Group Title: Bulletin University of Florida. Agricultural Experiment Station
Title: Sulfur requirement of soils for clover grass pastures in relation to fertilizer phosphates
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Permanent Link: http://ufdc.ufl.edu/UF00026453/00001
 Material Information
Title: Sulfur requirement of soils for clover grass pastures in relation to fertilizer phosphates
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 32 p. : ill. ; 23 cm.
Language: English
Creator: Neller, J. R ( Joseph Robert ), 1891-
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1951
Copyright Date: 1951
 Subjects
Subject: Clover -- Soils -- Florida   ( lcsh )
Grasses -- Soils -- Florida   ( lcsh )
Soils -- Sulphur content -- Florida   ( lcsh )
Phosphatic fertilizers -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 31-32).
Statement of Responsibility: J.R. Neller ... et al..
General Note: Cover title.
 Record Information
Bibliographic ID: UF00026453
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltuf - AEN6385
oclc - 18264944
alephbibnum - 000925729

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Copyright 2005, Board of Trustees, University
of Florida









BULLETIN 475 APRIL 1951
UNIVERSITY OF FLORIDA ) N
AGRICULTURAL EXPERIMENT STATION
WILLARD M. FIFIELD, Director
GAINESVILLE, FLORIDA


Sulfur Requirement of Soils For Clover-

Grass Pastures in Relation to

Fertilizer Phosphates

By
J. R. NELLER, G. B. KILLINGER, D. W. JONES, R. W. BLEDSOE
AND H. W. LUNDY

TECHNICAL BULLETIN

Fig. 1.-General view of White clover-Pensacola Bahia grass plots on
Rutlege fine sand, January 8, 1948. Alleys have been cut out around
plots preparatory to clipping for yields. Plots showing clover are those
where a source of sulfur was included in the fertilizer such as gypsum
associated with superphosphate and added to rock phosphate and to
calcined phosphate. For details see Figs. 2 and 3. Background shows
growth of native wire grass, sedges and scattering pine similar to that
originally on the plot area.



S~~L""F






-


Y> 7 I f' BOARD OF CONTROL EDITORIAL
J. Francis Cooper, M.S.A., Editors
/ /- $5 Frank M. Harris, Chairman, St. Peters- Clyde Beale, A.B.J., Associate Editor'
burg L. Odell Griffith, B.A.J., Asst. Editor'
N. B. Jordan, Quincy J. N. Joiner, B.S.A., Assistant Editors '
Hollis Rinehart, Miami
Eli H. Fink, Jacksonville ENTOMOLOGY
George J. White, Sr., Mount Dora A N. Tissot, Ph.D., Entomologist
W. F. Powers, Secretary, Tallahassee L. C. Kitert, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant
EXECUTIVE STAFF F. A. Robinson, M.S., Asst. Apiculturist
J. Hillis Miller, Ph.D., Presidents RoinnM Asst A
J. Wayne Reitz, Ph.D., Provost for Agr.s HOME ECONOMICS
Willard M. Fifield, M.S., Director Ouida D. Abbott, Ph.D. Home Econ.'
J. R. Beckenbach, Ph.D., Asso. Director RB French, Ph.D., Biochemist
L. 0. Gratz, Ph.D., Asst. Dir., Research
Geo. F. Baughman, M.S., Business Mgr.s HORTICULTURE
Rogers L. Bartley, B.S., Admin. Mgr.3 TICUL
Claranelle Alderman, Accountants G. H. Blackmon, M.S.A., Horticulturist'
F. S. Jamison, Ph.D., Horticulturist'
MAIN STATION, GAINESVILLE Albert P. Lorz, Ph.D., Horticulturist
H. M. Reed, B.S., Chem., Veg. Processing
AGRICULTURAL ECONOMICS R. K. Showalter, M.S., Asso. Hort.
R. A. Dennison, Ph.D., Asso. Hort.
H. G. Hamilton, Ph.D., Agr. Econo- R. H. Sharpe, M.S., Asso. Horticulturist
mist' s F. S. Lagasse, Ph.D., Asso. Hort.2
R. E. L. Greene, Ph.D., Agr. Economist R. D. Dickey, M.S.A., Asst. Hort.
Zach Savage, M.S.A., Associate L. H. Halsey, M.S.A., Asst. Hort.
A.. H. Spuriock, M.S.A., Associate C. D. Hall, Ph.D., Asst. Horticulturist
D. E. Alleger, M.S., Associate S. E. McFadden, Ph.D., Asst. Hort.
D. L. Brooke, M.S.A., Associate Austin Griffiths, Jr., B.S., Asst. Hort.
M. R. Godwin, Ph.D., Associate
H. W. Little, M.S., Assistant' LIBRARY
Tallmadge Bergen, B.S., Assistant Ida Keeling Cresap, Librarian
D. C. Kimmel, Ph.D., Assistant
A. L. Larson, Ph.D., Agr. Economist PLANT PATHOLOGY
Orlando, Florida (Cooperative USDA) W. B. Tisdale, Ph.D., Plant Patholo-
G.Norman Rose, B.S., Asso. Agr. gist''
SEconomiAst Phares Decker, Ph.D., Plant Pathologist
S. s. Town end, J ., S.A., Agr. Erdman West, M.S., Mycologist and
Statistician' Botanist
J. B. Owens, B.S.A Agr. Statistician Robert W. Earhart, Ph.D., Plant Path.2
ENINE ING Howard N. Miller, Ph.D., Asso. Plant
.AGttlC(iJIT!TUt 'I, ENGINEERING Path.
r!.'m A. A_,r Enginerr' Lillian E. Arnold, M.S., Asst. Botanist
J. t ..... AC E. A--,:. Agr Ei,.'. C. W. Anderson, Ph.D., Asst. Plant Path.
J. M. Myer B S. Ago,. Agi. Erngri$n r
R. E. Choai. B A E A.4 Agr. r.Engs POULTRY HUSBANDRY
A. M. PEt[l- B A.E. A.-t Age. Eng N. R. Mehrhof, M.Agr., Poultry Hush.'
J. C. Driggers, Ph.D., Asso. Poultry
AGRONOMY Husb.
Fred. H. Hull, Ph.D., Agronomist' SOILS
G. B. Killinger, Ph.D., Agronomist'
H. C. Harris, Ph.D., Agronomist F. B. Smith, Ph.D., Microbiologist '
R. W. Bledsoe, Ph.D., Agronomist Gaylord M. Volk, Ph.D., Chemist
W. A. Carver, Ph.D., Associate J. R. Henderson, M.S.A., Soil Technolo-
Darrel D. Morey, Ph.D., Associate gist'
Fred A. Clark, B.S., Assistant J. R. Neller, Ph.D., Soils Chemist
Myron C. Grennell, B.S.A.E., Assistant Nathan Gammon, Jr., Ph.D., Soils
E. S. Horner, Ph.D., Assistant Chemist
A. T. Wallace, Ph.D., Assistant R. A. Carrigan, Ph.D., Biochemist'
D. E. McCloud, Ph.D.. Assistant Ralph G. Leighty, B.S., Asso. Soil
Surveyor3
ANIMAL HUSB. AND NUTRITION G. D. Thornton, Ph.D., Asso.*
T. J. Cnh. Ph Hus Microbiologist
T. J. C ba. c D. Ah Husb. I Charles F. Eno, Ph.D., Asst. Soils
R. S. C.la cscock, Ph D, An. Husb.' Microbiologist
G. K. Davis, Ph.D., Animal Nutritionist H. W. Winsor, B.S A Assistant Chemist
"R. L. Shirley, Ph.D., Biochemist' R. E. Caldwell, M S. A Asst. Chemist'
J. E. Pace, M.S.. Asst. An. Husb. V. W. Carlisle, B.S., Asst. Soil Surveyor
S. John Folks, B.S.A., Asst. An. Husb. James H. Walker, M.S.A., Asst. Soil
Katherine Boney, B.S., Asst. Chem. Surveyor
James M. Wing, M.S., Asst. Dairy Husb. N. Edson, M. S., Asst. Microbiologist
A. M Pearson, Ph.D., Asst. An. Husb. William Robertson, Ph.D., Asst.
John D. Feaste, Ph.D., An. Nutritionist Chemist
H. D. Wallace, Ph.D., Asst. An. Husb. O. E. Cruz, B.S.A., Asst. Soil Surveyor
DAIRY SCIENCE W. G. Blue, Ph.D., Asst. Biochemist
E. L. Fouts, Ph.D., Dairy Tech.'' VETERINARY SCIENCE
B.B Becker, Ph.D., Dairy Husb. D. A. Sanders, D.V.M., Veterinarian'
S. P. Marshall, Ph.D., Asso. Dairy M. W. Emmel, D.V.M., Veterinarian'
Husb.' C. F. Simpson, D.V.M., Asso.
W. A. Krienke, M.S., Asso. in Dairy Mfs.' Veterinarian
P. T. Dix Arnold, M.S.A., Asst. Dairy L. E. Swanson, D.V.M., P.iraiil:.'iglit
Husb.' Glenn Van Ness, D.V.M.. A-es Poullrv
Leon Mull, Ph.D., Asst. Dairy Tech. Pathologist
H. Wilkowske, Ph.D., Asst. Dairy Tech. G. E. Batte, D.V.M., Asso. Parasitologist










