceptable and that 0.4
¡j.g Cd/g was the upper limit in unhulled rice.
Sludge applications to soils used for the production
of human foods are controlled to a large extent by
guidelines as set forth by the USEPA, Solid Wastes
Disposal Facilities (1978). Among the criteria proposed
by EPA are that soil pEl be at or above 6.5, total
amounts of Cd added not exceed 10 g Cd/g soil, and
that SS containing in excess of 20 mg Cd/kg would not
be permitted where certain crops are grown, i.e., leafy
vegetables that absorb relatively large amounts of Cd.
Several soil factors are known to affect Cd availabil
ity for plant uptake; among these are Zn and organic
matter (Haghiri, 1974; Maclean, 1976). The objectives
of this study were to evaluate the main effects and
interactions of Cd, Zn, and SS with a low Cd content
on the growth and Cd uptake of leaf lettuce (Lactuca
sativa L var. crispa cultivar Grand Rapids) and radish
(Raphanus sativus L. cultivar Red Globe) in Ar
redondo fine sand (loamy, siliceous, hyperthermic
Grossarenic Paleudalf).
MATERIALS AND METHODS
Arredondo fine sand, obtained from the 0 to 15-cm
depth of an uncultivated area, was air-dried and seived
to remove plant debris and small rocks. The soil was
limed with reagent grade CaC03 to pH 6.5, from an
original pH 5.9, and weighed at 2,700 g soil/pot into
plastic pots lined with polyethylene bags. The experi
mental design was a 2 x 3 x 3 factorial with two levels
of SS (0 and 100 tons/ha), three levels of Cd as CclCl2
(0, 2.5, and 5.0 kg/ha), and three levels of Zn as ZnS04
(0, 50, and fOO kg/ha) replicated four times. In addi
tion, Ca(N03)2, KH2P04, KC1, MgNOs, MnS04,
CuS04 and H3B03 reagent grade compounds were
added to each pot in sufficient amounts to assure op
timum plant growth. All plant nutrients and soil
amendments were mixed with the soil from individual
pots in a twin-shell blender. The pots were arranged on
greenhouse benches in randomized blocks and allowed
to incubate for 2 weeks before planting day. Ten
lettuce seeds were planted, and the seedlings were later
thinned to three in each pot. Soil moisture was main
tained with distilled water at about 10% by weighing
the pots at 2 to 3-day intervals. After 8 weeks from
planting, the lettuce roots and tops were removed,
washed in distilled water, dried at 70 C, weighed, and
ground in a stainless steel Wiley mill before chemical
analyses. The same amounts of N-P-K were added to
each pot as for the lettuce and 10 radish seeds were
planted. Radish seedlings were thinned to six per pot
and harvested at 6 weeks from planting date. Radish
tops and roots were prepared for analyses the same as
for the lettuce plants.
Plant tissue was ashed at 450 C for 8 hours, dis
solved in 6N HC1, made to volume with distilled,
deionized water, and analyzed by atomic absorption for
Cd. Soil samples were removed from the pots after the
radish harvest, and extracted in 0.005M diethylene-
pentaacetic acid + 0.1M triethyleneamine (DTPA) ac
cording to the method proposed by Lindsay (1972),
and analyzed by atomic absorption for Cd. Total solu
ble salts (TSS) were estimated by electrical conductance
(EC) in a saturated soil extract (USDA Handbook No.
60, 1954).
RESULTS AND DISCUSSION
Lettuce
Seed germination and seedling growth were normal
in all pots in spite of relatively high TSS in some of
the SS treated pots (discussed under Soil section).
During the second and third weeks of growth, all of
the lettuce plants in pots that had received 100 kg
Zn/ha and no SS began to develop small, water-soaked
spots which grew in size with time until a large part
of the leaves was affected. These areas gradually dried
and the affected tissue died. During the latter part of
the growth period (4 to 5 weeks), lettuce in the 50 kg
Zn/ha pots began to show the same phytotoxic effects.
This phytotoxicity was no doubt caused by the added
Zn which was, in some way, rendered non-toxic by the
addition of SS to the soil. Lettuce in SS treated pots
was also greener and appeared to be in much better
physical condition than lettuce in the pots with no SS.
Lettuce leaf yields (Table 1) increased with SS and
decreased with Cd additions to pots with no SS. The
severe phytotoxic effects produced by Zn when no SS
was added had no significant affect on yield. There
were significant SS x Cd and Cd x Zn interactions. The
yields of lettuce roots were comparable in magnitude to
the tops and are not presented.
Cadmium uptake by the lettuce leaves (Table 2)
was drastically increased by Cd additions to the soil,
but this increase was ameliorated considerably by the
addition of SS. The interactions displayed in Table 2
are quite interesting. Zinc applied to the no SS treat
ments apparently decreased Cd uptake, but increased
Cd uptake for SS-treated soil. Since lettuce leaves are
not a major item in human diets, Cd uptake of the
magnitude shown in this study should not be viewed
as a health hazard.
