• TABLE OF CONTENTS
HIDE
 Front Cover
 Front Matter
 Description of soils
 Collection and preparation...
 Methods of analysis
 Results of chemical analyses
 Comparison of some grove soils...
 General discussion
 Summary
 Literature cited
 Appendix














Group Title: Bulletin / University of Florida. Agricultural Experiment Station ;, no. 340
Title: Chemical studies on soils from Florida citrus groves
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00015119/00001
 Material Information
Title: Chemical studies on soils from Florida citrus groves
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 50 p. : charts ; 23 cm.
Language: English
Creator: Peech, Michael, 1909-
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1939
 Subjects
Subject: Soils -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 38-40.
Statement of Responsibility: by Michael Peech.
General Note: Cover title.
Funding: Bulletin (University of Florida. Agricultural Experiment Station) ;
 Record Information
Bibliographic ID: UF00015119
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000924570
oclc - 18214759
notis - AEN5197

Table of Contents
    Front Cover
        Page 1
    Front Matter
        Page 2
    Description of soils
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
    Collection and preparation of samples
        Page 8
    Methods of analysis
        Page 8
        Page 9
    Results of chemical analyses
        Page 10
        Exchange capacity and the degree of base saturation
            Page 11
            Page 12
            Page 13
            Page 14
            Page 15
        Exchangeable bases
            Page 16
            Page 17
            Page 18
            Page 19
            Page 20
            Page 21
            Page 22
            Page 23
        Organic matter
            Page 24
        Total nitrogen, nitrate nitrogen, and the c/n ratio
            Page 25
            Page 26
            Page 27
        Acid-soluble and water-soluble phosphorus
            Page 28
            Page 29
            Page 30
            Page 31
            Page 32
    Comparison of some grove soils with the adjoining virgin soils
        Page 33
    General discussion
        Page 33
        Page 34
    Summary
        Page 35
        Page 36
        Page 37
    Literature cited
        Page 38
        Page 39
        Page 40
    Appendix
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
Full Text


November, 1939


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA
WILMON NEWELL, Director







CHEMICAL STUDIES

ON SOILS FROM

FLORIDA CITRUS GROVES


By MICHAEL PEECH






TECHNICAL BULLETIN








Single copies free to Florida residents upon request to
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA


Bulletin 340










EXECUTIVE STAFF
John J. Tigert, M.A., LL.D., President of
the University3
Wilmon Newell, D.Sc., Director3
Harold Mowry, M.S.A., Asst. Dir., Research
V. V. Bowman, M.S.A., Asst. to the Director
J. Francis Cooper, M.S.A., Editor3
Jefferson Thomas, Assistant Editor3
Clyde Beale, A.B.J., Assistant Editor3
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Managers
K. H. Graham, Business Manager3
Rachel McQuarrie, Accountant3

MAIN STATION, GAINESVILLE
AGRONOMY
W. E. Stokes. M.S., Agronomist'
W. A. Leukel, Ph.D., Agronomists
G. E. Ritchey, M.S., Assoicate2
Fred H. Hull, Ph.D., Associate
W. A. Carver, Ph.D., Associate
John P. Camp, M.S., Assistant
Roy E. Blaser, M.S., Assistant
ANIMAL HUSBANDRY
A. L. Shealy, D.V.M., Animal Husbandman' '
R. B. Becker, Ph.D., Dairy Husbandmans
L. M. Thurston, Ph.D., Dairy Technologist
W. M. Neal, Ph.D., Asso. in An. Nutrition
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarian3
- R. Mehrhof, M.Agr., Poultry Husbandmans
0. W. Anderson, M.S., Asst. Poultry Husb.3 4
W. G. Kirk, Ph.D., Asso. An. Husbandman'
R. M. Crown, M.S.A., Asst. in An. Husb.3
P. T. Dix Arnold, M.S.A., Assistant Dairy
Husbandman3
L. L. Rusoff, M.S., Asst. in An. Nutrition3
CHEMISTRY AND SOILS
R. V. Allison, Ph.D., Chemist' 3
F. B. Smith, Ph.D., Microbiologists
C. E. Bell, Ph.D., Associate Chemist
Gaylord Volk, M.S., Chemist
H. W. Winsor, B.S.A., Assistant Chemist
J. Russell Henderson, M.S.A., Associates
L. H. Rogers, M.A., Asso. Biochemist
Richard A. Carrigan, B.S., Asst. Chemist

ECONOMICS, AGRICULTURAL
C. V. Noble, Ph.D., Agricultural Economist'
Bruce McKinley, A.B., B.S.A., Associate
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Assistant
ECONOMICS, HOME
Ouida Davis Abbott, Ph.D., Specialist'
Ruth Overstreet, R.N., Assistant
R. B. French, Ph.D., Associate Chemist

ENTOMOLOGY
J. R. Watson, A.M., Entomologist'
A. N. Tissot, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant
HORTICULTURE
G. H. Blackmon, M.S.A., Horticulturist'
A. L. Stahl, Ph.D., Associate
F. S. Jamison, Ph.D., Truck Horticulturist8
R. J. Wilmot, M.S.A., Specialist, Fumigation
Research
R. D. Dickey, M.S.A., Assistant Horticulturist
J. Carlton Cain, B.S.A., Asst. Horticulturist
Victor F. Nettles, M.S.A., Asst. Hort.

PLANT PATHOLOGY
W. B. Tisdale, Ph.D.; Plant Pathologist1
George F. Weber, Ph.D., Plant Pathologists
L. O. Gratz, Ph.D., Plant Pathologist
Erdman West, M.S., Mycologist
Lillian E. Arnold, M.S., Assistant Botanist


BOARD OF CONTROL
C. P. Helfenstein, Acting Chairman, Live Oak
W. M. Palmer, Ocala
H. P. Adair, Jacksonville
R. H. Gore, Fort Lauderdale
N. B. Jordan, Quincy
J. T. Diamond, Secretary, Tallahassee

BRANCH STATIONS
NORTH FLORIDA STATION, QUINCY
J. D. Warner, M.S., Agronomist Acting in
Charge
R. R. Kincaid, Ph.D., Asso. Plant Pathologist
Jesse Reeves, Farm Superintendent
Elliott Whitehurst, B.S.A., Asst. An. Husb.

CITRUS STATION, LAKE ALFRED
A. F. Camp, Ph.D., Horticulturist in Charge
John H. Jefferies, Superintendent
Michael Peech, Ph.D., Soils Chemist
B. R. Fudge, Ph.D., Associate Chemist
W. L. Thompson, B.S., Asso. Entomologist
W. W. Lawless, B.S., Asst. Horticulturist
R. K. Voorhees, M.S., Asst. Plant Path.

EVERGLADES STATION, BELLE GLADE
J. R. Neller, Ph.D., Biochemist in Charge
J. W. Wilson, Sc.D., Entomologist
F. D. Stevens, B.S., Sugarcane Agronomist
Thomas Bregger, Ph.D., Sugarcane
Physiologist
Frederick Boyd, Ph.D., Asst. Agronomist
G. R. Townsend, Ph.D., Plant Pathologist
R. W. Kidder, M.S., Asst. An. Husbandman
W. T. Forsee, Ph.D., Asso. Chemist
B. S. Clayton, B.S.C.E., Drainage Engineer2

SUB-TROPICAL STATION, HOMESTEAD
W. M. Fifield, M.S., IHorticulturist Acting in
Charge
S. J. Lynch, B.S.A., Asst. Horticulturist
Geo. D. Ruehle, Ph.D., Asso. Plant Pathologist

W. CENTRAL FLA. STA., BROOKSVILLE
W. F. Ward, M.S., Asst. An. Husbandman
in Charge2

FIELD STATIONS
Leesburg
M. N. Walker, Ph.D., Plant Pathologist in
Charge
K. W. Loucks, M.S., Asst. Plant Pathologist
Plant City
A. N. Brooks, Ph.D., Plant Pathologist
R. N. Lobdell, M.S., Asst. Entomologist
Cocoa
A. S. Rhoads, Ph.D., Plant Pathologist
Hastings
A. H. Eddins, Ph.D., Plant Pathologist
Monticello
Samuel O. Hill, B.S., Asst. Entomologist
Bradenton
Jos. R. Beckenbach, Ph.D., Truck Horticul-
turist in Charge
David G. Kelbert, Asst. Plant Pathologist
Sanford
R. W. Ruprecht, Ph.D., Chemist in Charge,
Celery Investigations
W. B. Shippy, Ph.D., Asso. Plant Pathologist
Lakeland
E. S. Ellison, Meteorologist2
B. H. Moore, A.B., Asst. Meteorologist2

1Head of Department.
2In cooperation with U.S.D.A.
Cooperative, other divisions, U. of F.
4On leave.








CHEMICAL STUDIES ON SOILS FROM FLORIDA

CITRUS GROVES

By MICHAEL PEECH
CONTENTS Page
DESCRIPTION OF SOILS ........................................ ........... .......................... ...... 3
COLLECTION AND PREPARATION OF SAMPLES ......... ....................................... 8
M ETHODS OF ANALYSIS ...........................-...... ..................... ............... ....... 8
RESULTS OF CHEMICAL ANALYSES ........................................... ................ 10
Exchange Capacity and the Degree of Base Saturation ................... 11
Exchangeable Bases ...........- ....-. ................. ..- ....... ..... 16
Calcium ............................. ............................ .... .............. 16
M agnesium .......................................... ..... ....... ..... ........... 16
Potassium ........................................... ................. .......... .. 17
M anganese .................... ........... -........ .... ..... ... ...... ..... .... ...-..... 18
C opper ............ ..... ..... .... ................................. .................. ........................ .. 20
Z in c .......................................... ........ ............................ ............. 22
O organic M matter ........................................... ............... ................ .. 24
Total Nitrogen, Nitrate Nitrogen, and the C/N Ratio ........................ 25
Acid-Soluble and Water-Soluble Phosphorus ..................................... 28
COMPARISON OF SOME GROVE SOILS WITH THE ADJOINING VIRGIN SOILS ........ 33
GENERAL D ISCUSSION ............................................. ................................ 33
S U M M ARY 5............................. .......... ..... .. .... ........... ............ .................... 35
LITERATURE CITED ........... ......... ... ..... .. ... .. ........... ........................... .... 38

Although it is generally conceded among citrus growers of
Florida that certain soils are more fertile than others, very
little systematic information is available regarding the varia-
tion in chemical composition of the different groups of soils
planted to citrus or the extent of the variation within a given
group or series. A knowledge of the chemical composition of
grove soils not only is of importance to proper fertilization and
soil management but such information should prove invaluable
to a better understanding of some of the important grove prob-
lems associated with the various soils.
The main purpose of this publication is to present chemical
data on representative soil types and in a general way to evaluate
the fertility of the various groups of soils planted to citrus on
the basis of their chemical composition. The soils included in
this study were collected in a survey made in 1937 (4l)1 of
approximately 100 groves located in the various citrus areas
of the state and covering a wide range of grove conditions on
different soil types. Detailed notes were made by Walter
Reuther of the Citrus Experiment Station staff in regard to
the past fertilizer practices and the condition of the groves at
the time the samples were taken.

DESCRIPTION OF SOILS
The soils planted to citrus in Florida may be divided into two
major groups, (1) well drained soils, and (2) poorly drained
soils. According to the classification established by the Bureau

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







4 Florida Agricultural Experiment Station

of Chemistry and Soils of the U. S. Department of Agriculture,
soils are grouped into series on the basis of origin, color, struc-
ture, and other characteristics. The series are further sub-
divided into types according to their texture or the relative
amount of sand, silt, and clay in the surface layer. Thus, Nor-
folk sand and Norfolk fine sand are different types belonging
to the Norfolk series.
WELL DRAINED SOILS
The principal soils planted to citrus within the well drained
group include the following series: Norfolk, Blanton, Eustis,
Lakewood, Orlando, and Gainesville. The well drained and roll-
ing uplands are commonly referred to as "high pineland" in the
ridge section and other parts of central Florida and are by far
the predominant soils utilized for citrus in the state, having
been planted extensively during the heaviest development of
citrus, and constitute at least 70 percent of the total present
acreage. Because of their excellent cold protection due to proper
air drainage they are highly prized soils for this purpose, al-
though their natural fertility is very low. In the natural state
these soils support a forest growth consisting of long-leaf pine
(Pinus australis Michx. f.), live oak (Quercus virginiana Mill.),
turkey oak (Q. cinerea Michx.), and blackjack oak (Q. laevis
Walt.), the type of growth being more or less indicative of
the natural fertility of the soil.\ The better grades of soils in
this group ("high pineland") show a preponderance of long-
leaf pine (Pinus australis Michx. f.), turkey oak (Q. cinerea
Michx.), and a few scattered live oaks (Q. virginiana Mill.),
while the principal growth on poorer soils (commonly called
"blackjack-oak land") consists of blackjack oak (Q. laevis
Walt.) and scrub oaks (Q. Chapmanii, Q. Rolfsii, Q. myrtifolia,
Q. geminata). Some of the best soils within the group (Norfolk
fine sand, hammock phase; Eustis fine sand, dark-colored phase;
Orlando fine sand; and Gainesville find sand) locally known as
"high-hammock land" support predominantly a heavy hardwood-
hammock growth, which consists principally of long-leaf pine
(Pinus australis Michx. f.), live oak (Q. virginiana Mill.),
hickory (Hicoria spp.), magnolia (Magnolia grandiflora L.),
myrtle (Myrica spp.), and dogwood (Cynoxylon floridum (L.)
Raf.). The surface layer is usually thicker and darker due to
the higher organic matter content, and consequently the fertility
of these soils is naturally higher than that of the high pinelands.







Chemical Studies on Soils from Florida Citrus Groves 5

POORLY DRAINED SOILS
The important soils in this group planted to citrus occur
along the East and West coasts and in other areas over the
Florida peninsula; and are commonly referred to as "low
hammocks", "palmetto flatwoods", "grassy flatwoods", and
"prairies", depending upon the vegetative growth, drainage
conditions, and topography of the land. The "low hammocks"
are characterized by a heavy growth of live oak (Quercus vir-
giniana Mill.), water oak (Q. nigra L.), slash pine (Pinus
palustris Mill., and P. caribaea Morelet in South Florida), cedar
(Sabina silicicola Small.), hickory (Hicoria spp.), magnolia
(Magnolia grandiflora L.), cabbage palmetto (Sabal Palmetto
(Walt.) Todd.) with a heavy undergrowth of saw-palmetto
(Serenoa repens (Bartr.). Small), myrtle (Myrica spp.) and
other shrubs, the type of growth being dependent to some extent
on the soil type and the latitude. The hammock growth on cal-
careous soils (Parkwood series), locally known as "marl ham-
mocks" is confined almost entirely to cabbage palmetto (Sabal
Palmetto (Walt.) Todd.) and live oak (Q. virginiana Mill.),
while a mixed growth of pine and hardwood predominates on
the more acid soils.
The principal flatwoods soils that are utilized for citrus in-
clude the Scranton, Bladen, Coxville, and Portsmouth series.
In addition, small areas of Leon and St. Johns soils are also
planted to citrus, although the presence of a well developed
organic hardpan at a depth between 10 and 36 inches below
the surface renders these soils unsuitable for this purpose.
Because of their high organic matter content, several of the
soils in this group when properly drained constitute some of
the best land in the state.
Following is a brief description of important soils included
in the present study. For a more complete description of these
soils as well as of other soils not discussed in this publication,
the reader is referred to the individual county soil survey reports
and maps published by the Bureau of Chemistry and Soils, and
the State Geological Survey, and to the Florida Agricultural
Experiment Station Bulletin No. 334.2
Norfolk soils represent the well drained, undulating to rolling
"high pineland" and "blackjack oak land". They are character-
ized by about 4 to 6 inches of yellowish-gray or dark-gray sand

'The Soils of Florida, by J. R. Henderson.