BRANCH STATIONS SUB-TROPICAL ST/
HOMESTEAD
NORTH FLORIDA STATION, QUINCY Geo. D. Ruehle, Ph.D., Vice-D,
J. D. Warner, M.S., Vice-Director in Charge
Charge D. 0. Wolfenbarger, Ph.D., Entomologist
R. R. Kincaid, Ph.D Plant Pathologist Francis B. Lincoln, Ph.D., Horticulturist
L. G. Thompson, Ph.D., Soils Chemist Milton Cobin, B.S., Asso. Horticulturist
W. C. Rhoads, M.S., Entomologist Robert A. Conover, Ph.D., Plant Path.
W. H. Chapman, M.S., Asso. Agronomist John L. Malcolm, Ph.D., Asso. Soils
Frank S. Baker, Jr., B.S., Asst. An. Chemist
Husb. R. W. Harkness, Ph.D., Asst. Chemist
Mobile Unit, Monticello W. CENT. FLA. STATION,
R. W. Wallace, B.S., Associate BROOKSVILLE
Agronomist BROOKSVILLE
William Jackson. B.S.A., Animal
Mobile Unit, Marianna Husbandman in Charge2
R. W. Lipscomb, M.S., Associate RANGE CATTLE STATION, ONA
Agronomist W. G. Kirk, Ph.D., Vice-Director in
Mobile Unit, Pensacola Charge
R. L. Smt .S ssoceAgronomist E. M. Hodges, Ph.D., Agronomist
L. Smith, M.S., Associate Aronomist D. W. Jones, M.S., Asst. Soil
Mobile Unit, Chipley Technologist
J. B. White, B.S.A., Associate CENTRAL FLORIDA STATION,
Agronomist SANFORD
CITRUS STATION, LAKE ALFRED R. W. Ruprecht, Ph.D., Vice-Dir. in
A. F. Camp, Ph.D., Vice-Director in Charge
Charge J. W. Wilson, Sc.D., Entomologist
W. L. Thompson, B.S., Entomologist P. J. Westgate, Ph.D., Asso. Hort.
J. T. Griffiths, Ph.D., Asso. Ben. F. Whitner, Jr., B.S.A., Asst. Hort.
Entomologist Geo. Swank, Jr., Ph.D., Asst. Plant Path.
R. F. Suit, Ph.D., Plant Pathologist
E. P. Ducharme, Ph.D., Asso. Plant W. FLA. STATION, JAY
Path.* C. E. Hutton, Ph.D., Vice-Director in
R. K. Voorhees, Ph.D., Asso. Charge
Horticulturist H, W. Lundy, B.S.A., Associate
C. A. Stearns, Jr., B.S.A., Asso. Chemist Agronomist
J. W. Sites, M.S.A., Horticulturist
H. 0. Sterling, B.S., Asst. Horticulturist SUWANEE VALLEY STA., LIVE OAK
H. J. Reitz, Ph.D., Asso. Horticulturist G. Ritchey, M.S., Agronomist in
Francine Fisher, M.S., Asst. Plant Path. Charge
I. W. Wander, Ph.D., Soils Chemist
J. W. Kesterson, M.S., Asso. Chemist GULF COAST STA., BRADENTON
R N. Hendrickson, B.S., Asst. Chemist
J C. Showers, M.S., Asst. Chemist E. L. Spencer, Ph.D., Soils Chemist in
D. S. PrBowssers, M B.S., Asst. Chemist Chage
"HoSrtssriurst B. E. G. Kelsheimer, Ph.D., Entomologist
R. W. Olsen, B.S., Biochemist David G. Kelbert, Asso. Horticulturist
F. W. Wenzel, Jr., Ph.D., Supervisory Robert 0.. Magie, Ph.D., Gladioli Hort.
Chem. J. M. Walter, Ph.D., Plant Pathologist
Alvin H. Rouse, M.S., Asso. Chemist Donald S. Burgis, M.S.A., Asst. Hort.
H. W. Ford, Ph.D., Asst. Horticulturist C.M. Geraldson, Ph.D., Asst. Hort.
L. W. Faville, Ph.D., Asst. Chemist
L. C. Knorr, Ph.D., Asso. Histologist'
R. M. Pratt, B.S., Asso. Ent.-Pathologist
W. A. Simanton, Ph.D., Entomologist FIELD LABORATORIES
E. J. Desyck, Ph.D., Asso. Horticulturist
C. D. Leonard, Ph.D., Asso. Horticul- Watermelon, Grape, Pasture-Leesburg
tourist G. K. Parris, Ph.D., Plant Path. in
EVERGLADES STATION, Charge
BELLE GLADE C. C. Helms, Jr., B.S., Asst. Agronomist
"R. V. Allison, Ph.D., Vice-Director in Strawberry-Plant City
Charge
Thomas Bregger, Ph.D., Sugar A. N. Brooks, Ph.D., Plant Pathologist
Physiologist *
J. W. Randolph, M.S., Agricultural Egr. Vegetables-Hastings
W. T. Forsee, Jr., Ph.D., Chemist A. H. Eddins, Ph.D., Plant Path. in
R. W. Kidder, M.S., Asso. Animal Husb. A.H. Eddins, Ph.D., Plant Path. in
C. C. Erwna Asstnt Coohemist E. N. McCubbin, Ph.D., Horticulturist
N. C. Hayslip, B.S.A., Asso. Entomolo-
gist Pecans-Monticello
E. A. Wolf, M.S., Asst. Horticulturist A. M. Phillips, B.S., Asso. Entomologist
W. H. Thames, M.S., Asst. Entomologist John R. Large, M.S., Asso. Plant Path.
W. N. Stoner, Ph.D., Asst. Plant Path.
W. A. Hills, M.S., Asso. Horticulturist Frost Forecasting-Lakeland
W. G. Genung, B.S.A., Asst. Entomologist Frost Foreeasting-Lakeland
D. W. Smith, B.S., Asst. Chemist Warren O. Johnson, B.S., Meterologist'
Frank V. Stevenson, M.S., Asso. Plant
Pathologist Head of Department
Raymond H. Webster, Ph.D., Asst. 2 In cooperation with U. S.
Agronomist s Cooperative, other divisions, U. of F.
Robert J. Allen, M.S., Asst. Agronomist On leave.


\ *^^S';




















CONTENTS



Page


Introduction ----------- --...--.....-..........---------------- 5


Experimental -.-.......- .------------..... .. ...-._ .. -._---------------------- 6


Alachua County Plots ..------..-------.---------.----...------- 7


Hardee County Plots ----.... -----..---.- -------------- 15


Santa Rosa County Plots --.....---. ..---.---- -.-.------------.. ------.-. 24


Summary and Conclusions -------.....---. ------------------- 30


Acknowledgments ---.--....... -------....-- ----------- --.... .. ---... 31


Literature Cited .-----------.....-- -------.. ----------------- 31










Sulfur Requirement of Soils for Clover-
Grass Pastures in Relation to

Fertilizer Phosphates

By
J. R. NELLER, G. B. KILLINGER, D. W. JONES, R. W. BLEDSOE
AND H. W. LUNDY


Introduction
Several types of fertilizer phosphates are of value in soil
treatments for the establishment and maintenance of improved
pastures in Florida and other Southeastern states. Superphos-
phate generally is used and finely ground rock phosphate, col-
loidal or waste pond phosphate, and agricultural basic slag also
have been applied.
Superphosphate of 18 to 20 percent P205 content contains
gypsum, also known as landplaster or calcium sulfate, whereas
the more concentrated triple superphosphate does not; neither is
there any gypsum associated with calcined phosphate, rock phos-
phate and waste pond phosphate. Small amounts of sulfate
may be found in basic slag. Gypsum supplies the soil with cal-
cium and with sulfur in soluble, sulfate form.
Arable soils often are lacking in sufficient sulfur for many
crops, especially the legumes such as clovers. Legumes require
more sulfur than most non-legumes because they contain more
protein. Their ability to grow well is dependent upon the pres-
ence of adequate amounts of sulfates in the soil to furnish the
sulfur necessary for protein formation.
Sulfur deficiency is widespread and has been found to exist
in arid and semi-arid soils (7, 8)1 where there is little or no
leaching, as well as in leached soils of the humid, regions. For
Florida, Bledsoe and Blaser (3) report a sulfur response by Red
clover and Black Medic clover grown in Leon fine sand. Sulfur
deficiency has been reported for various regions in the United
States where climatic conditions are intermediate between arid

1Italic figures in parentheses refer to "Literature Cited" in the back
of this bulletin.