The Cd contents of lettuce roots (Table 3) were
increased significantly by Cd additions to the soil, but
the increases were not of the magnitude as shown by
the lettuce leaves. Sludge and Zn additions had no
effect on Cd uptake by the roots. However, there was a
SS x Zn interaction manifested by a decrease in Cd
uptake with Zn applied to no SS pots and an increase
in Cd uptake where Zn was applied to SS pots.
TABLE 1.Influence of Cd, SS, and Zn on dry matter yield of
LETTUCE.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
O
O
(
Avg
0
0
2.0
2.0
1.7
1.9
2.5
0
1.3
1.4
1.0
1.2
5.0
0
1.0
1.8
1.4
1.4
Avg
1.4
1.7
1.4
1.5
0
100
2.3
1.5
1.4
1.5
2.5
100
2.2
2.3
1.6
1.5
5.0
100
2.1
1.8
I.G
1.9
Avg
2.2
1.9
1.7
2.0
Significant differences:
P < 0.001-SS, SS x Cd.
P < 0.01Cd, Cd x Zn.

60 Soil and CRor Science Society of Florida
TABLE 2.Cadmium contents of lettuce tops crown in ar- TABLE 4.Influence of Cd, Zn, and SS on dry matter yield of
REDONDO FINE SAND. RADISH TOPS.
Cd added SS added Zn added, kg/ha
kg/ha tons/ha 0 50 100 Avg
0
2.5
5.0
0
0
0
2.3
54.7
82.7
1.1
32.3
57.7
1.6
31.8
47.4
1.7
39.6
62.6
Avg
46.7
30.4
26.9
34.7
0
100
2.3
5.6
5.7
4.5
2.5
100
18.6
18.9
33.6
23.7
5.0
100
37.1
50.8
47.5
45.1
Avg
19.3
25.1
28.9
24.4
Significant differences:
P < 0.001Cd, SS, SS x Cd, Cd x Zn, SS x Cd x Zn.
Radish
Radish top weights were decreased by the addition
of SS to the soil (Table 4) and there was a SS x Zn
interaction. Germination and plant growth were
normal in all pots and there were no symptoms of
phytotoxicity produced in any of the radish plants. It
is noteworthy that SS caused about a 25% decrease in
radish top weights, whereas it caused an increase of
about the same amount in lettuce weights.
Cadmium contents of radish tops (Table 5) were
increased by Cd additions and decreased by Zn addi
tions to the no SS treatments. All interactions tested
were significant except for the SS x Cd interaction.
Cadmium uptake by the radish tops was not as great
as in the lettuce leaves (20 vs 30 fig/g overall averages),
but this may have resulted from the longer growing
period for lettuce (8 vs 6 weeks). However, Turner
(1973) found differences of the same magnitude be
tween lettuce (24 fig Cd/g) and radish tops (15 ¡ig
Cd/g) harvested after 5 weeks in solution containing
0.10 ¡ig Cd/ml.
TABLE 3.Cadmium contents of lettuce roots grown in ar
redondo FINE SAND.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
100
Avg
Zig/g
0
0
1.3
0.7
0.5
0.8
2.5
0
15.6
8.4
10.9
11.6
5.0
0
22.2
19.7
16.1
19.3
Avg
13.0
9.6
9.2
10.6
0
100
2.3
3.1
4.4
3.3
2.5
100
8.8
13.3
13.5
11.9
5.0
100
16.8
15.7
20.8
17.8
' Avg
9.3
10.7
12.9
11.0
Significant differences:
P < 0.001Cd, SS x Zn.
P < 0.05SS x Cd x Zn.
Cd added
kg/ha
SS added
tons/ha
0
Zn added, kg/ha
50 100
Avg
0
0
2.2
2.3
g/pot
2.2
2.2
2.5
0
2.2
2.3
2.2
2.2
5.0
0
2.0
2.5
2.2
2.2
Avg
2.1
2.4
2.2
2.2
0
100
1.7
1.8
1.5
1.7
2.5
100
1.8
1.6
1.4
1.6
5.0
100
1.7
1.8
1.5
1.7
Avg
1.7
1.7
1.5
1.6
Significant differences:
P < 0.001-SS.
P < 0.01SS x Zn.
P < 0.05Zn.
Radish root weights were decreased by SS and Zn
application at the highest rate (Table 6) and there was
a significant SS x Zn interaction. There was about 41 %
reduction in oven-dry weight of radish roots and a cor
responding 47% reduction in fresh weight (from 48
g/pot to 26 g/pot) from the addition of SS. However,
dry matter in the roots was increased from 6.6 to 7.8%
by the addition of SS. It is postulated that TSS in the
SS treated soil caused the reduction in radish top and
root yields (a further discussion of this follows in the
Soil section).
The radish roots (Table 7) contained about 20%
of the level of Cd contained in the lettuce roots (2.1
vs 10.8 ¡xg/g). It is highly unlikely that Cd toxicity
from radish with Cd levels would pose a problem in
the human diet.