Florida Agricultural Experiment Station


underlain by a yellow sand which passes into compact sandy
clay beds at varying depths below the surface. These soils grade
from a coarse sand (Norfolk sand) containing very little organic
matter, commonly called "blackjack oak land" to a much finer
sand (Norfolk fine sand), the surface layer of which is gray to
dark-gray, usually having a higher content of organic matter
and frequently referred to as "high pineland". Some of the
better Norfolk soils (Norfolk fine sand, hammock phase) have
a hammock or predominantly hardwood growth. The Norfolk
soils are the most extensive soils planted to citrus in the state.
Blanton soils occupy lower areas or depressions when in asso-
ciation with the Norfolk soils or slight knolls within and sur-
rounding the flatwoods. These soils differ from the Norfolk
soils in that the subsoil is a pale yellow fine sand splotched
with gray to grayish-yellow and underlain at varying depths,
3 to 6 feet or lower, by sandy clay beds.
Eustis soils. The surface layer of Eustis soils consists of
5 to 7 inches of a dark to grayish-brown fine sand which is under-
lain by a light reddish-yellow to yellowish-red fine sand. The
subsoil rests on sandy clay beds several feet below the surface.
Lakewood soils have a surface layer of light gray fine sand
4 to 6 inches in thickness grading abruptly into a white inco-
herent fine sand 8 to 20 inches thick. This is underlain by a
yellow to orange loose fine sand which at varying depths rests
on reddish mottled sandy clay. Although the fertility of these
soils is usually very low, they make satisfactory citrus land
where the gray surface layer is at least 6 inches deep and
contains an appreciable amount of organic matter and the layer
of white incoherent sand is only 4 to 8 inches in thickness.
Orlando soils belong to the better group of well drained soils
called "high-hammock lands". The surface layer, consisting of
very dark-gray fine sand ranging from 8 to 12 inches or more
in thickness and high in organic matter, is underlain by a gray
loose fine sand which grades into yellow or grayish yellow fine
sand at lower depths. This extends to a depth of about 5 feet
overlying clay beds.
Gainesville soils, although not planted extensively to citrus,
represent some of the most fertile "high-hammock land" in the
citrus belt. The surface layer consists of brownish-gray loamy
fine sand underlain by a reddish-brown sandy subsoil which is
often quite loamy due to the presence of clay. These soils are







Chemical Studies on Soils from Florida Citrus Groves 7

derived from residual material resulting from the disintegration
of limestone mixed with deposits of sand and are underlain by
limestone or coquina rock.
Parkwood soils are "low-hammock lands" supporting a heavy
growth of cabbage palmetto (Sabal Palmetto (Walt.) Todd.),
live oak (Quercus virginiana Mill.), magnolia (Magnolia grandi-
flora L.) and other hardwoods. The typical soil profile consists
of a dark-gray to almost black loamy fine sand which at 2 or 3
feet passes into a whitish marly clay. Since these soils are quite
variable, two different Parkwood soil profiles will be described.3
Good groves are 'invariably found on Parkwood soils having a
profile similar to the one found in grove No. 85, samples No.
142-4, as given in Appendix Table 1. The-surface layer (sam-
ple No. 142) consisted of 8 inches of dark-gray loamy fine sand,
underlain by.10 inches of dingy-brown loamy fine sand (sample
No. 143) which changed abruptly into a very plastic, slightly
mottled yellowish clay (sample No. 144) about 6 inches in thick-
ness resting upon marl and calcareous rock. The soil profile
as found in grove No. 91, samples No. 145-6, is typical of the
socalled "marl spots" which were found frequently associated
with poor groves, due to a certain grove condition to be described
later. The soil profile in this case consisted of i6 inches of very
dark-gray toalmost black sandy loam (sample No. 145) under-
lainlifmmediately by a grayish to creamy-white layer of marl
(sample No. 146).
Portsmouth soils are perhaps the most extensively used poorly-
drained soils in the state. Many groves on acid soils in "low-
hammock" areas along the East and West Coasts are located
on Portsmouth soils. The surface layer is a dark-gray to gray
fine sand 6 to 8 inches deep and very acid in reaction, underlain
by a light-gray to almost white sandy subsoil which at varying
depths several feet below the surface passes into a sticky gray,
yellowish and blue-mottled sandy clay. When these soils are
properly drained their fertility, like that of well drained soils,
is very much dependent on the amount of organic matter in the
surface layer.
Bladen soils make excellent land for citrus when properly
drained. However, only a very small percentage of Bladen soils
is planted to citrus. The soil profile as found in grove No. 93
consisted of 10 inches of gray to dark-gray loamy fine sand
"It is probable that several new series may be established to characterize
these calcareous soils after the soil surveys are completed.






Florida Agricultural Experiment Station


(sample No. 268) underlain by yellowish-gray plastic sandy
clay (sample No. 269) which usually becomes heavier and more
plastic with increasing depth and rests on bluish-gray clay
mottled in places with yellow and brown.

COLLECTION AND PREPARATION OF SAMPLES
In the past fertilizer has been applied commonly over a cir-
cular area slightly larger than the actual spread of the tree;
however, many growers are now spreading the fertilizer in older
groves over the entire area by means of fertilizer-distributing
machines. As a result, the soil is usually more acid in the area
within the tree spread than in the middle of the checks. After
a preliminary study, it was decided to take the soil samples
just beyond the periphery of the tree or immediately outside
the area of maximum leaf drip. At least 12 borings were made
for each sample by means of a stainless steel tube 11/2 inches
in diameter, one boring to a tree, separating all well defined soil
horizons. In most of the light sandy soils in which the profile
is quite simple, samples were obtained at two different depths,
the gray or dark surface layer 5 to 7 inches thick being separated
from the yellow, reddish-yellow, grayish-white or light-gray
subsoil. The subsoil sample was taken to an arbitrary depth
of 18 inches except where there was a definite change in the
soil profile horizon within this depth. Both the surface soil and
the subsoil borings were composite separately in the field and
brought to the laboratory in quart glass jars where they were
air-dried, screened through a 2 mm. aluminum sieve, and thor-
oughly mixed.
METHODS OF ANALYSIS
The exchangeable bases (calcium, magnesium, potassium, and
manganese) were extracted by leaching a 200-gram sample of
soil in a Buchner funnel with 800 ml. of 1 N ammonium acetate
adjusted to pH 7.0. After washing out the excess ammonium
acetate with 500 ml. of 80 percent neutral alcohol, the absorbed
ammonium was replaced by leaching with 500 ml. of 10 percent
solution of sodium chloride and determined by distillation in the
presence of calcium hydroxide. The ammonium acetate extract
containing the exchangeable bases was evaporated to dryness,
and the organic matter destroyed by means of hydrogen perox-
ide. After dehydrating the silica, the residue was dissolved in
dilute HC1, filtered, and made up to a volume of 100 ml.






Florida Agricultural Experiment Station


(sample No. 268) underlain by yellowish-gray plastic sandy
clay (sample No. 269) which usually becomes heavier and more
plastic with increasing depth and rests on bluish-gray clay
mottled in places with yellow and brown.

COLLECTION AND PREPARATION OF SAMPLES
In the past fertilizer has been applied commonly over a cir-
cular area slightly larger than the actual spread of the tree;
however, many growers are now spreading the fertilizer in older
groves over the entire area by means of fertilizer-distributing
machines. As a result, the soil is usually more acid in the area
within the tree spread than in the middle of the checks. After
a preliminary study, it was decided to take the soil samples
just beyond the periphery of the tree or immediately outside
the area of maximum leaf drip. At least 12 borings were made
for each sample by means of a stainless steel tube 11/2 inches
in diameter, one boring to a tree, separating all well defined soil
horizons. In most of the light sandy soils in which the profile
is quite simple, samples were obtained at two different depths,
the gray or dark surface layer 5 to 7 inches thick being separated
from the yellow, reddish-yellow, grayish-white or light-gray
subsoil. The subsoil sample was taken to an arbitrary depth
of 18 inches except where there was a definite change in the
soil profile horizon within this depth. Both the surface soil and
the subsoil borings were composite separately in the field and
brought to the laboratory in quart glass jars where they were
air-dried, screened through a 2 mm. aluminum sieve, and thor-
oughly mixed.
METHODS OF ANALYSIS
The exchangeable bases (calcium, magnesium, potassium, and
manganese) were extracted by leaching a 200-gram sample of
soil in a Buchner funnel with 800 ml. of 1 N ammonium acetate
adjusted to pH 7.0. After washing out the excess ammonium
acetate with 500 ml. of 80 percent neutral alcohol, the absorbed
ammonium was replaced by leaching with 500 ml. of 10 percent
solution of sodium chloride and determined by distillation in the
presence of calcium hydroxide. The ammonium acetate extract
containing the exchangeable bases was evaporated to dryness,
and the organic matter destroyed by means of hydrogen perox-
ide. After dehydrating the silica, the residue was dissolved in
dilute HC1, filtered, and made up to a volume of 100 ml.







Chemical Studies on Soils from Florida Citrus Groves 9

Calcium.-Calcium was precipitated as the oxalate in a 40 ml.
aliquot, filtered, and washed with hot water, dissolved in 10
percent H2S04 and titrated with 0.05 N KMn04. Prior to precipi-
tation of calcium, iron and aluminum if present were removed
with ammonium hydroxide.
Magnesium.-After the removal of calcium, magnesium was
precipitated as MgNH4PO4, filtered and washed with 10 percent
ammonium hydroxide. After drying, the precipitate was dis-
solved in 0.1 N H2S04 and the excess acid titrated with 0.1
N NaOH, using brom cresol green as the indicator (29).
Potassium.-An aliquot of 10 to 20 ml., depending on the
amount of potassium present, of the acid solution containing
the exchangeable bases was evaporated to dryness in the pres-
ence of a few drops of H2S04, and heated in an electric muffle
at dull redness to expel the ammonium salts and destroy the
last traces of organic matter. Potassium was then precipitated
as K2PtCI6, filtered and washed with 95 percent alcohol. The
precipitate was dissolved in hot water, and estimated colori-
metrically (13) after developing the color by the addition of
an excess of KI and making up to a volume of 100 ml.
Manganese.-A 20 ml. aliquot of the original solution was
evaporated to dryness in the presence of a few drops of H2SO4,
and ignited in an electric muffle to expel the chlorides and to
destroy the organic matter. Manganese was then extracted
with 20 ml. of 6 percent H2S04 and determined colorimetrically
(53) upon oxidation to permanganate by means of potassium
periodate.
Zinc and Copper.-Zinc and copper were determined by mak-
ing a separate extraction with 1 N NaCI solution. After
preliminary work, sodium chloride was chosen as an extracting
solution for this purpose in preference to ammonium acetate
because of the greater solvent action of ammonium salts upon
the insoluble salts (phosphates and carbonates) of zinc and
copper. In view of the small amounts of zinc and copper present
in the exchangeable form in most Florida soils it was thought
that the use of 1 N NaCl solution as an extracting reagent
should give a better measure of the supply of available zinc and
copper.
The method finally adopted was as follows. A 100-gram sam-
ple of soil was extracted with 200 ml. of 1 N NaC1 for one hour.
The supernatant liquid was carefully poured off and centrifuged.
A 100 ml. aliquot of the clear extract was evaporated to dryness






Florida Agricultural Experiment Station


after the addition of 2 ml. of 30 percent hydrogen peroxide to
destroy the organic matter. The residue was dissolved in 50 ml.
of water containing 1.5 ml. cone. HC1. After the addition of
5 ml. of 0.7 M ammonium citrate, the solution was made slightly
alkaline with ammonium hydroxide. Zinc and copper were
separated by repeated extraction with .01 percent solution of
dithizone dissolved in CCI4 according to the procedure given
by Sandell (44) which in turn is based on the work of Fisher
(23). Zinc was then separated from copper by further extrac-
tion with .01 N HCI and determined colorimetrically by means
of dithizone. The colorimetric diethyldithiocarbamate method
(21) was used in the determination of copper. All reagents
used in the determination of zinc and copper were carefully
purified. Distilled water was redistilled in Pyrex glass.
Total Nitrogen and Nitrate Nitrogen.-Total nitrogen was
determined by the Gunning-Hibbard method (2), while Harper's
(30) modification was used in the determination of the nitrate
nitrogen.
Organic Matter.-The organic matter content was determined
by loss on ignition using the official method (2).
Acid-soluble Phosphorus.-The amount of phosphorus dis-
solved in .002 N H2S04, pH 3.0 according to the method proposed
by Truog (51), was taken as a measure of the more readily-
soluble phosphorus in the soil. Due to the heterogeneous nature
of Florida light sandy soils, a larger sample of soil, 5 grams,
was used instead of 2 grams as recommended by Truog to 400
ml. of the extracting solution.
Water-soluble Phosphorus.-The water-soluble phosphorus
was determined in 1:5 soil-water extract.
Soil Reaction.-The pH value was measured by means of
the glass electrode using equal parts of soil and water.

RESULTS OF CHEMICAL ANALYSES
The amounts of calcium, magnesium, potassium, manganese,
zinc, copper, nitrate nitrogen, acid-soluble phosphorus, and
water-soluble phosphorus are expressed in pounds per acre-six-
inches of moisture-free soil (assuming 2,000,000 pounds per
acre-six-inches of soil). In view of the vast amount of existing
data on the exchangeable bases on different soil groups that
have been expressed in milli-equivalents per 100 grams, the
following conversion factors are given below to facilitate com-







Chemical Studies on Soils from Florida Citrus Groves 11

prison of the data presented here with those published in the
literature.
One 401 pounds of calcium (Ca) per acre-six-inches of soil.
milli- 243 pounds of magnesium (Mg) per acre-six-inches of soil.
equivalent 782 pounds of potassium (K) per acre-six-inches of soil.
is 549 pounds of manganese (Mn) per acre-six-inches of soil.
equivalent 654 pounds of zinc (Zn) per acre-six-inches of soil.
to 636 pounds of copper (Cu) per acre-six-inches of soil.
The total nitrogen and the organic matter are expressed as
percentages of the oven-dry soil. Approximate location, variety.
age, and general grove condition at the time of sampling are
recorded also.
The various samples within the same series have been ar-
ranged in Appendix Table 1 in the increasing order of their
exchange capacities in order to show the variation in the com-
position among the different grove soils. The minimum, maxi-
mum, and the average amounts of the various constituents found
in the different soil series are presented in Appendix Table 2.