6 Florida Agricultural Experiment Station

and humid and where sulfates are leached from the soil to small
or moderate extent.
Were it not for the fact that large quantities of superphos-
phate containing gypsum are used on the cropped soils of the
Southeastern states, lack of sulfur would prohibit the growth of
legumes and seriously retard non-legume crops in many localities.
For instance, a sulfur response by cotton has been found by
Younge (12) in Arkansas; by Harris, Bledsoe and Calhoun (4)
in Florida; and by Volk, Tidmore and Meadows (11) in Alabama.
Appreciable amounts of sulfur may be supplied to the soil by
rainfall in regions of industrial activity. Much less is brought
down by rain in rural areas. Using a technique to avoid accumula-
tive absorption of sulfur dioxide by the collecting vessels, Alway
(1) found that the amount of sulfur actually added to the soil by
rainfall in rural areas of Minnesota averages about 4.5 pounds
per acre per year, an amount too low to be of much consequence
for crops. It is probable that the amount of sulfur actually
brought to plant roots by rainfall is equally low in most rural
areas at a distance from industrial activity, as was found by Volk,
Tidmore and Meadows for Alabama (11). Hence cropped soils
that are deficient in native sulfur will require additions of that
element from manures or fertilizers.
In addition to the certainty that many soil types in Florida
require phosphates for clover pastures, there is a stong possibility
that a source of sulfur must be supplied also. The purpose of
this investigation was to determine how different phosphate car-
riers relate to these requirements in the central, northern, and
western parts of the state.

Experimental

The experiments were based upon field plots in Alachua,
Hardee and Santa Rosa counties. Virgin soils were selected
because there are large areas of virgin soil in these regions in
which improved pastures have been developed or are awaiting
development.
Details of the experiments vary somewhat and will be de-
scribed for each location. In addition to data on sulfur, tabula-
tions are included relative to the phosphorus status of the soils
as affected by the phosphate sources that were used. These,
together with the pH data, are basic for an interpretation of the
response of clover to sulfur.








Sulfur Requirement of Soils for Clover Grass Pastures 7

The data were analyzed statistically and the terms "signifi-
cant" and "highly significant" refer to the 5 and 1 percent levels,
respectively.2
Alachua County Plots.-Inasmuch as a clover-grass cover,
which furnishes one of the most desirable types of pasture, has
been found to do best in fairly moist soils (2), the experimental
plots were located on an area of Rutlege fine sand. This type of
soil generally occupies areas between those of the widespread
drier Leon series and the cypress ponds of the flat pine land
regions of central and northern Florida. Rutlege fine sand
differs from Leon fine sand in that it has no hardpan layer and
contains more organic matter in the surface layer. Native
vegetation is similar to that of Leon soils consisting of scattering
pines, palmetto, gallberry and wire-grass. Growth of the latter
is heavier on Rutlege fine sand (Fig. 1).
The plot area was prepared by shallow disking sufficient to
kill off wire-grass and palmetto. This was done about a year
previous to the establishment of the plots to permit partial de-
composition of the plant residues. Plots 12 by 15 feet in size
were laid off in a design of eight fertilizer treatments replicated
six times and randomized in blocks, each block consisting of two
rows of plots.
The eight variations of phosphates and gypsum are recorded
in the tables as follows: (1) superphosphate every other year,
(2) superphosphate every year, (3) rock phosphate once only,
(4) rock phosphate every two years, (5) rock phosphate every
two years and gypsum every year, (6) calcined phosphate every
two years, (7) calcined phosphate every year, and (8) calcined
phosphate with gypsum every year.
Muriate of potash (50 percent K20) was applied each year
on all of the plots at the rate of 200 pounds per acre. The super-
phosphate and calcined phosphate were used at a rate approxi-
mating that in 0-14-10 mixtures at 500 pounds per acre. The
finely ground rock phosphate was added at a rate, based on total
P205, eight times that of the citrate-soluble P205 of the super-
phosphate and of calcined phosphate. Approximate rates per acre
are 350 pounds superphosphate and of calcined phosphate and
1,800 pounds of rock phosphate. Since the superphosphate con-

2pH values were analyzed statistically without conversion to hydro-
gen ion concentrations, since the pH range of the soils under study bears
approximately a linear relationship to percent base saturation.








8 Florida Agricultural Experiment Station

trained gypsum equal to about half its weight, gypsum at 175
pounds per acre was added to the rock phosphate and calcined
phosphate plots, as called for in the treatment schedule. Inasmuch
as minor elements are known to stimulate the growth of clover in
some areas (5), the following were added to all plots when first
fertilized: sulfates of copper, manganese and zinc at 25, 10 and 5
pounds per acre, respectively; borax at 5 pounds; and magnesium
carbonate at 50 pounds per acre, the latter to supply any possible
lack of magnesium. The copper, manganese and zinc applica-
tions contained sulfates equivalent to the amount in 26 pounds
per acre of gypsum. This may have had some effect on the early
growth of clover on the plots designated not to receive sulfur.
However, since sulfates are the best type of minor element com-
pounds to use and since the sulfate ion leaches, it was considered
that the sulfur effect of these would be negligible after the first
rainy season.

Finely ground calcic limestone at two tons per acre was
machine-broadcast over the plot area November 6, 1946, and was
disked into the surface two to three inches. The fertilizer
mixtures were broadcast by hand on November 21 on each of the
plots, after which the soil was disked lightly two to three inches
deep. Inoculated white clover (Trifolium repens L.) seed and
carpet (Axonopus compressus) (Swartz) Beauv. and Pensacola
Bahia (Paspalum notatum Flugge) grass seed were broadcast
November 25. A fairly thick stand of clover seedlings became
established but the grasses were not much in evidence until the
following summer.

The clover seedlings grew slowly and by the last of January
they were about four inches high on the superphosphate plots and
on those that received gypsum. Seedlings on the corresponding
rock phosphate and calcined phosphate plots that did not receive
gypsum were smaller and lighter in color. The first cutting was
removed April 30 and, as recorded in Table 1, there was a marked
increase in growth on the plots for which the treatments included
gypsum. Clover predominated in the next three cuttings, while
those of September and October were mostly Pensacola Bahia
grass. Total growth for the year was significantly larger for
the superphosphate treatments and for that of calcined phosphate
plus gypsum than for the other treatments. During 1947 treat-
ments of superphosphate, rock phosphate and calcined phosphate
were duplicated in each of the six blocks because time of appli-









Sulfur Requirement of Soils for Clover Grass Pastures 9

TABLE 1.-POUNDS PER ACRE DRY WEIGHT OF CLOVER AND GRASS CUTTINGS
FROM PLOTS OF DIFFERENT TREATMENTS ON RUTLEGE FINE SAND, 1947.
(AVERAGES OF 6 REPLICATED PLOTS.)
Weights Cut at Different Dates
Phosphate and Gypsum Clover and Totals
Treatments White Clover Pensacola Bahia Grass for
April 30 June 5 July 2 Aug. 5 Sept. 5 Oct. 1
1. Superphosphate
every 2 years 439 544 380 525 290 127 2,305
2. Superphosphate
each year 402 538 348 485 309 113 2,195
Superphosphate
average for 1st year
of treatment 421 541 364 505 300 120 2,250
3. Rock phosphate
once only 195 349 241 372 316 183 1,656
4. Rock phosphate
every 2 years 181 198 203 296 357 111 1,346
Average for rock
phosphate, 1st year
of treatment 188 279 222 334 337 147 '1,501
5. Rock phosphate
every 2 years
plus gypsum each
year 214 244 214 490 354 156 1,672
6. Calcined phos-
phate every 2
years 337 359 210 220 238 79 1,443
7. Calcined phos-
phate each year 386 355 192 258 261 149 1,601
Average calcined
phosphate, 1st year
of treatment 362 357 201 239 230 114 1,522
8. Calcined phos-
phate plus gypsum
each year 418 566 277 472 269 167 2,169
Difference required for significance, 5% level, between totals = 459.

cation was not varied until a year after the initial application on
November 6, 1946.
The nitrogen content of the clover of the June 5 cutting
(Table 2) was significantly higher on plots that received gypsum
than on the no-gypsum treatments. This difference was highly
significant in the clover of the cutting of August 5 as well as in
the cutting of October 1, which consisted mostly of grass. Table
2 records the significant differences between treatments for the
phosphorus, calcium and potassium contents of these samples.
Soil samples of the surface three inches were obtained from
each of the plots on April 15, 1947, by compositing 10 borings per
plot. The average organic matter content ranged from 2.88 to
3.69 percent (Table 3). Differences in organic matter were
highly significant between blocks but are not significant within











TABLE 2.-COMPOSITION OF CLOVER AND GRASS CUT IN 1947 FROM PLOTS ON RUTLEGE FINE SAND. (AVERAGES OF 6 REPLICATED
PLOTS IN PERCENT ON OVEN-DRY SAND-FREE BASIS.)