Soil
The Arredondo fine sand used in this study had pH
5.9 in water and contained 5.9 ¡ig P/g, 24 ¡xg K/g, 24
fig Ca/g, and 92 fig Mg/g extracted in IN NH.jOAc
(pH 4.8). The SS was obtained from the Walt Disney
TABLE 5.Cadmium contents of radish tops grown in ar
redondo FINE SAND.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
100
Avg
ZZg/g
0
0
2.2
0.8
1.0
1.3
2.5
0
34.5
17.2
17.4
23.0
5.0
0
55.5
34.7
31.6
40.6
Avg
30.7
17.6
10.9
19.7
0
100
1.7
2.7
3.0
2.5
2.5
100
18.3
24.1
21.8
21.4
5.0
100
40.3
34.5
36.8
37.2
Avg
20.7
20.4
20.5
20.5
Significant differences:
P < 0.001Cd, Zn, SS x Zn, Cd x Zn, SS x Cd x Zn.

Proceedings, Volume 39, 1980
TABLE 6.Influence of Cd, SS, and Zn on dry matter yield of
RADISH ROOTS.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
100
Avg
0
0
3.2
3.2
2.9
3.1
2.5
0
3.5
3.1
3.3
3.3
5.0
0
2.9
3.4
3.1
3.1
Avg
3.2
3.2
3.1
3.2
0
100
2.1
2.2
1.7
2.0
2.5
100
2.3
1.8
1.3
1.8
5.0
100
2.0
2.3
1.8
2.0
Avg
2.1
2.1
1.6
1.9
Significant differences:
P < 0.001-SS.
P < 0.01Zn.
P < 0.05SS x Zn.
World sewage treatment plant and it measured pH
5.4 in water and contained total amounts of 60/Xg P/g,
500 /j.g K/g, 2,500 fig Ca/g, and 3,300 fig Mg/g. The
EC was 6.56 mmhos/cm which indicated a TSS content
that would restrict yields of most food crops (USDA
Handbook No. 60, 1954). The SS produced at Walt
Disney World is entirely from human activity and con
tains no industrial component. The DTPA-extractable
Cd in this SS was 2.7 jug/g and the Zn was 151 fig/g,
both of which are quite low values as compared to
other municipal SS (Chicago SS used in another of my
studies contained 25 fig Cd/g and 925 ¡xg Zn/g).
The Cd content of Arredondo fine sand at the end
of 16 weeks and after two harvests (Table 8) indicated
a large increase from Cd applications with no signif
icant effect from SS application. Evidently, the small
amount of Cd in the SS was not enough to effect a
change in soil Cda total of 270 g Ccl/ha was added by
the 100 tons/ha rate of SS. However, there was a sig
nificant SS x Cd interaction.
Total soluble salts were more than doubled by SS
TABLE 7.Cadmium contents of radish roots crown in ar
redondo FINE SAND.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
100
Avg
0
0
0.3
0.3
0.3
0.3
2.5
0
4.0
1.6
1.4
2.3
5.0
0
7.2
3.9
2.7
4.6
Avg
1
3.9
1.9
1.5
2.4
0
100
0.9
0.5
0.4
0.4
2.5
100
1.5
1.7
1.7
1.6
5.0
100
3.2
3.6
3.2
3.3
Avg
1.8
1.9
1.8
1.8
Significant differences:
P < 0.001Cd, SS, Zn, SS x Cd, SS x Zn, Cd x Zn, SS x Cd
x Zn.
61
TABLE 8.Cadmium contents of arredondo fine sand extracted
IN DTPA at the end of experimental period OF 16 WEEKS.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
100
Avg
0
0
0.06
0.09
0.06
0.07
2.5
0
1.17
1.56
1.26
1.26
5.0
0
2.54
2.68
2.68
2.63
Avg
1.26
1.38
1.33
1.32
0
100
0.24
0.29
0.24
0.26
2.5
100
1.20
1.22
1.24
1.22
5.0
100
2.26
2.43
2.36
.2.35
Avg
1.23
1.31
1.28
1.28
Significant differences:
" P< 0.001-Cd, SS x Cd.
P < 0.05Zn.
TABLE 9.Total soluble salts in arredondo fine sand at the
END OF THE EXPERIMENTAL PERIOD OF 16 WEEKS.
Cd added
SS added
Zn added, kg/ha
kg/ha
tons/ha
0
50
100
Avg
hos/rm
0
0
1.45
1.21
1.58
1.41
2.5
0
1.21
1.50
1.11
1.27
5.0
0
1.50
1.07
1.16
1.24
Avg
1.39
1.26
1.28
1.31
0
100
2.95
2.66
3.29
2.97
2.5
100
2.17
3.00
3.24
2.80
5.0
100
2.83
2.59
2.87
2.76
Avg
2.65
2.75
3.13
2.85
Significant diffe