EXCHANGE CAPACITY AND THE DEGREE OF BASE SATURATION
Exchange capacity may be defined as the capacity of a soil
to absorb and retain a certain group of plant nutrient elements
-calcium, magnesium, potassium, manganese, ammonia, zinc,
and copper-which are referred to as exchangeable bases. The
total quantity of the exchangeable bases any soil can hold is
a fixed quantity that can be varied only with difficulty, and is
determined by the amount of organic matter or clay present in
the soil. The organic matter, or more correctly, the "humus",
constitutes the main source of colloidal material in many Florida
citrus soils because of the small amounts of clay present, and
consequently the inorganic soil colloids contribute very little to
the exchange capacity. This is substantiated by the ratios of
the exchange capacity to the percent of organic matter which
remain quite constant despite the great variation of the ex-
change capacity and the amount of organic matter in these
soils. The average value of the ratio, exchange capacity/percent
of organic matter, for all the soils shown in Appendix Table 1
with the exception of six samples containing appreciable amounts
of clay was found to be equal to 2.0. Hence a unit increase in
percentage of organic matter in the soil increases the exchange
capacity approximately by 2.0 milli-equivalents per 100 grams
of soil. This would give a-value for the exchange capacity of
the soil organic matter approximately equal to 200 milli-







Florida Agricultural Experiment Station


equivalents per 100 grams which is in close agreement with
the values of exchange capacity of the organic matter in Coastal
Plain soils reported by Bartlett, Ruble and Thomas (6), as well
as in other soils reported by McGeorge (36), Mitchell (37), and
Olson and Bray (39). Some of the wide discrepancies noted in
the ratio, exchange capacity/percent organic matter, in several
samples are due to the presence of clay which would tend to
make the ratios higher. It is interesting to note that five
samples of marl-grove No. 84 sample No. 157, grove No. 87
samples No. 152 and 153, grove No. 91 sample No. 146, and
grove No. 92 sample No. 235-have much lower exchange
capacities than their textures would indicate in the field. Three
of the subsoil samples of marl, Nos. 153, 146, and 235, which had
an apparent texture of a heavy silt loam, showed an exchange
capacity of only 3.0, 6.6, and 4.1 m.e., respectively, per 100 grams.
In most of the marl samples the ratio, exchange capacity/percent
organic matter, is below 2.0, which would indicate that the ex-
change capacities of these soils is also largely determined by
their organic matter content. However, in the case of marls
containing appreciable proportions of clay, the ratios are higher
than 4.0.
One of the important factors affecting the exchange capacity
of the soil organic matter is its stage of decomposition, the
more humified portion of the organic matter having a higher
exchange capacity than the fraction that has not undergone
much decomposition. In considering the individual components
in the soil that "are responsible for base-exchange phenomena
it was thought that the presence of charcoal in some of the
samples was the cause of some of the variations observed in
the ratios of exchange capacity to the percent of organic matter.
An examination of two samples of charcoal taken from Norfolk
fine sand showed an average exchange capacity of 117 milli-
equivalents per 100 grams of material, which is considerably
lower than average for the exchange capacity of soil organic
matter. Despite some of the above difficulties, the organic
matter content affords a quick measure of the exchange capacity
in the light sandy soils, which in turn may be regarded as the
best single-value index to the relative potential fertility of the
majority of the soils planted to citrus in Florida.
The exchange capacity of the surface layer of the "blackjack-
oak land" and the poorer grades of "high pineland" usually varies
from 1.5 to 2.0 m.e., while the better grades of "high pineland"








Chemical Studies on Soils from Florida Citrus Groves 13

have an exchange capacity between 2.0 and 3.0 milli-equivalents
per 100 grams. The exchange capacity of the surface layer in
the "high-hammock land" is usually about 6.0, and about 10.0
or higher in the "low-hammock land".
It will be noted in Appendix Table 1 that the exchange capacity
of the surface layers in sandy soils is considerably higher than
that of the corresponding subsoils because of the higher organic
matter content of the surface layers. This is also reflected in
the greater amounts of exchangeable bases invariably present
in the surface layer. The total amount of exchangeable bases
such as calcium, magnesium, potassium, and manganese that a
given soil may retain in a readily available form for plant use
is not wholly determined by the exchange capacity but also the
pH, or more correctly the percent of base saturation, must be
taken into consideration. The total sum of the exchangeable
bases, excluding hydrogen, expressed as percent of the exchange
capacity is defined as percent base saturation. A soil is 100
percent base-saturated when the sum of the exchangeable cal-
cium, magnesium, potassium, manganese, and other exchange-
able bases (excluding hydrogen) is equal to the exchange
capacity. Such a soil should have a pH value of 7.0 unless
free carbonates are present, in which case the pH value is
about 8.0. At 50 percent base saturation half of the exchange
capacity of a soil is utilized by bases like calcium, magnesium,
potassium, and the other half is saturated with hydrogen which
causes soil acidity.
The relationship between the degree of base saturation of
the various soil samples presented in Appendix Table 1 and their
pH values is illustrated in Figure 1. Since by definition, base
saturation may be interpreted as the amount of base per unit
quantity of total potential soil acidity, it is evident that the
relationship shown in Figure 1 is analogous to a titration curve
obtained by titrating a weak monobasic acid with a strong base
and the following well known buffer equation may be applied,
[salt]
pH = pK + log .... (1)
[acid]
in which pK is the negative logarithm of the dissociation con-
stant of the.acid. At the point of half-neutralization, the second
term of the equation becomes zero, and the pH value is numeri-
cally equal to the pK value of the acid. Bradfield (9) calculated
the "apparent pK values" for several colloidal clays from the








Florida Agricultural Experiment Station


I per cent base aturatton
Fig. 1.-Relationship between pH value and percent of base saturation in both surface
and subsoil samples. The curve represents a theoretical titration curve of monobasic acid
having pK 5.52, which is the average apparent pK value found for all of the soil samples.
Solid dot, surface soil; circle, subsoil.

titration curves, and showed that while such a treatment was
not strictly valid, the pK values calculated from the titration
curves were in close agreement with those obtained by other
methods. Although not all of the exchangeable hydrogen is
replaced at pH 7.0 (pH of the extracting solution used), we
can apply the above relationship to base-exchange data and
evaluate the average apparent pK value. Knowing the average
apparent pK value it is possible to calculate the pH value, the
total sum of the exchangeable bases, or the exchange capacity
from any two of the three variables. Applying equation (1)
to base-exchange data,
sum of exchangeable bases excluding H
pH = pK + log .. (2)
exchangeable H
or
(sum of exchangeable bases)


(exchange capacity-sum of exchangeable bases)


pH = pK + log


. .. (3)







Chemical Studies on Soils from Florida Citrus Groves 15

At 50 percent base saturation, the observed pH is equal to the
apparent pK value or the negative logarithm of the apparent
dissociation constant of the absorbed hydrogen. From the data
on the exchange capacity, the total sum of exchangeable bases,
and the pH, the apparent pK values were calculated for the
various soil samples shown in Appendix Table 1 by means of
equation (3). The average apparent pK value was found to
be 5.52 and was used in drawing the theoretical curve in Fig-
ure 1, showing the relationship between the pH values and the
percent base saturation. There is considerable departure from
the curve of some of the experimental points, probably because
of the differences in nature of the base exchange complexes in
the different soils and the analytical difficulties encountered in
the determination of the exchangeable bases. The presence
of free fertilizer salts in the soil and the solubility of the cal-
cium, magnesium, and potassium salts of organic acids in the
extracting solution as pointed out by Bray and DeTurk (10)
would tend to give higher degrees of base saturation than the
pH values would indicate. The majority of the surface-soil and
the subsoil samples shown in Figure 1 having pH values below
5.5 showed less than 50 percent base saturation while the sam-
ples with pH values above 5.5 showed over 50 percent base
saturation. It will be noted from the curve in Figure 1 that
the base saturation is increased from 25 to 75 percent by raising
the pH value of a soil from 5.0 to 6.0. Regardless of the ex-
change capacity, a given soil may be expected to contain approxi-
mately three times as much exchangeable calcium at pH 6.0 as
at pH 5.0.
In view of the low exchange capacity of many Florida grove
soils, it seems very desirable to maintain a high degree of base
saturation by replacing hydrogen with bases like calcium and
magnesium through applications of basic materials, but any
attempt to raise the degree of base saturation to exceed a cer-
tain pH value might render zinc and manganese unavailable,
thus inducing deficiencies of these elements (17, 19, 25). The
application of basic materials to maintain the pH value of the
soil at about 6.0, which corresponds approximately to 75 percent
base saturation, is being tentatively recommended for best re-
sults. From the foregoing discussion it should be clear that
some caution should be exercised in estimating the lime require-
ment of soils from pH values alone without due consideration
to variation of exchange capacity in different soils. For years







Florida Agricultural Experiment Station


many citrus growers in Florida have been very reluctant to
make applications of any form of lime on grove soils, largely
due to over-liming injury (25) experienced prior to 1917. In
addition to this, the continuous use of acid-forming fertilizers
and the resultant increase of soil acidity below pH 5.0 have
aggravated the depletion of the less abundant elements in soils
-magnesium, manganese, zinc, and copper-to the extent that
these elements have now become the limiting factors in produc-
tion in many groves on light sandy soils. Typical examples of
the analyses of light sandy grove soils very acid in reaction
are shown in Appendix Table 1 and are discussed later in this
publication.
EXCHANGEABLE BASES
Calcium.-Since calcium is the predominating base in the
colloidal complex, the amount of exchangeable calcium found
in the various soils is closely correlated with the exchange
capacity at approximately the same pH values. For the same
reason the exchangeable calcium was found to increase with
the increasing pH values in soils having the same exchange
capacity. The effect of the pH value or the degree of base
saturation on the actual amounts of calcium and other exchange-
able bases that may be found in a surface layer of Norfolk fine
sand with an average exchange capacity of 2.5 is clearly "llus-
trated if the analysis of grove No. 28, sample No. 134, is com-
pared with that of grove No. 29, sample No. 182. As shown
in Appendix Table 2, the amount of calcium (Ca) in the surface
layer of the Norfolk soils varied from 149 to 1,240 pounds per
acre, the average amount being 520 pounds. The average cal-
cium content found for the different soil series varied from
291 to 2,717 pounds per acre in the surface layer.
Magnesium.-Bahrt (3), Bahrt and Hughes (5), Bryan and
DeBusk (12), and Tait (50) have reported evidence of marked
responses of citrus to applications of dolomite and magnesium
sulfate. The chlorotic leaf pattern due to magnesium deficiency
as it occurs under field conditions in Florida has been described
by Fudge (26) and Camp (16). Fudge (27) has recently made
a study of the chemical composition of the fruit and the foliage
and has shown that "bronzing" of citrus is definitely associated
with magnesium deficiency. The majority of the light well
drained upland soils which had not received an application of
dolomite or soluble forms of magnesium prior to the date of
sampling were found extremely deficient in magnesium, con-







Chemical Studies on Soils from Florida Citrus Groves 17

training less than 10 pounds of magnesium per acre regardless
of the exchange capacity. Symptoms of magnesium deficiency
were invariably found in groves located on such soils. Grove
soils to which considerable amounts of bonemeal had been
applied in the past contained somewhat higher quantities of
exchangeable magnesium. It should be noted here that by the
time this survey was undertaken, some of the grove soils sam-
pled had received at least one application of dolomite and upon
analysis showed a much higher magnesium content, although
the tree response to dolomite could not be noticed at the time
the samples were taken. The results of chemical analyses of
the soil samples taken from groves at the Citrus Experiment
Station, groves No. 12 and 16, in which the trees showed a
very marked response to the application of dolomite and mag-
nesium sulfate, are typical of the light sandy soils very acid in
reaction which had never received magnesium from any of the
common sources.
Many of the calcareous "low-hammock" soils were found to
be well supplied with exchangeable magnesium as revealed by
the analyses of the Parkwood soils. Trees growing on these
soils seldom show symptoms of magnesium deficiency. On the
other hand, the acid soils, such as Portsmouth, commonly asso-
ciated with Parkwood soils in "low-hammock" areas contained
much less and varying amounts of magnesium, depending upon
the exchange capacity and the fertilizer practice. The amount
of magnesium (Mg) in the surface layer of the Norfolk soils
varied from 5 to 121 pounds per acre, averaging 39 pounds. The
average magnesium content found for the different soil series
varied from 13 to 194 pounds per acre in the surface layer.
Potassium.-Although considerable variation in the amounts
of exchangeable potassium was found in soils having the same
exchange capacity, there is a general increase in the amounts
of exchangeable potassium with the increasing exchange ca-
pacity of the various soils. It should be noted also that the
exchangeable potassium content of soils having about the same
exchange capacity was usually found to increase with the in-
creasing pH values or the degree of base saturation even where
the same amounts of potash had been previously applied. The
effect of the soil reaction (pH) or the degree of base saturation
on the absorption of potassium from salts such as muriate or
sulfate of potash can be readily explained on the basis of the
position of hydrogen, calcium, and potassium in the lyotropic







Florida Agricultural Experiment Station


series. Potassium replaces calcium more readily than it does
hydrogen and consequently the efficiency of the exchange com-
plex in absorbing potassium applied in the form of salts of
strong acids is greatly increased at higher pH values because
of the greater amounts of exchangeable calcium present under
such conditions. Peech and Bradfield (42) have shown that the
amount of potassium absorbed in exchangeable form by colloidal
clay was greatly increased by increasing the degree of calcium
saturation. The above considerations would further emphasize
the importance of maintaining the proper soil reaction (pH)
and the degree of base saturation in reducing losses by leaching
not only of the common salts of potassium but other fertilizer
materials generally applied in the form of salts of strong acids,
such as magnesium sulfate, manganese sulfate, copper sulfate,
zinc sulfate, and ammonium sulfate. If comparison is made of
the small amounts of potassium found in acid sandy soils low
in exchange capacity, with an average annual application of
potash commonly used, it would seem that the loss of potassium
through leaching in such soils has been much greater than is
usually assumed. The amount of potassium (K) in the surface
layer of the Norfolk soils varied from 21 to 270 pounds per acre,
averaging 73 pounds. The average potassium content in the
surface layer of the different soil series varied from 72 to 275
pounds per acre.
Manganese.-Skinner and Bahrt (46), Skinner, Bahrt and
Hughes (47), Bahrt and Hughes (4), and Roy (43) have re-
ported beneficial effects from applications of manganese to grove
soils in Florida. The leaf symptoms of manganese deficiency
were recently described by Camp and Reuther (19) and some
of the conditions under which the deficiency of manganese has
been aggravated in both acid and alkaline citrus soils in Florida
were discussed by Camp and Peech (17) who showed that man-
ganese deficiency in citrus is found throughout the Florida grow-
ing areas on both acid and alkaline soils. These observations
of the widespread occurrence of manganese deficiency are further
confirmed in this study by the fact that the majority of the
soils examined were found to contain only small amounts of
manganese, usually less than three pounds of exchangeable
manganese per acre in the surface layer regardless of exchange
capacity. From the limited number of groves examined it is
impossible to say whether such small amounts of manganese
are adequate to meet the requirements of citrus but it should