Phosphate and Gypsum Treatments
1 2 3 4 5 6 7 8
Phosphate
Dates Super- Rock Every 2 Calcined Calcined Difference Necessary
of phosphate Super- Rock Phosphate Years + Phosphate Calcined Phosphate for Significance
Cuttings Every 2 phosphate Phosphate Every 2 Gypsum Every Phosphate + Gypsum
Years Each Year Once Only Years Each Year 2 Years Each Year Each Year 5% Level 1% Level

Nitrogen
June 5 3.702 3.854 3.334 3.054 3.596 3.546 3.415 3.572 0.029 0.039
Aug. 5 3.354 3.159 2.438 1.920 2.520 2.367 2.198 3.106 0.827 Not sig.
Oct. 1 2.568 2.059 1.756 1.698 2.185 1.931 1.707 2.212 0.343 0.464
Phosphorus
June 5 0.340 0.366 0.306 0.271 0.294 0.327 0.307 0.309 0.046 0.062
Aug. 5 0.280 0.271 0.234 0.198 0.210 0.243 0.236 0.244 0.045 Not sig. M
Oct. 1 0.236 0.217 0.200 0.202 0.209 0.199 0.186 0.199 Not sig. |-
Calcium
June 5 1.549 1.404 1.256 1.164 1.281 1.520 1.434 1.531 0.025 Not sig.
Aug. 5 1.551 1.468 0.977 0.648 1.003 0.996 0.917 1.531 0.106 Not sig.
Oct. 1 0.799 0.551 0.418 0.477 0.646 0.510 0.373 0.617 0.103 0.139
Potassium -
June 5 1.766 1.906 1.818 1.758 1.741 1.784 1.682 1.915 Not sig. Not sig.
Aug. 5 1.189 0.900 0.771 1.574 0.980 0.882 0.776 0.904 0.242 0.325
Oct. 1 1.447 1.355 1.210 0.965 1.255 1.065 1.025 1.364 0.136 0.168








Sulfur Requirement of Soils for Clover Grass Pastures 11

TABLE 3.-ORGANIC MATTER CONTENT, MOISTURE EQUIVALENT AND PH OF
SAMPLES OF RUTLEDGE FINE SAND TAKEN APRIL 15, 1947, FOR PLOT AREA.
(AVERAGES OF 8 PLOTS PER BLOCK.)
Difference Necessary for
Determina- Blocks Significance at 5% Level
tions 1 2 3 4 5 6 Between Blocks Within Blocks
Organic
matter,
percent 3.69 2.88 2.86 3.62 3.67 3.42 0.49* Not significant
Moisture
equivalent,
percent 7.64 7.34 6.39 7.71 8.39 7.22 Not significant Not significant
pH 5.29 5.47 5.75 5.35 5.28 5.37 Not significant Not significant
Also significantly different at the 1% level with a least significant
difference of 0.56.

blocks. Blocks 2 and 3 were adjacent to each other and their
average percentages of organic matter were significantly lower
than those of the other blocks. For moisture equivalent and pH
values there were no significant differences either between blocks
or within blocks. The pH of the plot area was 4.84 before liming.
One year after the establishment and fertilization of the plots,
a second set of soil samples was obtained for determination of
total and dilute acid-soluble (6) phosphorus (Table 4). For the
total phosphorus there was good agreement between analyses of
duplicate sub-samples, but considerable variation between repli-
cated treatments, even when a plot sample consisted of a com-
posite from 10 borings. This must be attributed to lack of uni-
formity of distribution of the fertilizer. A variation in samples
from replicated plots was anticipated and the fertilizer was
broadcast as uniformly as possible. It may be observed that there
is considerable variation in total phosphorus between groups of
replicated plots. This comparison was possible at the time of
sampling, as reapplications of the superphosphate, rock phos-
phate and calcined phosphate were not made until after the soil
samples were taken.
Results for dilute acid-soluble phosphorus show much the
same trend in variations between replicated plots. Dilute acid-
soluble phosphorus is determined for the purpose of correlating
it with available phosphorus as related to plant growth and
mineral composition. This relationship cannot be estimated until
more data have been obtained.
The pH values of the samples obtained a year after lime ap-
plication (Table 4) were slightly higher than those taken five








12 Florida Agricultural Experiment Station

TABLE 4.-TOTAL PHOSPHORUS, DILUTE ACID-SOLUBLE PHOSPHORUS, AND PH OF
THE SURFACE THREE INCHES OF PHOSPHATED AND SULFURED PLOTS OF RUTLEGE
FINE SAND, OCTOBER 14, 1947. (AVERAGES OF 6 REPLICATIONS.)
Averages of Treatments
Phosphate and Gypsum Dilute Acid- Identical for 1947
Treatments Total P soluble P pH Dilute Acid-
Total P soluble P pH
ppm. ppm. ppm. ppm.
1. Superphosphate
every 2 years 86 3.4 5.37
2. Superphosphate
each year 71 4.1 5.48 79 3.8 5.42
3. Rock phosphate
once only 348 5.3 5.48
4. Rock phosphate
every 2 years 386 7.5 5.60 367 6.4 5.52
5. Rock phosphate
every 2 years +
gypsum each year 440 6.0 5.43 440 6.0 4.40
6. Calcined phosphate
every 2 years 71 7.2 5.67
7. Calcined phosphate
each year 83 5.1 5.55 77 6.2 5.61
8. Calcined phosphate
+ gypsum each
year 78 5.5 5.51 78 5.5 5.51
Differences necessary
for significance at
5% level 106 Not sig. Not sig.

months after the lime had been applied, indicating that the maxi-
mum neutralizing effect of the lime had not been fully attained at
the earlier sampling.
On October 31, 1947, reapplications of phosphates and of
gypsum were made as recorded under treatments, Table 1. These
materials were broadcast upon the sod cover and were made be-
fore there was much new growth following the clipping of
October 1 (Table 1).
"The next clipping was on January 6, 1948, and consisted
almost entirely of White clover on plots where the treatments in-
cluded a source of sulfur (Fig. 1). As shown by the yield records
of Table 5 aind Figures 2 and 3, there was a very marked response
to sulfur as supplied by the reapplication of superphosphate and
"of gypsum with the rock phosphate and with the calcined phos-
phate.
There was a good stand of clover on the plots that received
gypsum as well as rock phosphate (Fig. 2), whereas there were
only a few stunted clover plants where gypsum was omitted.








Sulfur Requirement of Soils for Clover Grass Pastures 13

Clover grew well on the plots treated with superphosphate and
was a failure where an equal amount of soluble phosphorus was
applied as calcined phosphate, which contains no source of sulfur.
Figure 3 shows good growth of clover on superphosphate-
treated plot and on a plot that received calcined phosphate and
gypsum. Clover was a failure for a calcined phosphate residual
treatment and was poor on a superphosphate residual. The term
residual indicates that phosphates were omitted when the plots
were refertilized the previous fall. Figures 2 and 3 are typical
examples in the replicated plots of the marked response to gyp-
sum and the contrasting failure of the clover where the phosphate
carrier was lacking in gypsum.
Clover predominated in the next three cuttings following that
of January 6 and the average weight of plant material removed
from the sulfured rock phosphate and calcined phosphate plots
was six times that from plots of similar treatments that did not
receive gypsum. The amount of growth on the sulfured plots was
about equal to that on the plots that received superphosphate.