Chemical Studies on Soils from Florida Citrus Groves 19

be pointed out that distinct leaf symptoms of manganese defi-
ciency were observed in a large number of groves on soils con-
taining this amount of exchangeable manganese in the surface
layer.
It is interesting to note that the grove soil, sample No. 251
(grove No. 47) to which manganese sulfate had been applied,
represents one of the few samples containing a larger amount
(17 pounds) of exchangeable manganese. There is no relation
between the exchangeable manganese content and the pH values
in the case of light sandy soils, although it should be noted that
two of the grove soils (groves No. 43 and 67) which had previ-
ously received large applications of lime contained less than one
pound of manganese per acre. However, the manganese con-
tent of the calcareous low-hammock soils was found to be closely
correlated with the pH value regardless of the previous man-
ganese treatments. The soil samples taken from groves No.
84, 87, 91 and 92 are typical of the so-called "marl spots" usually
found in the cabbage-palmetto-hammock soils where the marl
layer lies close to the surface or has been mixed with the surface
layer in ridging or mounding the trees. Frenching due to zinc
deficiency and pronounced symptoms of manganese deficiency
are usually associated with these soils, or the combination of
the two symptoms sometimes locally referred to as "marl french-
ing".
Samples No. 142-4 and No. 145-6 were taken from two ad-
joining groves, Nos. 85 and 91, planted at the same time and
under the same management. The surface layer (sample No.
142) of the profile in grove No. 85 consisted of 8 inches of dark
loamy fine sand, underlain by 10 inches of dingy brown fine sand
(sample No. 143) which changed abruptly into a very plastic,
slightly mottled yellowish clay (sample No. 144) about 6 inches
in thickness resting upon marl and calcareous rock. The trees
in this grove were in excellent condition and some of the finest
groves in the low-hammock areas were found on soils having
similar profiles. The surface layer (sample No. 145) taken from
the adjoining grove, No. 91, in which the trees showed symp-
toms of both zinc and manganese deficiencies, consisted of 6
inches of very dark to almost black sandy loam, underlain im-
mediately by a grayish to creamy white layer of marl (sample
No. 146). Although the surface layer in this type of profile as
found in many other groves is strongly alkaline, about pH 8.0,
the reaction of the surface layer in similar undisturbed profiles







20 Florida Agricultural Experiment Station

is somewhat acid, usually about pH 6.0. The higher pH value
of the surface layer in grove soils immediately underlain by
marl at a depth of 8 to 10 inches is undoubtedly due to mixing
of the marl layer with the surface layer in the process of ridging
or mounding the trees. The reaction of the surface layer of
grove soils having a profile similar to that found in grove No.
85 is seldom above pH 6.0 and in some cases may be as low as
4.8 as shown by sample No. 272, grove No. 82, in which case the
marl layer was 3 feet below the surface. The marl and cal-
careous rock in this type of profile is usually 2 feet below the
surface, underlying a heavy plastic layer of clay, the lower part
of which contains some marl. It should be noted that although
considerably more manganese sulfate had been applied to the
soil in grove No. 91 than in the adjoining grove No. 85, the
surface layer (sample No. 142) in grove No. 85 with a pH value
of 5.4 showed upon analysis nine times as much exchangeable
manganese as the surface layer (sample No. 145) in grove No.
91 having a pH value of 7.8. That manganese is subject to
rapid oxidation and precipitation into unavailable forms in soils
having pH values about 8.0 is borne out by the fact that the
soil, sample No. 157, grove No. 84, which had received an appli-
cation of manganese sulfate at the rate of 300 pounds per acre
for three consecutive years prior to sampling showed only 0.8
pound of manganese in the exchangeable form at time of sam-
pling. Since the manganese applications were made over a
circular area around the tree, the material was actually concen-
trated in this area probably at the rate of 1,000 pounds per acre.
It is obvious, therefore, that nothing can be gained from very
heavy applications of manganese salts on marl soils at any one
time in the correction of manganese deficiency, but smaller and
more.frequent applications should prove more efficient. In view
of the cost of the large amounts of manganese that must be
applied to such soils, it is more economical to resort to man-
ganese sprays in the correction of manganese deficiency on marl
soils.
Copper.-Although the use of copper in the correction of
exanthema of citrus, also known in Florida as diebackk" and
ammoniationn", dates back to 1910 (24), no attempt has been
made to correlate the occurrence of this physiological disorder
with the available copper content of the soil. Dieback and
ammoniation are often induced by excessive fertilization with







Chemical Studies on Soils from Florida Citrus Groves 21

nitrogen and both soil applications of bluestone and copper
sprays are used as corrective treatments.
As shown in Appendix Table 1 the amount of copper found
in the different soils regardless of the exchange capacity was
usually less than 0.5 pound per acre in the surface layer where
no copper had been recently applied. Grove soils that had re-
ceived an application of copper sulfate during the past few
years prior to sampling invariably showed a higher content of
exchangeable copper. The soil in grove No. 17, sample No. 158,
showing 4.0 pounds of copper per acre in the surface layer had
been treated with copper sulfate at the rate of 2.5 pounds per
tree one year before the samples were taken. Copper sulfate
was also applied to the soil in grove No. 44 at the rate of 4
pounds per tree during the year before the samples were taken
and this is reflected in the higher copper content of the surface
layer containing 2.6 pounds of copper per acre-six-inches. There
is some evidence that copper is either fixed into non-exchangeable
forms or readily lost through leaching. The trees in grove No.
62, which showed at one time severe symptoms of dieback and
ammoniation, had received three applications of bluestone at the
rate of 2 pounds per tree for each application during the three-
year period prior to sampling but only 0.04 pound per acre of
exchangeable copper was found in the surface layer when the
samples were taken. A noteworthy observation in this case is
that the trees did not respond to the soil application of copper,
which is rather unusual since both soil applications and copper
sprays are usually equally effective on acid sandy soils. Accord-
ing to information obtained from the grower the trees in grove
No. 22 had never been treated with copper (sprays or soil appli-
cations), yet when the samples were taken the trees in this
grove were in excellent condition, apparently free from the usual
symptoms of copper deficiency. The amount of copper found
in the surface soil was only 0.36 pound per acre which would
indicate that under proper management and fertilization, espe-
cially with regard to the use of nitrogen, the amount of copper
necessary for the proper growth of citrus is probably less than
one pound per acre, according to the method of analysis used
here. In view of the widespread use of copper as a fungicide
in the control of melanose and scab, much of the copper is prob-
ably supplied in this form. Therefore, no further attempt will
be made to correlate the copper content of the soils examined







Florida Agricultural Experiment Station


in this survey with the occurrence of symptoms of copper de-
ficiency.
Zinc.-Camp (14, 15), Camp and Reuther (18, 19), and others
(20, 35, 38, 40, 49) have shown that zinc can be used effectively
in the control of "frenching" or "mottle-leaf" in citrus. During
the past few years many of the groves that had been severely
affected with frenching have been brought back into production
following a zinc spray. As shown by Camp and Reuther (19),
frenching of citrus occurs in Florida most commonly on acid
sandy soils (below pH 5.0) very low in exchange capacity, as
well as on calcareous or over-limed soils. They concluded that
zinc has been depleted in acid sandy soils as a result of leaching
and fixed into unavailable form in alkaline soils. However,
no studies were made of the amount of available zinc present
in the various soils.
It is evident from Appendix Table 1 that the majority of the
soils examined contained 3 to 5 times as much zinc as copper,
although there was considerable variation in the amounts of
zinc ranging from 0.16 to 1.6 pounds per acre in the surface
layer in groves which had not received any soil applications of
zinc materials. There was no significant difference in the ex-
changeable zinc content among the various soil series regardless
of the exchange capacity or the organic matter content. How-
ever, the poorer grades of well drained upland soils having
exchange capacities below 2.0 and which had been maintained
very acid in reaction, below pH 5.0, over a period of time in-
variably contained less than 0.5 pound of zinc per acre in the
surface layer. Typical chemical analyses of such grove soils
are illustrated by samples taken from groves No. 1, 2, 3, 26,
and 30, in which trees showed symptoms of zinc deficiency at
the time of sampling. It has been reported previously by Floyd
(25) and Camp and Reuther (19) that frenching may be readily
induced by over-liming, and in view of the fact that trees grow-
ing on calcareous soils are frequently affected with frenching,
it would appear that zinc is fixed and rendered unavailable in
soils by lime above a certain pH value. These observations are
further substantiated by the recent investigations of Lott (34)
who showed that the toxicity of large applications of zinc oxide
to the soils could be inhibited by liming to raise the pH values
to 6.2. It is interesting to -note that.soils (groves No. 43, 56,
and 67) which had been heavily limed at one time contained
less than 0.2 pound of zinc per acre in the surface layer. Trees






Chemical Studies on Soils from Florida Citrus Groves 23

in these groves showed pronounced symptoms of zinc deficiency
at the time of sampling. It will also be noted that 11 out of
15 surface samples of Parkwood soils with a reaction of pH
6.0 to 8.3, with only two exceptions, showed less than 0.2 pound
of zinc per acre. On the other hand, four of the remaining
Park~wood soils having pH values below 6.0 in the surface layer
contained a higher amount of zinc ranging from 0.3 to 2.2 pounds
per acre. It has been already stated that trees are commonly
affected by zinc and manganese deficiencies on these soils. Ap-
parently zinc is fixed at pH values above 6.0, whereas the oxida-
tion and precipitation of manganese begins above pH 7.0 and
proceeds very rapidly in soils at pH 8.0.
The trees in groves No. 21, 29, and 32 were treated with zinc
sulfate at the rate of 50 pounds per acre one year prior to sam-
pling. It will be noted that the surface samples from these
groves contained the highest amounts of zinc found in the sur-
vey, ranging from 2 to 5 pounds per acre. Since an application
of 50 pounds of zinc sulfate (36 percent metallic zinc) is equiva-
lent to 18 pounds of metallic zinc, the above recovery after one
year is as good as might be expected on this type of soil. Jones,
Gall, and Barnette (32) have reported studies on the fixation
of zinc in several different Florida soils. Their results, however,
showing recoveries of zinc applied as zinc sulfate to a Norfolk
sand at different periods of time during the year following th(
application, as well as the amounts of exchangeable zinc found
in the untreated soils, are much higher than those presented
here. It would appear, therefore, that the ineffectiveness of
soil applications of zinc sulfate as compared to the zinc spray
method of treatment in the correction of frenching on light
sandy soils as reported by Camp (14, 15), and Camp and Reuther
(18, 19) cannot always be attributed to leaching or fixation of
zinc into non-exchangeable forms. In their experiments on the
correction of frenching in citrus, they found that, in the case
of light sandy soils, soil applications even at the rates of 5 to
10 pounds per tree were not so effective as the zinc spray method
of treatment. The failure of soil applications of zinc sulfate to
correct frenching may be due, in some cases at least, to the
inability of the trees to utilize zinc added to the soil because
of the poor root system of the affected trees, an explanation
that has been recently advanced by Chandler (20).
From the above considerations it is obvious that any recent
soil applications of zinc made prior to the date of sampling






Florida Agricultural Experiment Station


would be reflected in the analysis and would tend to obscure
any relationship between the amounts of zinc found in the grove
soils examined and the occurrence of frenching. In many in-
stances it was difficult to ascertain whether zinc had been used
in the spray program or included in the mixed fertilizer; hence,
any further correlation of the zinc content of the soils examined
with the occurrence of frenching will be dispensed with in this
publication. There is a good indication, however, that frenching
is caused by a deficiency of available zinc in the soil and that
the range between what may be considered an adequate amount
and a deficiency is probably very narrow.

ORGANIC MATTER
The organic matter content was determined by loss on igni-
tion, a quick and an accurate method for use in light sandy
soils. Since the majority of the sandy soils of Florida contain
fragments of charcoal, especially at lower depths, the more
tedious dry and wet combustion methods are likely to give high
results, especially so if the conventional Van Bemmel6n factor
1.724 is used in converting the organic carbon to organic matter.
The samples that were known to contain free carbonates were
treated with ammonium carbonate after the ignition in order
to correct for the loss in weight due to decomposition of car-
bonates.
Results of determinations of the organic matter content are
shown in Appendix Table 1, expressed as percent of the oven-
dry soil. For purposes of comparison, 1 percent of organic
matter, or any constitutent, in a soil is equivalent to about 20,000
pounds per acre-six-inches of soil. It will be noted that there
is considerable variation in the organic matter content among
the various soil groups, or within the same soil series. The
organic matter content of the Norfolk soils varied from 0.8 to
2.6 percent for the surface soils and from 0.4 to 1.4 percent for
the subsoils, although the amounts of organic matter found in
the subsoils were more or less constant (about 0.6 percent) in
the majority of the Norfolk soils examined. Organic matter
content of Eustis soils varied in the same manner. Blanton
soils contained somewhat higher amounts of organic matter than
the Norfolk soils... In general, the organic matter content of the
poorly drained soils was higher than that of the well drained
group. One surface sample of Parkwood loam, grove No. 91,
contained as much as 10 percent organic matter.






Chemical Studies on Soils from Florida Citrus Groves 25

The relationship between the exchange capacity and the or-
ganic matter content has been already discussed. The exchange
capacity, as well as the total amount of exchangeable bases,
was found directly related to the organic matter content in the
majority of soils examined. The higher exchange capacity,
and consequently the greater amounts of exchangeable bases of
the surface soils as compared with the corresponding subsoils,
can be attributed also to the differences in the relative amounts
of organic matter. In addition to its base-exchange properties
and moisture-holding capacity, the organic matter upon decom-
position liberates nitrogen, calcium, magnesium, potassium,
phosphorus, and other plant nutrient elements. The carbonic
acid formed resulting from the decomposition of the organic
matter increases the hydrolysis of the exchangeable bases and
helps to bring into solution the more insoluble minerals and
compounds in the soil.

TOTAL NITROGEN, NITRATE NITROGEN, AND THE C/N RATIO
As might be expected, total nitrogen content was found closely
re'ated to the amount of organic matter, as shown in Appendix
Table 1. It has been reported by many investigators that the
carbon/nitrogen ratio of the soil organic matter, or the humus,
is about 10 within narrow limits depending upon climatic condi-
tions and soil type. However, Anderson and Byers (1) reported
a wide divergence among the C/N ratios of different great soil
groups. They also showed considerable variation of the C/N
ratio with depth. Hosking (31), working with Australian soils,
found that the C/N ratio is a specific property of a soil under
natural and undisturbed conditions, but that upon cultivation
there is a greater loss of carbon than nitrogen, which results
in a narrowing of the ratio. The C/N ratio, therefore, may be
considered an important characteristic of the soil organic matter
and is more or less indicative of its stage of decomposition.
In calculating the C/N ratios given in Appendix Table 1, the
organic carbon was obtained by dividing the organic matter
content as determined by loss on ignition by the conventional
factor 1.724. While this procedure may not give the absolute
values for the C/N ratios, as obtained by the direct determina-
tion of the organic carbon, because of the uncertainty of the
conversion factor, the C/N ratios calculated in this manner can
be used as an index to the relative decomposition of the organic
matter in the various soils examined. It will be noted that






Florida Agricultural Experiment Station


while there is a wide variation in the C/N ratios among the
various samples shown in Appendix Table 1, the ratios of the
surface samples remain fairly constant within a given soil series.
The subsoil samples invariably showed higher and more variable
ratios, probably due to fragments of charcoal which were usually
found at lower depths in many of the light sandy soils examined.
As shown in Appendix Table 2, the average C/N ratio of the
surface samples is very nearly constant for the Norfolk, Blan-
ton, and Eustis soils, being approximately 23. The mean value
of the C/N ratio in the surface layers is 18 for Lakewood soils,
35 for both Orlando and Gainesville, 19 for Portsmouth, and
15 for Parkwood soils. Leighty and Shorey (33) have also
reported a wide variation in the C/N ratio in a number of Coastal
Plain soils. The 10 Norfolk profiles taken from Florida, South
Carolina, and Virginia gave variable C/N ratios ranging from
7 to 26 in the surface layer. The soils reported in this study,
especially those in the Orlando and Gainesville series, seem to
have a higher C/N ratio than is usually found in the cultivated
soils of the great soil groups. Whether the high C/N ratio of
these soils may be interpreted as denoting the presence of a large
quantity of decomposable organic matter or other highly car-
bonaceous material, such as charcoal, remains to be investigated.
There is no consistent relationship between the C/N ratio of
the organic matter and its exchange capacity (per unit weight)
as given by the ratio, exchange capacity/percent organic matter.
It was thought desirable to make the determination of nitrate
nitrogen to see if the amount of organic matter or its C/N ratio
has any influence upon the formation of nitrates in the soil.
As shown in Appendix Table 1, there is no apparent relationship
between the amount of organic matter, the C/N ratio and the
nitrate nitrogen content. Since the amount of nitrate nitrogen
is subject to wide seasonal fluctuations, and is readily affected
by leaching following heavy rains, as well as by fertilization,
a single determination of the nitrate nitrogen in this case would
hardly justify drawing any conclusions. It should be pointed
out, however, that three of the Parkwood soils, groves No. 84,
87, and 91, having C/N ratios of from 12 to 14, contained from
about 100 to 375 pounds of nitrate nitrogen per acre in the sur-
face layers.
The decomposition of the plant material and the formation
of ammonia and nitrate nitrogen following, for example, the
plowing under of summer cover crops is also intimately asso-






Chemical Studies on Soils from Florida Citrus Groves 27

ciated with the C/N ratio of the plant material incorporated
with the soil. Bell (7) has made a study of the comparative
rate of decomposition of several leguminous and non-leguminous
cover crops in Norfolk sand with and without the addition of
inorganic fertilizers in which he found a striking difference in
the rate of nitrate accumulation from the various organic ma-
terials. It is generally accepted that if the C/N ratio is low
as in the case of leguminous crops, ammonia and nitrate nitro-
gen will appear in the soil in excess of that required by the soil
microorganisms for body synthesis. On the other hand, if the
C/N ratio of the plant material is high the oxidation of the
carbon will likely take place at the expense of the available soil
nitrogen so that there may be actually a temporary depression
in the amount of ammoniacal and nitrate nitrogen in the soil
following the incorporation of plant material low in nitrogen.
In either case the C/N ratio of the material will be narrowed
and will tend to approach the C/N ratio of the soil, the value
of which is more or less constant for a given set of climatic
and soil conditions.
It is obvious, therefore, that the decomposition of the plant
material and its subsequent effect on the accumulation of the
organic mi-ater and nitrates in the soil is influenced by the C/N
ratio of the plant material. Upon decomposition only a small
portiontof'the total plant material added goes to increase the
organic matter or the humus content of the soil. In addition to
the climatic factors favoring rapid decomposition of the soil
organic matter in light sandy soils of Florida, the practice of
intensive fertilization with complete fertilizers has, no doubt,
expedited the rate of depletion of the soil organic matter.
Despite the difficulties attendant in building up the amount of
organic matter in well drained light sandy soils under Florida
conditions, the practice of growing and turning under of sum-
mer cover crops should at least help to maintain the initial
content of organic matter as shown by Stokes, Barnette, Jones,
and Jefferies (48). In their studies of the effects of summer
cover crops (Crotalaria striata, velvet beans, beggarweed, and
cowpeas) on the soil organic matter as well as on the tree
growth and fruit yield, they found that the organic matter con-
tent in the clean-culture plot decreased by one-third during the
seven-year period of the experiment. There was also a definite
correlation between the quantity of cover crops grown and the
growth and fruit yield of the trees.






Florida Agricultural Experiment Station


ACID-SOLUBLE AND WATER-SOLUBLE PHOSPHORUS
In contrast to the determination of exchangeable bases, meth-
ods that have been proposed for determination of the readily
available phosphorus in soils are largely empirical, since phos-
phate is not exchangeable. While more recent investigations (45)
have shown that phosphate is absorbed to some extent through
anionic exchange by some inorganic soil colloids, it is unlikely
that much of the available soil phosphorus exists in this form in
the light sandy soils of Florida. It is generally considered that
the reverted tri-calcium phosphate is more readily available than
iron or aluminum phosphate. Consequently various acids-
nitric, hydrochloric, sulfuric, acetic, citric, carbonic-of different
strengths as well as alkaline salts, such as potassium carbonate,
have been used to determine the nature and the availability of
phosphorus in soils. Although a considerable amount of in-
formation has been gained regarding the availability of different
forms of phosphorus in soils, the results obtained by such em-
pirical methods are only relative and their use in predicting
the need for phosphate fertilization must necessarily be estab-
lished upon proper correlation with plant response. Among
the methods proposed for the determination of the readily avail-
able phosphorus in soils, the .002 N H2S04 method developed
by Truog (51) has been widely used in this country. Davis
and Scarseth (22) found a high degree of correlation between
the amount of readily soluble phosphorus as obtained by Truog's
method and the crop yields in a number of Alabama soils, in-
cluding 22 representative Norfolk soils. Bryan (11) has re-
ported that there is an accumulation of available phosphorus
in old citrus groves on light sandy soils of Florida as measured
by the method of Truog. The amount of water-soluble phos-
phorus dissolved in 1:5 aqueous extracts was also higher in
the surface soil in old seedling and budded groves than in young
groves.
Truog's method slightly modified was used to determine the
amount of readily soluble phosphorus in the present study.
Because of the heterogeneous nature of Florida light sandy soils,
it is difficult to weigh out a representative 2-gram sample of
soil as recommended by Truog. For this reason, a larger sam-
ple, 5 grams, was extracted with 400 ml. of the extracting solu-
tion. Upon careful checking it was found that this deviation
did not affect results except in cases where the amount of
phosphorus was unusually high (over 2,500 pounds P per acre).






Chemical Studies on Soils from Florida Citrus Groves 29

The amount of readily soluble phosphorus as determined by
this method is designated as "acid-soluble" P in Appendix
Table 1. It should be noted that while this method has been
used successfully in evaluating the amount of readily soluble
phosphorus in acid soils it is not adapted to calcareous soils
because of the poor buffer capacity of the extracting solution.
This should be borne in mind in the interpretation of the data
presented for Parkwood soils containing a large excess of cal-
cium carbonate. The water-soluble phosphorus was determined
in 1:5 soil-water extracts. It was necessary to flocculate some
suspensions of subsoils containing appreciable amounts of clay
with sodium sulfate in order to obtain clear aqueous extracts.
TABLE 1.-THE VARIATION IN THE AMOUNT OF ACID-SOLUBLE PHOSPHORUS
OF THE SURFACE SAMPLES OF 93 GROVE SOILS.
Phosphorus 0- 50- 100- 200- 300- 400- 600- 800-11000-11500-
lbs. per acre 49 99 199 1 299 399 599 799 999 | 1499 | 2000
Number of j
Groves ....... 8 7 14 17 13 17 9 1 6 1

From Appendix Table 1 it will be noted that the acid-soluble
phosphorus of the surface samples varied between wide limits
ranging from 10 to 1,800 pounds per acre. As shown in Table 1
in which the groves have been arbitrarily grouped into 10 classes
in accordance with the amount of phosphorus found in the sur-
face soil, the acid-soluble phosphorus content was less than 100
pounds in 15 grove soils, between 100 and 600 pounds in 61
grove soils, and over 600 pounds in 17 grove soils. The amount
of acid-soluble phosphorus was usually much higher in the
surface-soil samples than in the corresponding subsoil samples,
but there is a general increase in the amount of phosphorus in
the subsoils with the increasing amount of phosphorus in the
corresponding surface soils. It is interesting to note that in
three different soils- Portsmouth, Parkwood, and Bladen
(groves No. 74, 81, and 93)-collected in the vicinity of Bra-
denton, the amount of phosphorus was found to increase with
depth. The high phosphorus content of these soils was found
to be associated with a highly mottled bluish clay in the subsoil
containing a large amount of acid-soluble and water-soluble phos-
phorus. Apparently a highly phosphatic material had been
deposited with the clay and has now become more or less distrib-
uted throughout the profile. With the exception of the above
soils, however, the amount of acid-soluble phosphorus was in-







Florida Agricultural Experiment Station


variably higher in the surface layer than in the corresponding
subsoil which would indicate that the readily soluble phosphorus
content has been increased by fertilization. In Figure 2 the
2000


1800 ---


1600 -- --


0


S1200
0

0 '000
o
5-
0
b Booo

2
a

S 80
3 o


___ ___ff1___ ___ ___ 177


600


400


200

0 o 8
0 0 G I Q)1 _<_

5 I0 15 20 25 30 35 40 45 50 bS
Age- Years
Fig. 2.-Relation of the amounts of acid-soluble phosphorus found in the
surface soils to ages of the groves.
amounts of acid-soluble phosphorus in the surface samples were
plotted againstthe ages of the respective groves. In a general
way, the acid-soluble phosphorus content in the case of the
surface soil samples is related to the age of the grove. How-
ever, several notable exceptions are apparent in Figure 2 which
would indicate that the rate of accumulation of phosphorus in
different grove soils is not constant but probably varies with
soil type and other factors. That the capacity of different soils
to fix phosphate varies greatly depending upon chemical com-
position (calcium, iron, and aluminum content) and soil reaction
is well known. The exact nature of the phosphorus, soluble in
.002 N H2S04 according to the Truog method, that has apparently


o
t
D







Chemical Studies on Soils from Florida Citrus Groves 31

accumulated in some of the grove soils, as well as the soil con-
ditions under which phosphorus is "fixed" into comparatively
readily soluble form, are not known at present. It has been
shown by Gaarder (28), Benne, Perkins, and King (8), and
others that the reversion of phosphate to tri-calcium phosphate
proceeds in soils only at high pH values. Since the majority
of the grove soils examined had been maintained probably below
pH 5.5, it is reasonable to assume that there has been little
reversion of the soluble phosphate applied as superphosphate.
Hence, it is not likely that the acid-soluble phosphorus represents
the reverted tri-calcium phosphate. This apparent accumula-
tion of phosphorus in readily soluble form in some of the grove
soils can hardly be attributed to fixation by iron and aluminum
either, since iron and aluminum phosphates are only slightly
soluble in .002 N H2S04 (52). In fact, repeated tests showed
only traces of soluble iron in the .002 N H2S04 extracts. Some
of the preliminary studies (to be published later) of factois
affecting the accumulation of readily soluble phosplhorus in
grove soils have shown that different sources of phosphate com-
monly used have different residual effects as determined by
Truog's method.


200 400 600 800 1000 1200 1400 1600 1800 2000
Acid-Soluble Phosphorus Pounds Per Acre
Fig. 3.-Relation of water-soluble phosphorus to acid-soluble phosphorus in the
surface samples of grove soils.






Florida Agricultural Experiment Station


The amount of water-soluble phosphorus varied from 0 to 36
pounds per acre in the surface layer. As shown in Figure 3
there is an apparent relationship between the water-soluble
and the acid-soluble phosphorus in the surface samples. On
the other hand, the amount of water-soluble phosphorus bears
no relation to the amount of acid-soluble phosphorus in the
case of\subsoils. It should be noted, however, that as a rule
the amount of water-soluble phosphorus in the subsoil is usually
higher in groves showing a high content of acid-soluble and
water-soluble phosphorus in the surface layer. It is obvious,
therefore, that there is a downward movement of water-soluble
phosphorus in soils showing a large amount of acid-soluble phos-
phorus in the surface layer. The amounts of phosphorus dis-
solved in 1:5 soil-water extracts are not related to the pH values
of the soils, except in the case of calcareous samples which
showed only traces of water-soluble phosphorus.
It is evident from the foregoing discussion that the supply
of readily soluble phosphorus in the light sandy grove soils of
Florida has been appreciably increased in some cases by use of
phosphatic. fertilizers. While the exact nature and the avail-
ability of the phosphorus as measured by the .002 N H2S04
method has not been established, the large amounts of water-
soluble phosphorus found in some of the groves showing high
acid-soluble phosphorus content would indicate that it should
be readily available. Reasons for wide differences in the
amounts of acid-soluble phosphorus found among the different
groves soils are obscure but probably involve a number of factors
such as soil type, soil reaction, chemical composition of the soil,
as well as the sources of phosphorus used.' It should be men-
tioned here that the various experimental plots at the Citrus
Experiment Station now containing widely different amounts of
acid-soluble phosphorus in the soil throw little or no light as
to the significance of the varying amounts of phosphorus found
in the soil. Although the trees on soils containing the larger
amounts of phosphorus are in better condition than those on
soils having the smaller amounts of phosphorus, the present
differences in the tree condition in these plots are primarily
due to other factors. Until such time as the symptoms of
phosphorus deficiency and phosphorus toxicity, if the latter con-
dition actually exists, are identified and the specific effects of
phosphorus on the growth of the tree, as well as on the yield
and the quality of the fruit, are more thoroughly understood







Chemical Studies on Soils from Florida Citrus Groves 33

it will be impossible to attach much practical significance to
the wide differences in the amounts of acid-soluble phosphorus
found in different grove soils.

COMPARISON OF SOME GROVE SOILS WITH THE
ADJOINING VIRGIN SOILS
Only four samples of virgin soils adjoining groves No. 2, 19,
54, and 72 were included for comparison and are designated
as 2V, 19V, 54V, and 72V, respectively, in Appendix Table 1.
It will be noted that both the organic matter content and the
exchange capacity are higher in three of the grove soils than
in the corresponding virgin soils. Although the total nitrogen
content has been increased, the values of the C/N ratios
have decreased as a result of fertilization and cultivation. The
amounts of calcium, potassium, acid-soluble phosphorus, water-
soluble phosphorus, and nitrate nitrogen also have been increased
by fertilization. The significance of the differences in the chemi-
cal composition observed between these grove soils and the ad-
joining virgin soils cannot be ascertained from the limited num-
ber of comparisons available in this study.