Fig. 2.-Growth of White clover and Pensacola Bahia grass on plots of
Rutlege fine sand, January 8, 1948. Rock phosphate plus gypsum, lower
left; rock phosphate, upper left; superphosphate, lower right; and calcined
phosphate residual (from previous year), upper right.
_. :ar








14 Florida Agricultural Experiment Station

Cuttings of September 9 and 27 consisted mostly of Pensacola
Bahia grass and grass from the sulfured plots averaged one-
fourth higher in weight than that from similar treatments not
sulfured, and was greener in color.
In the clipping of March 22 (Table 6) differences in nitrogen,
phosphorus, sulfur and calcium were highly significant with re-
spect to treatments. The increases in nitrogen were due to the
gypsum added with the rock phosphate and calcined phosphate, as
well as to that contained in the superphosphate (9). Increases in
phosphorus content occurred where phosphates were reapplied,
except for rock phosphate. Gypsum caused an increase in percent
calcium and the percentages of magnesium and potassium were
similar for all plots, as might be expected, since the applications
of potash and of magnesium carbonate were uniform for all.
A tall, rather mature stand of Bahia grass was removed from
the plots September 9 (Table 5). The cutting of September 27
was at a vigorously vegetative stage of the grass. Analyses for
nitrogen, phosphorus, potassium, calcium and magnesium (Table

Fig. 3.-Growth of White clover and Pensacola Bahia grass on plots on
Rutlege fine sand, January 8, 1948. Calcined phosphate plus gypsum,
lower left; calcined phosphate residual (from previous year), upper right;
superphosphate, upper left; and superphosphate residual, lower right.









Sulfur Requirement of Soils for Clover Grass Pastures 15

TABLE 5.-POUNDS PER ACRE DRY WEIGHT OF CLOVER AND GRASS CUT IN 1948 ON
PLOTS OF RUTLEGE FINE SAND. (AVERAGES OF 6 REPLICATED PLOTS.)

Dates of Cuttings
Phosphate and Gypsum Pensacola
Treatments White Clover Bahia Grass Totals
Jan. 6 Feb. 7 Mar. 22 April 28 Sept. 9 Sept. 27
1. Superphosphate
every 2 years 198 23 104 90 1121 528 2,064
2. Superphosphate
each year 567 228 520 597 929 516 3,357
3. Rock phosphate
once only 85 16 66 140 1048 538 1,893
4. Rock phosphate
every 2 years 42 20 48 95 1074 464 1,743
5. Rock phosphate
every 2 years +
gypsum each year 320 135 408 545 1510 614 3,532
6. Calcined phosphate
every 2 years 67 33 79 113 1022 458 1,772
7. Calcined phosphate
each year 79 18 104 146 1094 516 1,957
8. Calcined phosphate
+ gypsum each
year 573 246 534 620 1309 567 3,849
Difference necessary for significance, 5% level, between totals = 706.

7) showed highly significant differences with reference to fer-
tilizer treatment. An outstanding feature of the grass was a
darker green color and a marked increase in nitrogen content as
obtained where clover had grown so well because of sulfur sup-
plied by the fertilizer. Thus sulfur not only caused an increased
weight of growth but it improved the quality of the forage due to
its higher protein content. Percentage of phosphorus was signi-
ficantly increased by reapplication of superphosphate and cal-
cined phosphate but not of rock phosphate. Calcium content was
significantly increased where the fertilizer contained gypsum.
Magnesium increases paralleled those of calcium.

Hardee County Plots.-In January 1948 White-clover" was
planted at the Range Cattle Station on a series of plots of carpet
grass on Immokalee fine sand that had been fertilized with phos-
phates beginning three years before. The carpet grass was grow-
ing nicely on these plots and after phosphates and potash were
reapplied the inoculated clover seed was broadcast over the closely
clipped and partially burned sod. The soil was then disked lightly
but not enough to retard the subsequent growth of carpet grass.











TABLE 6.-CCoPoSITION OF WHITE CLOVER HARVESTED MARCH 22, 1948, ON RUTLEGE FINE SAND PLOTS. (AVERAGES OF 6
REPLICATED PLOTS IN PERCENT ON OVEN-DRY SAND-FREE BASIS.)
Phosphate and Gypsum Treatments
Difference
1 2 3 4 5 6 7 8 Necessary for
Super- Super- Rock Rock Rock Calcined Calcined Calcined Signiance
phosphate phosphate Phosphate Phosphate Phosphate Phosphate Phosphate Phosphate Si
Elements Every 2 Each Year Once Only Every 2 Every 2 Every 2 Each Year Plus Gypsum --!
Years Years Years + Years Each Year 5% 1%
CGypsum Level Level
Each Year
Nitrogen 3.573 4.821 3.107 2.980 4.495 3.12.1 3.126 4.816 0.547 0.734
Phosphorus 0.313 0.400 0.315 0.315 0.359 0.291 0.406 0.435 0.066 0.088
Sulfur 0.148 0.235 0.143 0.158 0.234 0.141 0.148 0.227 0.026 0.037
Calcium 1.190 1.542 1.121 1.023 1.523 1.047 1.097 1.673 0.307 0.412 "
Magnesium 0.212 0.233 0.178 0.185 0.227 0.166 0.186 0.221 Not sig.
Potassium 2.689 2.066 2.113 2.177 1.922 1.692 1.994 2.023 Not sig.
-t



TABLE 7.-COMPOSITION OF PENSACOLA BAHIA GRASS CLIPPED FROM PLOTS ON RUTLEGE FINE SAND ON SEPTEMBER 27, 1948.
(AVERAGES OF 6 REPLICATED PLOTS IN PERCENT ON OVEN-DRY SAND-FREE BASIS)

Phosphate and Sulfate Treatments Diff
1 2 3 4 5 6 7 8 Necesar fnr
Super- Super- Rock Rock Rock Calcined Calcined Calcined Significance
phosphate phosphate Phosphate Phosphate Phosphate Phosphate Phosphate Phosphate ii
Elements Every 2 Each Year Once Only Every 2 Every 2 Every 2 Each Year Plus Gypsum-
Years -Years Years 4+ Years Each Year 5% 1%
Gypsum Level Level
Each Year
Nitrogen 0.996 1.203 0.831 0.854 1.026 0.802 0.866 1.114 0.152 0.200
Phosphorus 0.124 0.200 0.150 0.155 0.177 0.116 0.176 0.177 0.012 0.016
Calcium 0.213 0.390 0.237 0.255 0.306 0.217 0.272 0.323 0.078 0.108
Magnesium 0.112 0.281 0.137 0.130 0.242 0.117 0.134 0.226 0.048 0.064
Potassium 0.630 0.367 0.648 0.505 0.442 0.639 0.600 0.415 0.210 0.281









Sulfur Requirement of Soils for Clover Grass Pastures 17

Clover seedlings became established but remained in a very
stunted condition on all plots that had not received gypsum, either
in the 20 percent superphosphate or as added with the calcined
phosphate and with the rock phosphate. On those plots that did
not receive gypsum the clover died off or was so stunted that none
could be harvested (Table 8). On plots that did receive gypsum
the clover was in full bloom but was so short, due to lack of soil
moisture, that the mower did not cut off much. There was more
clover on plots that were limed in 1947 as well as in 1945. A scant
cutting of clover was obtained from the plots that received basic
slag as a source of phosphorus and of sulfur, and growth was
somewhat better where the slag had been applied in 1946 as well
as in 1945 and 1947.

Plots that received a ton of lime in 1945 as well as in 1947
had an average pH of 5.78, while for those that were not limed in
1945 the average was 5.31 (Table 9). This difference in pH
caused a marked effect on growth of clover (Table 8). Had the
pH value been determined for the surface inch instead of three
inches of soil it would undoubtedly have been found to be higher
there. In the series where phosphates were applied in 1945,
1946 and 1947, pH was significantly raised by basic slag (Table
9).
The phosphorus content of the clover was not significantly


TABLE 8.-POUNDS PER ACRE OF WHITE CLOVER CLIPPED MAY 6, 1948, FROM
PLOTS OF IMMOKALEE FINE SAND WITH FERTILIZER VARIED WITH RESPECT TO
SULFATES, PHOSPHATES AND LIME. (AVERAGES OF 4 REPLICATED PLOTS,
AIR-DRY BASIS.)