GENERAL DISCUSSION
It has been shown already that the base-exchange property
of the majority of Florida grove soils is largely due to organic
matter. Hence the problem of building up and maintaining the
organic matter in light sandy soils should be of primary im-
portance in any program of soil management. Not only is the
exchange capacity the best single-value index to the fertility
of the various soil types planted to citrus but it determines,
within narrow limits, the total amount of exchangeable bases
(calcium, magnesium, potassium) that can be maintained in
the soil with a given fertilizer practice and management. This
is well illustrated by the samples of Norfolk sand taken from
groves No. 1, 2, 3, and 4 (Appendix Table 1) which represent
the poorest grade of Norfolk soils and are typical of what is
locally called "blackjack-oak land". One of the surface samples,
No. 292, grove No. 2, already showing 64 percent base satura-
tion and a pH value of 6.2, actually contains smaller amounts
of exchangeable bases than the better grade of Norfolk soils
having an exchange capacity about 3.0 and much lower pH
values. In many instances, abrupt variations in the exchange







Chemical Studies on Soils from Florida Citrus Groves 33

it will be impossible to attach much practical significance to
the wide differences in the amounts of acid-soluble phosphorus
found in different grove soils.

COMPARISON OF SOME GROVE SOILS WITH THE
ADJOINING VIRGIN SOILS
Only four samples of virgin soils adjoining groves No. 2, 19,
54, and 72 were included for comparison and are designated
as 2V, 19V, 54V, and 72V, respectively, in Appendix Table 1.
It will be noted that both the organic matter content and the
exchange capacity are higher in three of the grove soils than
in the corresponding virgin soils. Although the total nitrogen
content has been increased, the values of the C/N ratios
have decreased as a result of fertilization and cultivation. The
amounts of calcium, potassium, acid-soluble phosphorus, water-
soluble phosphorus, and nitrate nitrogen also have been increased
by fertilization. The significance of the differences in the chemi-
cal composition observed between these grove soils and the ad-
joining virgin soils cannot be ascertained from the limited num-
ber of comparisons available in this study.

GENERAL DISCUSSION
It has been shown already that the base-exchange property
of the majority of Florida grove soils is largely due to organic
matter. Hence the problem of building up and maintaining the
organic matter in light sandy soils should be of primary im-
portance in any program of soil management. Not only is the
exchange capacity the best single-value index to the fertility
of the various soil types planted to citrus but it determines,
within narrow limits, the total amount of exchangeable bases
(calcium, magnesium, potassium) that can be maintained in
the soil with a given fertilizer practice and management. This
is well illustrated by the samples of Norfolk sand taken from
groves No. 1, 2, 3, and 4 (Appendix Table 1) which represent
the poorest grade of Norfolk soils and are typical of what is
locally called "blackjack-oak land". One of the surface samples,
No. 292, grove No. 2, already showing 64 percent base satura-
tion and a pH value of 6.2, actually contains smaller amounts
of exchangeable bases than the better grade of Norfolk soils
having an exchange capacity about 3.0 and much lower pH
values. In many instances, abrupt variations in the exchange







Florida Agricultural Experiment Station


capacity were observed within the same soil type in the same
grove. Such variations were often markedly reflected in the
tree condition, especially where no adjustment had been made
in the fertilizer practice. The effect of the variation of the
exchange capacity upon the content of exchangeable bases is
clearly depicted if we compare the analyses of the samples taken
from two adjoining groves, No. 5 and 53, at approximately the
same pH values. The general appearance of the trees in grove
No. 5 was very poor, while those in the adjacent grove, No. 53,
were in excellent condition and apparently free from any of the
common deficiency symptoms, although both groves had received
identical fertilizer treatment under the same management. It
would be futile to attempt to maintain the same amounts of
calcium, potassium, and magnesium, for example, in both of
these grove soils because simple calculations show that the sum
total of the exchangeable bases in the surface sample No. 200,
grove No. 53, exceeds the total exchange capacity of the surface
sample No. 198, grove No. 5, by 1.9 milli-equivalents per 100
grams. In order to minimize losses through leaching following
heavy rainfalls in soils having such low exchange capacities
(from 1.5 to 2.0 m.e.) it would seem necessary to make smaller
but more frequent applications of fertilizers. The effect of the
exchange capacity on the general grove condition, as shown in
Appendix Table 1, has been rather accentuated in the present
study by a number of limiting factors such as magnesium,
manganese, zinc, and copper deficiencies, which of course were
especially pronounced in groves on soils having low exchange
capacities and low pH values (below 5.0). With the increasing
use of these elements and the maintenance of a higher degree
of base saturation by a careful control of the pH value of the
soil, the differences in the grove conditions due to variations in
the exchange capacity may be largely overcome.
Importance of the maintenance of organic matter content in
light sandy soils is further emphasized if we compare exchange
capacities and amounts of exchangeable bases in surface sam-
ples with those found in corresponding subsoil samples. During
the course of sampling it was observed that most of the fine
fibrous roots were present in the surface layer usually from
4 to 6 inches in depth, and that only a few fibrous roots pene-
trated into the yellow, gray, or grayish-white subsoil immediately
below the surface layer. This limited distribution of the fibrous
roots, probably due to great differences in chemical composition







Chemical Studies on Soils from Florida Citrus Groves 35

between the surface layer and the subsoil, is a serious drawback
during periods of drouth when the trees suffer severely from
lack of moisture.
In addition to exchange capacity, variation in depth to clay
beds in the case of light sandy soils has a very decided influence
on the grove condition, other factors remaining constant. It
was observed in several instances that in places where the clay
was within 3 to 4 feet of the surface the trees appeared to be
in much better condition than where the depth to clay was more
than 7 feet. The beneficial effect of the clay at a depth of 3
to 4 feet is probably due to better moisture conditions and the
greater efficiency of the fertilizer materials applied, since losses
by leaching may be expected to be somewhat reduced under such
conditions.
Problems associated with poorly drained soils along the East
and West Coasts are somewhat more variable. Groves on "low-
hammock" soils in which the marl layer lies either near the
surface or has been mixed with the surface layer in the process
of mounding or ridging the trees cause considerable trouble
because of manganese and zinc deficiencies. The lack of proper
drainage, and salt injury arising from salt water overflow and
high salt content of irrigation waters (artesian wells) present
some of the other important problems in the East and West
Coast areas.
While in several instances during the course of discussion of
the chemical data on the various soils, reference has been made
to the general grove condition as well as to the specific deficiency
symptoms, the information compiled thus far is considered in-
adequate for the purpose of establishing correlations and no
conclusions are being drawn regarding the optimum amounts
of the various nutrient elements in the soil necessary for the
proper growth of citrus. Further and more specific investiga-
tions along these lines in regard to some of the elements are
now being carried on.,

SUMMARY
A chemical study was made of approximately 100 soils col-
lected from groves in the important citrus areas of the state
and covering a wide range of grove conditions on representative
soil types. The chemical analyses included the determination
of the exchange capacity; percent base saturation; exchangeable
calcium, magnesium, potassium, manganese, zinc, and copper;







Florida Agricultural Experiment Station


acid (.002 N H2S04) -soluble phosphorus; water-soluble phos-
phorus; total nitrogen; nitrate nitrogen; organic matter (loss
on ignition); and soil reaction (pH). The chemical data pre-
sented show the variations in composition among the different
soil samples within the same series, as well as the minimum,
the maximum, and the average amounts of the various constit-
uents found in the different soil series. Results of analyses and
some of the inferences drawn are briefly summarized below.
The well drained upland soils of the state that are most ex-
tensively planted to citrus, commonly known as "blackjack
lands" and "high pinelands", including Norfolk, Blanton, Eustis,
and Lakewood series, have a very low exchange capacity, usually
between 2 and 3 milli-equivalents per 100 grams. The base-
exchange property of these soils is largely determined by their
organic matter content as shown by the constancy of the ratios,
exchange capacity/percent organic matter. The exchange ca-
pacity increased approximately by 2.0 m.e. per unit increase
in the percentage of organic matter. It was found that the
exchange capacity affords the best single-value index to the
relative potential fertility of the various soils planted to citrus.
The average value for the exchange capacity of the different
soil series varied from 2.7 to 8.6 milli-equivalents per 100 grams
in the surface layer.
A fair general relationship was found between the degree of
base saturation and the pH values in both surface and subsoil
samples showing a wide variation in exchange capacity. .From
the data on the exchange capacity, total sum of exchangeable
bases, and the pH, the average pK value of both the surface
and the subsoil samples examined was calculated to be 5.5,
which was found closely equal to the pH value at 50 percent
base saturation. In order to provide an adequate supply of
exchangeable bases in soils having such low exchange capacity,
and to minimize losses by leaching of fertilizer materials applied
in the form of salts of strong acids, it is highly desirable to
maintain a high degree of base saturation by the addition of
some form of basic material. The use of sufficient basic ma-
terials to maintain the soil reaction at about pH 6.0, which
corresponds approximately to 75 percent base saturation, is
being tentatively recommended for best results.
Most of the light sandy soils examined were found very de-
ficient in magnesium, manganese, zinc, and copper. / The small
amounts of these elements found may be attributed to the low







Chemical Studies on Soils from Florida Citrus Groves 37

levels existing in the virgin soils and to the fact that up to the
present time they have been added in insufficient amounts to
meet grove needs. This deficiency has been further aggravated
by the excessive losses due to leaching as a result of continuous
.use of acid-forming fertilizers without the correction of the
resultant increase of soil acidity. As a result these elements
have become limiting factors in production in many groves. In
many instances the amount of exchangeable magnesium found
was less than 10 pounds per acre where this element had not
been applied. The majority of the samples contained approxi-
matey- 3 pounds of exchangeable manganese, 1 pound of zinc,
and 0.5 pound of copper per acre-six-inches in the surface layer.
When compared with the amounts of these elements commonly
applied to the soil in correcting the deficiencies, the above
amounts found seem exceedingly low.
The use of phosphatic fertilizers has, in some cases, definitely
increased the amount of readily soluble phosphorus in the soil.
Most grove soils were found to contain from 100 to 600 pounds
of readily soluble phosphorus as determined by Truog's method.
In a general way, the acid-soluble phosphorus content in surface
soil samples was related to the age of the grove. The amount
of water-soluble phosphorus was found to increase with the
increasing amount of acid-soluble phosphorus in the surface
layer. Although the exact nature and the availability of the
accumulated phosphorus have not been established, the large
amounts of water-soluble phosphorus found in some of the grove
soils showing a high content of acid-soluble phosphorus would
indicate that it should be readily available.
A wide variation in C/N ratio was found to exist among the
different series with average values varying from 15 to 35, but
within any given series the ratios were quite constant./ Whether
the high C/N ratio of these soils may be interpreted to denote
the presence of a large quantity of decomposable organic matter
or other highly carbonaceous material such as charcoal which
was usually found, especially at lower depths, remains to be
investigated.








38 Florida Agricultural Experiment Station

LITERATURE CITED

1. ANDERSON, M. S.. and H. G. BYERS. The carbon nitrogen ratio in
relation to soil classification. Soil Sci. 38: 121-138. 1934.
2. Assoc. OF OFF. AGR. CHEMISTS. Official and tentative methods of
analysis. Assoc. of Off. Agr. Chemists, Washington, D. C., Fourth
Ed. 1935.
3. BAHRT, G. M. Progress report of soil fertility and fertilizer experi-
ments on bronzing of citrus. Proc. Fla. State Hort. Soc. 47: 18-20.
1934.
4. BAHRT, G. M., and A. E. HUGHES. Recent developments in citrus soil
fertility investigations. Proc. Fla. State Hort. Soc. 48: 31-38. 1935.
5. BAHRT, G. M., and A. E. HUGHES. Soil fertility and experiments on
bronzing of citrus. Proc. Fla. State Hort. Soc. 50: 23-28. 1937.
6. BARTLETT, J. B., R. W. RUBLE and R. P. THOMAS. The influence of
hydrogen peroxide treatments on the exchange capacity of Mary-
land soils. Soil Sci. 44: 123-138. 1937.
7. BELL, CHARLES E. Rate of decomposition of organic matter in Norfolk
sand as measured by the formation of carbon dioxide and nitrates.
Jour. Agr. Res. 50: 717-729. 1935.
8. BENNE, E. J., A. T. PERKINS and H. H. KING. Effect of calcium ions
and reaction upon the solubility of phosphorus. Soil Sci. 42: 29-38.
1936.
9. BRADFIELD, RICHARD. Some chemical reactions of colloidal clay. Jour.
Phys. Chem. 35: 360-373. 1931.
10. BRAY, R. H., and E. E. TURK. Field method for lime requirement of
soils. Soil Sci. 32: 329-341. 1931.
11. BRYAN, O. C. The accumulation and availability of phosphorus in
old citrus grove soils. Soil Sci. 36: 245-260. 1933.
12. BRYAN, O. C., and E. F. DEBUSK. Citrus bronzing-a magnesium
deficiency. Florida Grower 44(2): 6, 24. 1936.
13. CAMERON, F. K., and G. H. FAILYER. The determination of small
amounts of potassium in aqueous solutions. Jour. Amer. Chem. Soc.
25: 1063-1073. 1903.
14. CAMP, A. F. The use of zinc sulphate on citrus. Citrus Industry
15(10): 16, 18. 1934.
15. CAMP, A. F. Zinc sulphate as a soil amendment in citrus groves.
Proc. Fla. State Hort. Soc. 47: 33-38. 1934.
16. CAMP, A. F. Symptomatology of deficiencies and toxicities of citrus.
Proc. Fla. State Hort. Soc. 51: 145-150. 1938.
17. CAMP, A. F., and MICHAEL PEECH. Manganese deficiency in citrus in
Florida. Proc. Amer. Soc. Hort. Sci. 36: 81-85. 1938.
18. CAMP, A. F., and WALTER REUTHER. Progress in zinc sulphate studies.
Proc. Fla. State Hort. Soc. 48: 59-61. 1935.








Chemical Studies on Soils from Florida Citrus Groves 39

19. CAMP, A. F., and WALTER REUTHER. Studies on the effect of zinc and
other unusual mineral supplements on the growth of horticultural
crops. Fla. Agr. Exp. Sta. Ann. Rept. 1937: 132-135. 1937.
20. CHANDLER, W. H. Zinc as a nutrient for plants. Bot. Gaz. 98(4):
625-646. 1937.
21. COULSON, E. J. Report on copper. Jour. Assoc. Off. Agr. Chem.
20: 178-188. 1938.
22. DAVIS, F. L., and G. D. SCARSETH. Some correlations between crop
yields and the readily available phosphorus in soils as determined
by Truog's method. Jour. Amer. Soc. Agron. 24: 909-920. 1932.
23. FISHER, HELLMUT. Dithiozonverfahren in der chemischen Analyse.
tiberblick fiber die Entwicklung der letzten Tahre. Z. Angew. Chem.
50: 919-932. 1937.
24. FLOYD, B. F. Dieback treatments (Dieback experiments). Fla. Agr.
Exp. Sta. Ann. Rept. 1910: 70-71. 1910.
25. FLOYD, B. F. Some cases of injury to citrus trees apparently induced
by ground limestone. Fla. Agr. Exp. Sta. Bul. 137: 161-179. 1917.
26. FUDGE, B. R. Magnesium deficiency in relation to yield and chemical
composition of seedy and commercially seedless varieties of grape-
fruit. Proc. Fla. State Hort. Soc. 51: 34-43. 1938.
27. FUDGE, B. R. Relation of magnesium deficiency in grapefruit leaves
to yield and chemical composition of fruit. Fla. Agr. Exp. Sta.
Bul. 331: 1-36. 1939.
28. GAARDER, TORBJORN. Die Bindung der Phosphorsiure im Erdboden
Vestlandets Forst. Forsoks-Sta. Meddel. 14. 1930.
29. HANDY, J. O. The volumetric determination of magnesia. Jour.
Amer. Chem. Soc. 22: 31-39. 1900.
30. HARPER, HORACE J. The accurate determination of nitrates in soils.
Jour. Ind. and Eng. Chem. 16: 180-183. 1924.
31. HOSKING, J. S. The carbon-nitrogen ratios of Australian soils. Soil
Research 4: 253. 1935.
32. JONES, H. W., O. E. GALL and R. M. BARNETTE. The reaction of zinc
sulfate with the soil. Fla. Agr. Exp. Sta. Bul. 298: 1-43. 1936.
33. LEIGHTY, W. R., and E. C. SHOREY. Some carbon-nitrogen relations
in soils. Soil Sci. 30: 257-266. 1930.
34. LorT, W. L. The relation of H-ion concentration to the availability
of zinc in the soil. Proc. Soil Sci. Soc. Amer. 3: 115-121. 1938.

35. MATHEWS, I. The zinc sulfate treatment for mottle-leaf of citrus
trees in the Sundays River Valley. Citrus Grower 41: 30-32. 1935.
36. MCGEORGE, W..T. The base exchange property of organic matter in
soils. Ariz. Agr. Exp. Sta. Tech. Bul. 30. 1930.








Florida Agricultural Experiment Station


37. MITCHELL, J. The origin, nature, and importance of soil organic
constituents having base-exchange properties. Jour. Amer. Soc.
Agron. 24: 256-275. 1932.
38. MOWRY, HAROLD, and A. F. CAMP. A preliminary report on zinc
sulphate as a corrective for bronzing of tung trees. Fla. Agr.
Exp. Sta. Bul. 273: 1-34. 1934.
39. OLSON, L. C., and R. H. BRAY. The determination of the organic
base-exchange capacity of soils. Soil Sci. 45: 483-496. 1938.
40. PARKER, E. R. Experiments on the treatment of mottle-leaf of citrus
trees. Proc. Amer. Soc. Hort. Sci. 31: 98-107. 1934.
41. PEECH, MICHAEL. Chemical composition of Florida citrus soils. Citrus
Industry 19(6) : 5, 9, 16, 17, 20, 21. 1938.
42. SPEECH, MICHAEL, and RICHARD BRADFIELD. The effect of lime and
neutral calcium salts upon the solubility of soil potassium. Amer.
Soil Survey Assoc. Bul. 15: 101-106. 1934.
43. RoY, W. R. The effect of soil applications of manganese on the
mineral composition of foliage and maturity of fruit in citrus. Proc.
Fla. State Hort. Soc. 50: 29-37. 1937.
44. SANDELL, E. B. Determination of copper, zinc, and lead in silicate
rocks. Jour. Ina. and Eng. Chem. Anal. Ed. 9: 464-469. 1937.
45. SCARSETH, G. D. The mechanism of phosphate retention by natural
alumino-silicate colloids. Jour. Amer. Soc. Agron. 27: 596-616. 1935.
46. SKINNER, J. J., and G. M. BAHRT. Trend of fertilizer practice with
reference to citrus culture in Florida. Proc. Fla. State Hort. Soc.
44: 4-7. 1931.
47. SKINNER, J. J., G. M. BAHRT and A. E. HUGHES. Influence of fertil-
izers and soil amendments on citrus trees, fruit production and
quality of fruit. Proc. Fla. State Hort. Soc. 47: 9-17. 1934.
48. STOKES, W. E., R. M. BARNETTE, H. W. JONES and J. H. JEFFERIES.
Studies on summer cover crops in a Pineapple orange grove. Fla.
Agr. Exp. Sta. Bul. 253: 1-18. 1932.
49. STRICKLAND, A. G. Mottle-leaf of citrus-preliminary note on correc-
tion in South Australia with zinc sprays. Jour. Dept. Agr. S.
Australia 40: 579. 1937.
50. TAIT, W. L. Some field tests with magnesium sources. Proc. Fla.
State Hort. Soc. 49: 9-14. 1936.
51. TRUOG, E. The determination of the readily available phosphorus of
soils. Jour. Amer. Soc. Agron. 22: 874-882. 1930.
52. TRUOG, E. Present status and future of soil testing and soil analysis.
Proc. Soil Sci. Soc. Amer. 2: 181-183. 1937.
53. WILLARD, H. H., and L. GREATHOUSE. Colorimetric determination of
manganese by oxidation with periodate. Jour. Amer. Chem. Soc.
39: 2366-2377. 1917.








APPENDIX


TABLE 1.-CHEMICAL ANALYSES OF THE MAJOR CITRUS GROVE SOILS OF FLORIDA.

I I o Pounds per acre-six-inches of soil2 g
W C; S SExchangeable Bases P o 6 I 0


SP JA j Q ) g 4 E 1
0 5h c c .5 55~A~
P) en X~c E~r U m~ l~ o


1 290 0-5 6.06
291 5-18 5.30

2292 0-5 6.25
293 5-18 4.96

2V 294 0-5 5.21
295 5-18 5.31

3 296 0-5 5.86
291 5-18 4.96

4 330 0-6 4.96
301 6-18 4.38

5 198 0-6 6.25
199 6-18 5.10

6 306 0-6 6.25
307 6-18 5.01

7 143 0-5 5.39
141 5-18 5.09


293 6-18 4.29

9 124 0-6 6.30
125 6-18 4.85


88 7
22 3

160 7
32 2

0 1
0 0

307 8
32 3

227 9
32 1

229 6
58 2

227 9
48 7

176 9
32 2

480 14
80 6

272 10
32 2


0.023
0.010

0.022
0.008

0.021
0.008

0.025
0.011

0.028
0.012

0.020
0.008

0.028
0.007

0.024
0.008

0.028
0.010

0.032
0.009


Babson
Park

Frost-
proof

Frost-
proof

Frost-
proof

Daven-
port

Apopka


Way-
erly

Lake
Wales

Daven-
port

Avon
Park


Seedy 18 P
Gft.

Valencia 15 P
0.

SVirgin -
Soil

Valencia 18? P
0.

Pineapple 13 P
0.

Pineapple 18 P
0.

Valencia 20 E
0.

Valencia 14 P
0.

Seedy 23 P
Gft.

Pineapple 20? G
O. e


'The following abbreviations are used in soil type: s.-sand, f.-fine, v.-very.
2Based on 2 million pounds per acre-six inches of soil.
TThe following abbreviations are used in evaluating the general grove condition:. (P)-poor, (F)-fair, (G)-good, (E)-excellent.
N.D.-not determined.


Norfolk
s.

Norfolk
s.

Norfolk
S.

Norfolk
s.

Norfolk
s.

Norfolk
f. s.

Norfolk
s.

Norfolk
f. s.

Norfolk
s.

Norfolk
f. s.


I











TABLE 1.-CHEMICAL ANALYSES OF THE MAJOR CITRUS GROVE SOILS OF FLORIDA-Continued.


Q 0


Norfolk 10
f. s.
o .


Norfolk 11
f. s.

Norfolk 12
f. s.

Norfolk 13
f. s.

Norfolk 14
f. s.

Norfolk 15
f. s.

Norfolk 16
f. s.


Norfolk 17
f. s.


Norfolk 18
f.

Norfolk 19
f. s.
Norfolk 19
f. s.


Norfolk 20
s.

Norfolk 21
f. s.


Exc
a
&0
U
.0
a "
B\5


hanged


able Bases P


Z a
0S 0
1 N 5I


6-18 5.01

0-6 5.26
6-18 5.01

0-6 4.80
6-18 4.75

0-6 6.20
6-18 4.85

0-5 5.55
5-18 5.19

0-5 6.15
5-18 4.85

0-6 4.79
6-18 4.75

0-6 5.14
6-18 4.80

0-6 4.95
6-18 4.61

0-8 5.09
8-18 4.54

0-6 4.84
6-18 5.41

0-7 5.20
7-18 5.36

0-5 4.85
5-18 4.56


.&- .."6
1S l.
&< o a p


o 0




25 Lake
37 Wales

25 Uma-
36 tilla

28 Lake
36 Alfred

19 Avon
36 Park

17 Plym-
26 outh

21 Alturas


0.031
0.009

0.023
0.009

0.024
0.007

0.038
0.009

0.036
0.010

0.026
0.009

0.024
0.008

0.026
0.010

0.030
0.009

0.036
0.010

0.019
0.007

0.025
0.010

0.031
0.011


I Valencia
0.

Tangerine

SPineapple
0.

Pineapple
0.

Seedling
0.

Valencia
0.

Pineapple
0.

Pineapple
0.

Valencia
0.

Pineapple
0.

Virgin
Soil

Hamlin
0.

Temple
0.


G 2.

P
tea

P




P
P


P
p 3.








P



P




E
s-


35 5
16 0.5

176 10
48 3


Lake
Alfred

Uma-
tilla

Daven-
port

Lees-
burg

Lees-
burg

Lees-
burg

Lees-
burg


I I


, --- --- .


4 ,









TABLE 1.-CHEMICAL ANALYSES OF THE MAJOR CITRUS GROVE SOILS OF FLORIDA-Continued.


a 6
a Z
a a
?I s
M 0
1 C;I
z2 I


Norfolk s.
(hammock
phase)

Norfolk
f. s.

Norfolk
s.

Norfolk.
s.

Norfolk
f. s.

Norfolk
f. s.

Norfolk
f. s.

Norfolk
.f. s.
Norfolk
f. s.

Norfolk
f. s.

Norfolk
f. s.

Norfolk
f. s.


s?
a,
'5 a
a .0
a a
B N


33 1 249 1 0-6 1 6.05 | 72.0 | 2.70
250 1 6-181 5.34 1 13.3 1 0.93


Exchangeable Bases P

l I i


700 1 29
36 I 2


L


' '


I I I


11.6 1.60
3.0 0.80

3.0 0.56
0.4 0.32

1.8 0.48
0.1 0.32

1.7 0.24
0.1 ND

2.1 0.40
0.4 0.24

1.8 0.32
0.2 0.24

2.3 0.48
0.7 0.48

2.8 2.40
1.8 0.32

2.1 0.48
0.3 0.24

4.7 0.64
0.9 0.32

4.1 3.20
1.5 0.32

1.2 0.32
0.1 0.24


0.36 592 15
0.14 64 |13


0.24 294 8
0.18 32 1

0.94 240 10
1.40 48 8

0.60 400 I 9
ND 48 6

0.08 600 13
0.06 70 7

0.80 388 110
0.36 64 | 5

0.24 304 J14
0.16 80 | 8

0.12 198 111
0.10 42 2

0.26 154 111
0.16 71 3

0.16 368 13
0.12 48 2

0.08 16 7
0.08 32 1

0.34 362 | 8
0.24 48 4


0 1 i O ig P4 e >


17 0.042 1.27 1.74 18 Min- Parson
6 0.016 0.66 2.14 24 neola Brown (

22 0.045 1.41 1.64 18 Avon Pineapple
10 0.008 0.57 1.20 41 Park O.

3 0.034 1.33 1.78 23 Way- Valencia
3 0.008 0.44 1.91 32 early O.

5 0.036 1.45 1.64 23 Way- I Valencia
2 0.007 0.59 1.27 49 erly I 0.

8 0.038 1.33 1.82 20 Gotha Valencia
2 0.012 0.65 1.97 31 0.

11 0.043 1.47 1.66 20 Apopka Valencia
1 0.010 0.50 2.06 29 0.

4 0.038 2.21 1.11 34 Lake Valencia
0 0.011 0.60 2.07 32 Wales O.

0 0.033 1.37 1.82 24 Lees- Temple
0 0.011 0.64 2.02 34 burg O.

26 0.039 1.41 1.77 21 Dade Seedy
12 0.012 0.65 2.08 31 Ci y | Gft.

5 0.039 1.61 1.56 24 Lake Valencia
1 0.012 0.61 1.69 29 Wales O.

9 0.039 1.73 1.48 26 Lees- Hamlin
4 0.013 0.95 1.45 42 burg 0.

15 0.045 1.70 1.59 22 Sebring Valencia
0 0.009 0.70 1.83 45 0.











TABLE 1.-CHEMICAL ANALYSES OF THE MAJOR CITRUS GROVE SOILS OF FLORIDA-Continued.


:hangeable Bases


Norfolk
f. s.

Norfolk
f. s.

Norfolk
f. s.

Norfolk
f. s.

Norfolk
f. s.

Norfolk
f. s.

Norfolk
f. s.

Norfolk
f. s.

Norfolk

f. s.

Norfolk
f. s.


Norfolk
f. s.
Norfolk

f. s.
f. s. |


I


0-6 I 6.14
6-181 4.71

0-5 5.14
5-18 4.69

0-5 5.84
5-18 4.44

0-5 6.35
5-18 5.69

0-6 I 5.81
6-181 5.19

0-6 1 5.45
6-181 4.75

0-6 4.96
6-18 5.04

0-7 5.49
7-181 4.69

0 5 5.35
5-1 4.75

0-6 I 6.49
6-18 5.89

0-6 4.64
6-1 4.40

0-7 5.24
7-18 5.34

0-6 1 5.75
6-18 4.64


Exc
| ----,--


r8



2.90 1100 76
1.11 105 11

2.96 500 21
1.81 76 3

2.99 705 67
1.64 63 6

3.10 1010 I 57
1.32 212 13

3.10 655 I 24
1.47 93 3

3.19 567 64
1.27 36 6

3.21 735 35
1.20 118 6

3.37 595 46
1.27 50 5

3.40 428 63
1.50 35 6

3.43 1280 56
1.15 142 15

3.48 356 14
1.90 45 2

3.63 305 27
1.65 96 27

3.68 1220 95
1.05 100 11


---


'


3.0 0.40
0.7 0.48

3.2 0.40
1.5 0.32

1.8 0.32
0.4 0.40

6.0 0.48
2.1 0.32

2.1 0.32
0.3 0.24

2.8 0.64
0.8 0.56

14.7 2.40
1.7 0.64

1.6 1.10
1.0 0.32

4.3 1.20
1.5 0.64

0.3 0.08
0.1 0.16

2.4 0.80
0.7 0.48

4.3 0.40
0.8 0.08

3.0 0.32
0.6 0.24


------------


P
p e


s .