Dates of
Application Sulfate and Phosphate Treatments
Phosphate Calcined Rock
Lime and None Super- Phosphate Calcined Basic Phosphates Rock
Sulfates Phosphate + Gypsum Phosphate Slag + Gypsum Phosphate
1947 1945 No 29 86 Trace 12 74 Trace
1947 growth
1947 1945 No 54 70 Trace 28 177 Trace
1946 growth
1947
1945 1945 No 214 280 Trace 58 423 Trace
1947 1947 growth
1945 1945 No 191 107 Trace 107 217 Trace
1947 1946 growth
1947
*Gypsum was applied each year to all plots designated for gypsum.









TABLE 9.--H OF SURFACE 8 INCHES OF LIMED PHOSPHATE AND SULFATE SOURCE PLOTS, IMMOKALEE FINE SAND, MAY 12, 1948. 00
(AVERAGES OF 4 REPLICATED PLOTS.)

Dates of
Application Sources of Sulfate and Phosphate
Phosphates Calcined Rock
Lime and None Super- Phosphate Calcined Basic Rock Phosphate
Sulfates phosphate + Gypsum Phosphate Slag Phosphate + Gypsum

1945 1945 5.81 5.47 5.69 5.72 6.25 5.44 5.73
1947 1946
1947
-t
1945 1945 5.81 5.59 5.88 5.98 5.89 5.77 5.89
1947 1947

Average 5.81 5.53 5.79 5.85. 6.07 5.61 5.81

1945 1945 5.03 5.07 5.07 5.25 5.79 5.36 5.22
1946
1947
1945 1945 5.23 5.11 5.13 5.29 5.45 5.40 5.25
1947

Average 5.13 5.09 5.10 5.27 5.62 5.38 5.24

Increase for 1947
ton/acre of lime 0.68 0.44 0.69 0.58 0.45 0.23 0.57

Treatment averages 5.47 5.31 5.44 5.56 5.84 5.50 5.52


Differences for the average effect of lime and for the treatment averages are significant at the 1% level with a least
significant difference of 0.53 (1% level) and 0.35 (5% level) for treatment averages.











TABLE 10.-PHOSPHORUS AND CALCIUM CONTENT OF WHITE CLOVER CUT MAY 6, 1948, FROM LIMED, PHOSPHATED AND SULFURED
PLOTS OF IMMOKALEE FINE SAND. (AVERAGES OF 4 REPLICATED PLOTS IN PERCENT AIR-DRY WEIGHT.)
Time of
Application Sulfate and Phosphate Sources
Calcined Phosphate Rock Phosphate
Lime Phosphate Superphosphate plus Gypsum Basic Slag plus Gypsum
Phosphorus Calcium Phosphorus Calcium Phosphorus Calcium Phosphorus Calcium -

1947 1945 0.220 1.102 0.237 1.374 0.232 0.843 0.240 1.180
1947

1947 1945
1946 0.258 1.251 0.277 1.626 0.206 1.130 0.316 1.654
1947
-8
1945 1945 0.230 1.398 0.207 1.354 0.206 1.307 0.266 1.850
1947 1947

1945 1945
1947 1946 0.284 1.578 0.269 1.742 0.238 1.118 0.253 1.620
1947

Treatment averages 0.248 1.332 0.248 1.524 0.221 1.100 0.269 1.576

For calcium the least significant difference, 5% level, for treatment averages is 0.189.
Differences in phosphorus content are not quite significant.

t0








20 Florida Agricultural Experiment Station

different with respect to sources of phosphorus (Table 10). For
a given phosphate it was increased in all cases, except one for
basic slag and for rock phosphate where phosphates were applied
in 1946 as well as in 1945 and 1947. The calcium content varied
significantly in that it was low in clover from the basic slag
treatments and high when gypsum was associated with the
phosphate.
Soil samples of the surface three inches were obtained from
plots where the clover grew, as well as from those where it
failed. The total and acid-soluble phosphorus data of Table 11
indicate that phosphorus was not a limiting factor, except for
the treatment where phosphates had not been applied. Table 12
records the water-soluble sulfate as sulfur in these samples and
it may be observed that it was extremely low, except where gyp-
sum had been included in the fertilizer. The plots on which
clover failed (Table 8) are those where there was very little
sulfate sulfur in the soil (Table 12). Growth on the basic slag
plots was not quite a failure but was too poor to be of any value.
For carpet grass cut September 28, 1948, the average amounts
of growth on the plots of rock phosphate and gypsum and of
superphosphate treatments were highly significantly larger than
for all others except basic slag, for which the difference was sig-
nificant (Table 13). The next best yield was from the calcined
phosphate plus gypsum treatment, followed by that of basic slag.
Herbage yields from these were significantly higher than from
the rock-phosphate, calcined-phosphate and no-phosphate treat-
ments. These results, which are the averages for both levels of
lime, show the marked effect of the presence of a source of sulfur
upon the growth of the grass during the summer following the
winter growth of clover. In several cases the growth was more
than doubled and the increase was due to the release of nitrogen
from the clover roots and debris. During the summer period of
leaching from high rainfall the non-sulfured plots, on which no
clover grew (Table 8), were probably lacking in nitrogen for the
growth of grass. Nitrogen analyses of the grass were not ob-
tained but it may be inferred that nitrogen was higher in cut-
tings from the sulfured plots, since it was found to be so in a
similar experiment on a similar type of soil (Table 7).
The average effect of the reapplication of lime in 1947 (Table
13) was to increase growth of grass but not significantly, as
based on the 5 percent level of probability.











TABLE 11.-TOTAL AND ACID- SOLUBLE PHOSPHORUS IN SURFACE THREE INCHES ON MAY 12, 1948 ON PLOTS OF IMMOKALEE FINE SAND CO
TREATED WITH PHOSPHATES, SULFATES AND LIME. (AVERAGE PPM P OF 4 REPLICATED PLOTS.)

Time of Application Sulfate and Phosphate Sources
Calcined Rock
Phos- Super- Phosphate Calcined Phosphate Rock
Lime phates None phosphate plus Gypsum Phosphate Basic Slag plus Gypsum Phosphate
Total Sol. Total Sol. Total Sol. Total Sol. Total Sol. Total Sol. Total Sol.
P P P P P P P P P P P P P

1947 1945 55 14 79 24 99 25 90 35 167 67 480 20 538 18
1947

1947 1945 .
1946 63 16 71 23 133 36 102 35 193 72 828 25 817 25
1947-

1945 1945 68 11 95 22 97 25 111 35 195 43 762 19 619 19 0
1947 1947 0

1945 1945
1947 1946 64 14 92 24 151 41 113 34 205 83 1072 20 911 38
,1947

Treatment averages 63 14 84 23 120 32 104 35 140 66 786 21 721 25 't

Total phosphorus and acid-soluble phosphorus differ highly significantly as to treatment averages, with least significant ;
differences of 13.4 and 18.0 and of 40.0 and 53.6 for the 5 and 1 percent levels, respectively.
H














TABLE 12.-WATER-SOLUBLE SULFUR IN SURFACE 3 INCHES OF PLOTS OF IMMOKALEE FINE SAND VARIOUSLY TREATED WITH SULFATES,
PHOSPHATES AND LIME. (AVERAGES OF 4 REPLICATED POTS IN PPM OF SULFUR.)

Dates of .
Application Sulfate and Phosphate Sources
Calcined Rock
Phcsphates Phosphate Phosphate
and Super- and Calcined Basic and Rock
Lime Sulfates None phosphate Gypsum Phosphate Slag Gypsum Phosphate 3.

1947 1945 2.9 19.4 12.7 1.5 0.6 11.6 6.0
1947

1947 1945 2.5 14.3 14.9 3.9 1.0 13.9 1.4
1946
1947

1945 1945 1.2 15.1 12.2 1.0 1.0 14.5 1.0
1947 1947

1945 1945 1.1 19.6 16.8 2.1 1.2 12.8 1.9
1947 1946
1947










TABLE 13.-POUNDS PER ACRE AIR-DRY CARPET GRASS CLIPPED SEPTEMBER 28, 1948, WHICH GREW DURING THE SUMMER FOLLOWING
THE CLOVER GROWTH OF MAY 1948, RECORDED IN TABLE 8. (AVERAGES OF 4 REPLICATED PLOTS.)

Dates of
Application Sulfate and Phosphate Treatments
Phosphates Calcined Rock
and Super- Phosphate Calcined Phosphate Rock
Lime Sulfates None phosphate plus Gypsum Phosphate Basic Slag plus Gypsum Phosphate "

1947 1945 885 2161 2485 1062 1679 2146 1180
1947

1947 1945
1946 1162 2568 1550 1424 1835 3214 978
1947

1945 1945 981 3056 2590 1135 2157 3768 1763
1947 1947

1945 1945
1947 1946 1387 3370 3084 1178 2483 3231 1555
1947 P

Treatment averages 1104 2789 2427 1200 2039 3090 1369

Differences between treatment averages are highly significant, with a least significant difference of 376 (5% level) and
503 (1% level). H








24 Florida Agricultural Experiment Station

In November 1948 reapplications of phosphates were made
to those plots (Table 13) where phosphates had been reapplied
in 1946 as well as in 1947. Potash and the recorded sources of
sulfur were applied to all plots and clover seed was planted but
failed to grow because of dry weather. In the spring of 1949
the plots were given a uniform application of potash and sodium
nitrate and two cuttings of carpet grass were removed. As
recorded in Table 14, there was more growth of grass in seven
out of eight groups of plots on which clover grew in 1948 (Table
8) where gypsum was used with the basic slag; and in six out
of eight groups in similar comparisons of calcined phosphate
and of rock phosphate both with and without gypsum. This
stimulation of the growth of carpet grass the second summer
after clover disappeared from the plots was not as great as that
of the first summer (Table 13), but it was significant for the
cutting of October 20 and almost so for that of August 9. The
increased growth must be attributed to the nitrogen residues of
the clover and not to the inclusion of gypsum, as the addition of
sulfur in 1948 to the sulfur-lacking phosphates where no clover
had grown was without effect (Table 14).

Santa Rosa County Plots.-Treatments to test the response
of pasture plants to sulfur, phosphorus and other elements, were
set up at the West Florida Experiment Station in quadruplicate
plots 20 feet square. Two of the replicates were on Carnegie fine
sandy loam and two on adjacent Tifton fine sandy loam. Lime
and fertilizer were broadcast October 27, 1948. The lime was
disked into the top three inches before the fertilizer was applied
and disked in to the same approximate depth. The sources of
phosphorus, gypsum and lime treatments are recorded in Table
15. Muriate of potash was applied to all plots at 100 pounds per
acre and phosphates were used at rates of citrate-soluble PsO0
equivalent to 500 pounds per acre of 20 percent superphosphate,
except the rock phosphate which was at the rate of 2,000 pounds
per acre.
Dallis grass (Paspalum dilatatum Poir) and inoculated White
clover (Trifolium repens L.) were planted November 8, 1948.
The first cutting was removed April 1, 1949, and consisted entire-
ly of clover (Table 15). The May 16 cutting was also clover,
while those of August 11 and October 11 consisted mostly of
Dallis grass in the early seed stage. In the first and second cut-
tings there was a significant response to gypsum when calcined









TABLE 14.-POUNDS PER ACRE, AIR-DRY, OF CARPET GRASS CLIPPED IN 1949 FROM PLOTS OF IMMOKALEE FINE SAND VARIOUSLY
FERTILIZED WITH CARRIERS OF SULFUR AND PHOSPHORUS. (AVERAGES OF 4 REPLICATED PLOTS.)

Dates of Application Cutting Sulfur and Phosphate Treatments in November, 1948 2
Phosphates Dates Calcined Calcined Basic Rock Rock
and in Super- Phosphate Phosphate Slag Basic Phosphate Phosphate
Lime Sulfates 1949 phosphate + Gypsum + Sulfur + Gypsum Slag + Gypsum + Sulfur

1947 1945 Aug. 9 199 209 172 177 229 147 194
1947 Oct. 20 539 405 342 604 403 494 392

1947 1945 Aug. 9 206 157 194 182 156 207 162
1946 Oct. 20 514 389 365 525 244 709 295
1947
1948
1945 1945 Aug. 9 168 204 196 185 172 195 177
1947 1947 Oct. 20 598 509 283 603 384 637 550

1945 1945 Aug. 9 173 174 190 203 193 158 190
1947 1946 Oct. 20 384 614 458 950 714 585 426
1947
1948

Clover in May 1948 (Table 8) Present Present Absent Present Absent Present Absent ^
Number of times (total of 8) that growth
was greater where clover had grown. 6 7 6
Treatment averages for
cutting of October 20 509 479 362 671 436 606 416


Least significant difference for treatment averages, cutting of Oct. 20, are 222 (5% level) and 298 (1% level.)
Differences for the Aug. 9 cutting are not significant.
CT








26 Florida Agricultural Experiment Station

phosphate was the source of phosphorus. Growth on the rock
phosphate plots was small, particularly where the lime rate was
doubled; probably because the phosphorus was not sufficiently
available. In the second cutting, growth where rock phosphate
was used was relatively better, but without response to gypsum.
The third cutting, August 11, was Dallis grass in the seed stage
and there were no significant differences in growth with respect
to sulfate and phosphate treatments. The fourth cutting, October
11, was Dallis grass in vegetative stage and in it there was a sig-
nificant response where gypsum was supplied with the calcined
phosphate. Response to basic slag was good for all cuttings and
the total amount of growth was as large as for superphosphate
and for calcined phosphate plus gypsum.
In all of the cuttings of 1949, except that of October 11,
growth in the presence of rock phosphate plus gypsum was better,
but not significantly so, for a lime application of one ton per acre
than for none.; which, in turn, was better than for two tons. The
two blocks of the eastern part of the plot area are on Carnegie
fine sandy loam, while those adjacent on the Western side are
Tifton fine sandy loam. Growth of all cuttings was larger on the
Tifton soil, but not significantly so.
There were no significant differences in the sulfur, phosphorus
and nitrogen contents of the clover cut from the plots of the vari-
ous treatments (Table 16) on April 1, 1949.
Inasmuch as these experiments relate to the possible effect of
gypsum as associated with phosphate carriers upon growth of
clover, the phosphorus status of these soils is given in Table 17.
Dilute sulfuric acid-soluble phosphorus (10) from the surface
three inches, taken at the time of the first cutting, did not show
any significant difference between the two types of soil in the
plots; whereas the total phosphorus of the Carnegie averaged
significantly higher than the Tifttnn. With respect to phosphate
treatments, there were significant differences in some cases for
soluble phosphorus but not for total phosphorus.
The soluble sulfate content of the soils as sampled when the
clover cutting was removed was found to be fairly low in general
(Table 18). It was higher where the phosphate source included
gypsum, but not significantly so. However, where superphosphate
and basic slag had been applied, soluble sulfates were as low as or
lower than where no gypsum had been used in other treatments.
The pH (Table 18) of soil on plots of Carnegie fine sandy
loam tended to be lower, but not significantly so, than on plots of














TABLE 15.-POUNDS PER ACRE, AIR-DRY, OF WHITE CLOVER AND DALLIS GRASS CUT FROM PLOTS OF CARNEGIE AND TIFTON FINE SANDY
LOAMS WITH THE FERTILIZER VARIED WITH RESPECT TO GYPSUM, SOURCE OF PHOSPHATE AND DOLOMITIC LIME. (AVERAGES OF 4
REPLICATED PLOTS.)


Gypsum, Phosphate and Lime Treatments

Basic Rock Rock Calcined Difference Necessary
Slag Rock Phosphate, Rock Phosphate, Calcined Phosphate, Super- for Significance
Cuttings and 1 Ton Phosphate Gypsum Phosphate Gypsum Phosphate Gypsum Phosphate
Lime and 1 Ton and 1 Ton and and 2 Tons and 1 Ton and 1 Ton and 1 Ton 5%0 1%
Equivalent Lime Lime Gypsum Lime Lime Lime Lime Level Level


April 1, 1949 564 206 202 119 88 370 614 423 130 181

May 16 571 690 594 518 283 587 930 750 182 273 C)

August 11 2,296 2,100 2,273 2,055 1,780 1,895 2,393 2,232 Not sig,
-t


October 11 546 602 657 551 761 565 742 598 144 200

Total for 1949 4,377 3,598 3,726 3,243 2,912 3,417 4,679 4,003 523 725



Co

















TABLE 16.-COMrPOSITION OF WHITE CLOVER AND DALLIS GRASS OF APRIL 1, TABLE 15. PERCENT OF AIR-DRY WEIGHT, AVERAGES OF
4 REPLICATED PLOTS.



Gypsum, Phosphate and Lime Treatments
Difference
Basic Slag Rock Rock Rock Rock Calcined Calcined Super- Necessary
Elements and 1 ton Phosphate Phosphate, Phosphate Phosphate, Phosphate Phosphate, phosphate for
Lime and 1 Ton Gypsum and and Gypsum and and 1 Ton Gypsum and and Significance $
Equivalent Lime 1 Ton Lime Gypsum 2 Tons Lime Lime 1 Ton Lime Lime at 5% Level


Phosphorus 0.330 0.299 0.293 0.285 0.260 0.308 0.283 0.291 Not sig.

Sulfur 0.225 0.238 0.248 0.238 0.218 0.233 0.225 0.255 Not sig. ,

Nitrogen 3.820 3.820 3.903 3.790 3.485 3.903 3.668 3.940 Not sig. tr









Sulfur Requirement of Soils for Clover Grass Pastures 29

Tifton fine sandy loam. There were significant pH differences be-
tween treatments involving no lime, one ton and two tons of lime
per acre.

TABLE 17.-TOTAL AND SOLUBLE PHOSPHORUS IN CARNEGIE AND TIFTON FINE
SANDY LOAM FERTILIZED WITH PHOSPHATES AND GYPSUM. AVERAGES OF
DUPLICATE PLOTS IN PPM. OF PHOSPHORUS.
(1) (2)
Fertilizer Treatment Total Phosphorus Soluble Phosphorus
Carnegie Tifton Carnegie Tifton Average
No phosphate and no lime 114 101 5.2 10.5 7.9
Lime only 120 100 3.0 7.1 5.1
Rock phosphate and lime 483 440 125.0 165.0 145.0
Rock phosphate, gypsum
and lime 408 427 126.0 179.0 152.5
Rock phosphate and gypsum 370 379 129.0 191.0 160.0
Rock phosphate, gypsum
and double lime 420 417 75.0 103.0 89.0
Calcined phosphate 170 145 14.6 18.3 16.5
Calcined phosphate plus
gypsum 169 148 7.6 15.4 11.5
Superphosphate 148 138 6.6 9.3 8.0
Basic slag 164 147 11.3 17.1 14.2
(1) Average total phosphorus of soils differ significantly at the 5% level.
(2) Average soluble P of treatments differ significantly with a least
significant difference of 4.4 at the 5% level.

TABLE 18.-SOLUBLE SULFUR IN PPM. S AND PH OF SURFACE THREE INCHES OF
CARNEGIE AND TIFTON FINE SANDY LOAMS, APRIL 1, 1949, AFTER TREATMENT
WITH VARIOUS SOURCES OF PHOSPHATES AND WITH DOLOMITIC LIME.
(AVERAGES OF DUPLICATE PLOTS.)
Soluble Sulfate pH
Fertilizer Treatment Carnegie Tifton Average Carnegie Tifton Average
ppm. ppm.
No phosphate and no
lime 0.0 0.2 0.1 5.34 5.42 5.38
Lime 0.4 0.0 0.2 5.80 5.74 5.76
Rock phosphate and
lime 3.6 3.8 3.7 5.89 5.90 5.90
Rock phosphate,
gypsum and lime 4.0 5.7 4.9 5.67 5.93 5.80
Rock phosphate and
gypsum 5.5 4.3 4.9 5.29 5.31 5.30
Rock phosphate, gyp-
sum and double lime 5.6 2.8 4.2 6.00 6.06 6.03
Calcined phosphate
and lime 1.5 1.5 1.5 5.85 6.05 5.95
Calcined phosphate,
gypsum and lime 4.1 2.8 3.5 5.79 5.88 5.84
Superphosphate and
lime 2.0 1.3 1.7 5.80 5.86 5.83
Basic slag and lime
equivalent 0.4 0.4 0.4 5.81 5.96 5.89
With respect to treatments, average pH values are significantly differ-
ent, at the 5% level, with a least significant difference of 0.15; and average
soluble sulfur values differ highly significantly, with a least significant
difference of 2.4 (5% level) and of 3.2 (1% level).








30 Florida Agricultural Experiment Station

Summary and Conclusions
Field plots in replicated randomized blocks were established in
three areas in central and western Florida to determine require-
ments of White clover and associated grasses for sulfur in rela-
tion to phosphate carriers. The plots were located on soil types
suitable for pasture development. Fertilizer phosphate, such as
finely ground rock phosphate and heat-treated or calcined phos-
phate that do not contain a source of sulfur, were supplemented
with gypsum to equal the amount present in the superphosphate
treatments.
White clover on Rutlege fine sand (Alachua County) was very
stunted unless gypsum was present with the phosphate in con-
junction with adequate applications of lime and potash. Subse-
quent growth of Pensacola Bahia grass was increased highly sig-
nificantly (1 percent level) where clover grew the previous win-
ter. The nitrogen content of the grass was likewise significantly
increased (5 percent level) where clover had grown. Soil analysis
showed that soluble phosphorus was adequate on all plots but that
sulfate sulfur was lacking where the fertilizer did not contain
gypsum.
On plots located on Immokalee fine sand (Hardee County) the
same general results were obtained. Clover failed in the absence
of gypsum and subsequent growth of grass, in this case carpet
grass, was greatly benefited by previous growth of clover. These
results correlated with the sulfate content of the soil.
Clover on the plots of Tifton and Carnegie fine sandy loam
(Santa Rosa County) was better when gypsum was added with
calcined phosphate, a sulfur-free source of phosphorus, than with
calcined phosphate without gypsum. Growth on the plots treated
with basic slag was as good as on those that received superphos-
phate.
Rock phosphate, finely ground, at 2,000 pounds per acre was
an adequate source of phosphorus for the clover and grass on the
Immokalee and Rutlege fine sand flatwoods area of central and
north central Florida, but not on the Tifton and Carnegie fine
sand loams of west Florida.
Data are recorded on sulfate sulfur, total phosphorus, soluble
phosphorus, pH, organic matter and moisture equivalent of the
soils on which the plots are located. Mineral composition of
clover and grass is also recorded.
It may be concluded that in widespread areas of central and









Sulfur Requirement of Soils for Clover Grass Pastures 31

north central Florida, clover and other legumes require annual
fertilization with gypsum or some sulfur source. The experi-
ments indicate that the soils of West Florida may be a similar
category but more data are needed before a specific recommenda-
tion can be given. Ordinary superphosphate (18 to 20 percent
P20O) supplies the gypsum. Other sources of phosphorus, such as
finely ground rock phosphate, calcined phosphate, triple super-
phosphate and sometimes basic slag, must be supplemented with
a source of sulfur for satisfactory growth of clover in these areas.
It is strongly possible that many non-leguminous crops likewise
must be supplied with a source of sulfur for best growth.
In addition to the necessity for its annual application for the
growth of clover over widespread areas in Florida, gypsum has a
very important secondary effect in that the clover residues pro-
vide a source of nitrogen necessary for high protein content and
good growth of associated grasses during the summer period.
This clover nitrogen not only dispenses with the need of nitrogen
in the fertilizer, but it serves better than additions of nitrate
nitrogen in that it becomes slowly available and soluble and is not,
therefore, subject to so rapid a loss by leaching.

ACKNOWLEDGMENTS
The authors are indebted to Dr. E. M. Hodges, Agronomist, Range Cattle
Station, Ona, to Dr. Nathan Gammon, Jr., Soils Chemist, and to Dr. R. A.
Carrigan, Biochemist, Main Station, for their kind participation in phases
relating to these experiments. Mr. W. H. Kelly, Miss Carolyn Kelley and
Miss Sara Demaree assisted with the chemical analyses. Prof. W. D. Hanson
and Mr. Kelley were consulted relative to the statistical analyses.

Literature Cited
1. Alway, F. J. A nutrient slighted in agricultural research. Jour. Am.
Soc. Agron. 32: 913-921. 1940.
2. Blaser, R. E., and W. E. Stokes. Effect of fertilizer on growth and
composition of carpet and other grasses. Fla. Agr. Exp. Sta. Bul. 390.
1948.
3. Bledsoe, R. W., and R. E. Blaser. The influence of sulfur on the yield
and composition of clovers fertilized with different sources of phos-
phorus. Jour. Am. Soc. Agron. 39: 146-152. 1947.
4. Harris, H. C., R. W. Bledsoe and P. W. Calhoun. Response of cotton to
sulfur fertilization. Jour. Am. Soc. Agron. 37: 323-329. 1945.
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6. Morgan, M. F. Chemical soil diagnosis by the Universal Soil Testing
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32 Florida Agricultural Experiment Station

7. Neidig, R. E., G. R. McDole and H. P. Magnuson. Effect of sulfur,
calcium, and phosphorus on the yield and composition of alfalfa on six
types of Idaho soils. Soil Sci. 16: 127-136. 1923.
8. Neller, J. R. The influence of sulfur and gypsum upon the composition
and yield of legumes. Wash. Agr. Exp. Sta. Bul. 190. 1925.
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