0.44 1160 13 35 0.053
0.12 93 1 12 0.009

0.30 390 16 13 0.042
0.36 86 13 3 0.031

0.48 735 114 77 0.048
0.40 118 110 18 0.013

S0.64 1080 112 9 0.053
0.16 122 8 3 0.014

0.56 500 12 13 0.046
0.14 80 4 2 0.014

0.18 368 11 2 0.042
0.12 64 5 0 0.013

0.18 400 16 57 0.051
0.12 93 8 5 0.010

0.24 400 17 6 0.039
0.18 87 115 0 0.009

0.08 482 11 11 0.040
0.08 70 3 6 0.010

0.36 304 112 11 0.058
0.06 58 3 0 0.010

2.60 187 13 20 0.045
0.12 42 0 9 0.014

0.08 72 5 9 0.041
0.04 6 0 0 0.012

0.40 1480 18 39 0.058
0.12 100 11 10 0.009


.s z







1.67 1.74 18 Lucerne Seedy
0.43 2.58 28 Park Gft.

1.70 1.74 23 Lees- Valen
0.80 2.26 15 burg 0.

1.50 2 00 18 Uma- Pinea
0.66 2.48 29 tills 0.

1.68 1.85 18 Apopka Seedlil
0.70 1.88 29 0.

1.53 2.02 19 Gotha Valen
0.76 1.94 31 0.

1.70 1.88 23 Lake Valen
0.75 1.70 33 Wales O.

1.70 1.89 19 Plym- Seedli
0.59 2.03 34 south 0.

1.80 1.88 27 Lake Valen
0.51 2.50 33 Alfred 0.

1.88 1.81 27 Uma- Pineal
0.82 1.83 48 tilla 0.

2.13 1.61 21 Cocoa Pineal
0.60 1.92 35 0.

2.16 1.61 28 Winder- Pineal
1.03 1.85 43 mere O.

2.43 1.50 34 Lees- Hamli
1.25 1.35 60 burg 0.

1.93 1.91 19 Lucerne Seedy
0.43 2.44 28 Park Gft.


cia


pple

ng

cia


cia


ng

cia


pple

apple

pple

n


P

P


P
P 3.




P
p a


P

G


G
Z*
G


p I








TABLE 1.-CHEMICAL ANALYSES OF THE MAJOR CITRUS GROVE SOILS OF FLORIDA-Continued.


E_ Exchangeable Bases P

a; z
a a ..
I E a 1
13 -- Q -Z 8
0 A P P4 z


Norfolk
f. s.
Norfolk
f. s.
Norfolk
f. s.
Norfolk
f. s.
Norfolk
f. s.
Norfolk f.s.
(hammock
phase)
Norfolk f.s.
(hammock
phase)
Norfolk
f. s.

-':orfolk f.s.
(hammock
phase)
Norfolk
v. f. s.

Blanton
f. s.
Blanton
f. s.


47 251
252
48 130
131
49 247
248
50 278
279

51 128
129
52 186
187

53 200
201

54 220
221

54V 222
223

55 284
285

56 310
311
57 168
169


0-9
9 18
0-7
7-18


5.45 80.2
5.10 45.8
5.69 60.0
4.99 14.6
5.51 80.8
4.76 26.1
5.66 65.0
4.75 22.5
5.16 49.5
4.90 18.1

5.66 64.0
4.85 21.3

6.35 68.5
5.21 16.0

4.90 17.5
4.54 7.0

5.55 20.0
5.81 15.1

5.29 32.5
5.05 12.7

6.19 68.5
5.04 7.6
5.90 63.0
5.39 25.5


1840 125 24
131 11 7
320 14 3
48 3 0
760 29 31
128 14 4
1040 19 8
128 15 0

272 21 4
80 5 1

608 [21 26
144 122 5

326 ]10 5
96 2 9

150 | 4 18
16 I 0.5 13
49 3 0
42 1 0

290 |19 6
80 J 1 0

200 110 8
40 3 2

625 118 15
112 117 0


I


2.03 1.82
0.62 2.00
1.91 1.98
1.04 1.77
2.47 1.54
0.61 2.70

1.97 2.02
0.86 2.16
2.31 1.75
1.08 1.83
2.07 2.10
1.08 2.41

2.24 2.21
1.40 1.88

3.10 1.61
1.35 1.41
2.53 1.76
1.66 1.65

2.62 2.39
1.45 2.10

1.99 1.77
0.91 2.33

1.45 2.58
0.65 2.74


o r
0l >

Winter Valencia
Haven I O.

Lake Valencia
Wales 0.
Cocoa Valencia
0.
Lake I Valencia
Alfred I 0.
Lake Valencia
Wales 0.
Cler- Seedling
mont 0.

Ocoee Pineapple
0.

Dade Seedy
City Gft.
Dade Virgin
City Soil

Home- Valencia
land O.

Auburn- Seedy
dale Gft.

Uma- Seedling
tilla 0.


'---


.


o

-o
ccci



a '0
G







F

G

P
G










- -



E
co


P E

E
P C











TABLE 1.-CHEMICAL ANALYSES OF THE MAJOR CITRUS GROVE SOILS OF FLORIDA-Continued.


0



Blanton
f. s.
Blanton
f. s.
Blanton
f. s.
Blanton
f. s.

Eustis
f. s.
Eustis
f. s.
Eustis
f. s.
Eustis
f. s.
Eustis f. s.
(dark-
colored
phase)

Lakewood
f. s.

Lakewood
f. s.

Orlando
f. s.


& a

0-6 5.84
6-18 4.71
0-6 5.54
6-18 4.59
0-6 5.54
6-18 4.49
0-6 I 5.49
6-18 5.16

0-6 5.64
6-1 5.09

0-7 6.20
7-1 5.50
0-6 6.39
6-18 5.74
0-7 6.29
7-18 5.56.
0-8 5.69
8-18 5.00



0-6 6.00
6-12 5.54
12-18 4.54
0-7 6.74
7-18| 6.04

0-6 I 5.46 [
6-18| 5.19


Exchangeable Bases






70 66 2.5 1.1 0.68
8 31 0.7 0.32 0.36
22 73 0.3 0.32 0.06
2 42 0.1 0.32 0.06
78 112 3.1 0.88 0.62
11 34 0.7 0.56 0.30
49 135 5.0 0.32 0.14
3 41 1.0 0.16 0.06

34 94 2.5 0.32 0.04
6 28 1.7 0.24 0.04

54 56 3.8 0.32 0.32
19 38 4.7 0.16 0.08
51 202 8.5 0.40 0.80
14 61 3.9 0.16 0.06
83 190 1.7 0.24 0.30
13 88 1.0 0.16 0.08
59 208 2.8 1.4 0.22
7 93 1.9 0.48 0.12
1


P


d I
^U -I |^ R0 a ri|


518 [17 33 0.049 1.87 2.08 22 Uma- Pineapple 18 P
102 115 10 0.010 0.65 2.80 38 tilla 0. |

960 23 6 0.048 1.88 2.20 23 | DeLand Pineapple ? E
205 21 0 0.018 1.47 2.34 47 1 0.
735 19 39 0.057 1.85 2.26 19 Lucerne Seedy 25 P
112 1 14 0.013 0.69 2.46 31 Park Gft.
336 11 I 14 0.049 2.31 2.03 27 DeLand Hamlin 20 E
80 2 0 0.020 1.62 1.64 .47 0.

432 15 9 0.034 1.46 1.95 25 Eustis Valencia 12 P
58 5 2 0.012 0.72 2.17 35 0.
480 112 15 0.055 1.72 1.73 18 | Tavares See ling 45 G
146 111 2 0.018 0.96 2.06 31 I 0.
1480 118 7 0.060 1.58 2.10 15 Eustis Seedling 42 F
128 119 6 0.011 0.58 2.83 31 0.
760 118 11 0.067 2.37 2.22 21 Home- Seedling 55 G
120 J16 3 0.041 1.12 2.51 16 land O.

530 113 4 0.060 3.18 2.03 31 Bartow Seedling 55 E
120 0 0 0.023 2.12 1.70 53 0.



397 117 20 0.057 1.67 1.94 17 Orange Seedling 55 F
48 I 8 4 0.016 0.47 1.95 17 City 0. 0
96 7 0 0.013 0.70 2.06 31
625 115 8 0.067 2.18 2.59 19 Braden-I Valencia 20 F
246 113 0 0.017 0.86 3.04 29 ton O.

58 4 4 0.039 2.02 11.77 1 30 Orlando Pineapple 8 G
22 0 2 0.020 1.37 1.66 40 I 0.


3.24 880
0.92 101
1.44 65
5.65 2160
2.61 532

3.58 252
2.27 38







TABLE 1.-CHEMICAL ANALYSES OF THE MAJOR CITRUS GROVE SOILS OF FLORIDA-Continued.


0


Orlando
f. s.

Gainesville
f. s.
Gainesville
f. s.

. Gainesville
S s.

Portsmouth
f. s. (hard-
pan phase)
Portsmouth
f. s.

Portsmouth
f. s.
Portsmouth
f. s.
Portsmouth
f. s.

Parkwood
f. s.

Parkwood
f. s.

Parkwood
f. s.
Parkwood
f. s.


Exchangeable Bases


0
z




70


71

72

72V


73


74

75

76

77


78

79

80

81


z 4





214 0-12 5.16 15.1
215 12-24 5.00 11.3

224 0-6 5.49 38.8
225 6-18 5.20 21.7

226 0-6 5.79 41.2
227 6-18 5.36 16.6

228 0-6 6.09 39.6
229 6-18 6.09 20.8

274 0-8 4.55 42.7
275 8-18 4.36 67.5

276 0-8 5.94 86.0
277 8-18 5.51 82.5

150 0-11 5.64 66.5
151 11-24 5.30 55.5
154 0-12 5.26 55.0
155 12-18 5.06 54.5

156 0-18 5.14 62.5


270 0-10 5.24 52.8
271 10-24 5.24 77.0

261 0-7 5.74 66.8 1
262 7-14 4.81 48.7

259 0-7 6.26 89.0
260 7-14 5.70 79.5

265 0-7 6.25 96.5
266 7-14 5.41 75.0
267 14-24 6.84 100.0


440 21 58
172 13 44


1680 75
895 130
3680 1030


69 2.7
74 6.1
247 1.7


6.62 329



3.70 242

8.50 040
4.82 218

6.65 795
4.10 238


P
z e
1 I E a as .
O 0 0
u z 0; 19 A


10 106
6 56

79 250
21 84

125 300
39 72

141 52
55 26


0.057 I 4.06 1.63
0.039 I 3.12 1.45

0.075 4.36 1.63
0.022 2.66 1.39

0.086 5.50 1.55
0.033 3.68 1.31

0.066 I 4.60 1.45
0.030 I 3.10 1.32

0.047 1.52 1.94
0.012 0.55 1.45

0.061 1.58 2.34
0.033 1.41 7.80

0.046 1.87 2.00
0.011 0.53 1.65
0.054 2.14 2.56
0.011 0.56 1.54

0.124 I 3.29 2.84


0.32 0.12
0.16 0.06

0.24 0.20
0.08 0.06

0.32 0.22
0.08 0.60

0.08 0.08
0.08 | 0.06

1.4 0.16
0.96 0.08


150 2
23 0

265 5
39 0

231 4
59 0

49 3
39 1

64 39
16 11

465 120
2280 47

32 8
10 I 4

26 113
10 3

33 1


48 13
32 110
384 125
55 117
476 115
80 113

545 115
592 124
3200 33


4.75
3.82
13.2


i



Pineapple
0.

Valencia
0.
Valencia
0.

Virgin
Soil

Seedy
Gft.

Seedy
Gft.

Valencia
0.
Marsh
Gft.
Marsh
Gft.

Seedy
Gft.

SSeedy
Gft.
Seedy
Gft.

Seedy
Gft.


22


12

7


-I


25


25

18

18


41 Orlando
46 i

34 Dade
70 City
37 Dade
68 City

40 Dade
60 City

19 Pal-
27 metto

15 Braden-i
25 ton

24 Vero
28 Beach

23 Vero
30 Beach

15 Vero
Beach

18 Braden-
20 ton

15 Braden-
18 ton
14 Braden-
19 ton

16 Braden-
22 I ton


G
G





-P CO







E

P

G


E


P

G
ci.




0


Q
P Co


E














P
G
-t
G &

E


P c






G












TABLE 1.-CHEMICAL ANALYSES OF THE MAJOR CITRUS GROVE SOILS OF FLORIDA-Concluded.


I Exchangeable Bases


a



272 0-10 4.88 52.7
273 10-24 4.88 46.0

148 0-7 6.20 83.0
149 7-13 6.40 82.5
157 0-8 8.31 100.0

142 0-8 5.46 64.5
143 8-18 6.50 79.5
144 18-24 8.16 100.

147 0-12 6.26 95.0

152 0-12 8.11 100.0
153 12-18 8.20 100.0

232 0-8 6.00 82.5
233 8-18 8.29 100.
236 0-6 6.44 100.
237 6-14 6.66 100.
230 0-8 6.94 98.5
231 8-16 8.19 100.
145 0-6 7.86 100.
146 6-18 8.19 100.

234 0-6 7.81 100.
235 6-18 8.35 100.

268 0-10 5.45 69.5
269 10-24 5.86 86.5


Parkwood
f. s.
Parkwood
f. s. loam
Parkwood
clay loam
Parkwood
s. loam

Parkwood
s. loam

Parkwood
clay loam
Parkwood
f. s. loam
Parkwood
loamy f. s.
Parkwood
f. s. loam
Parkwood
loam

Parkwood
f. s. loam

Bladen
f. s. loam


P




z

96 34 6
192 17 0

144 6 22
19 1 7
13 0 97

129 9 18
20 0 6
10 0 2

88 9 24

26 0 101
10 0 8
108 111 5
13 0 4
745 126 7
109 113 11
216 111 5
10 0 4
25 I 1 375
10 0 154
214 5 38
22 0 13

1240 |36 6
3160 196 0


Braden-
ton

Vero
Beach

Vero
Beach

Vero
Beach

Vero
Beach
Vero
Beach

Wild-
wood
Titus-
ville
Wild-
wood

Vero
Beach

Titus-
ville


Seedy
Gft.
Marsh
Gft.
Marsh
Gft.

Seedy
Gft.

Valencia
0.
Seedy
Gft.

Pineapple
0.
Pineapple
0.
Parson
Brown O.

Seedy
Gft.
Pineapple
0.


5.46 985 57 148 1.5 0.48
4.05 528 86 150 0.8 0.96
5.75 1320 266 307 2.8 0.24
3.20 625 194 228 1.5 0.24
6.60 2070 284 210 0.4 0.16

6.95 1300 227 196 9.3 0.32
5.72 1210 347 93 0.8 0.32
14.0 3950 950 200 0.6 0.16

S7.68 2240 310 301 3.9 0.16

7.85 2300 465 175 1.3 0.16
3.06 725 272 113 0.4 0.16
9.00 2660 132 154 6.6 0.16
17.7 6250 445 209 0.3 0.08
11.6 4350 117 198 1.8 0.16
4.72 1760 52 67 0.6 0.08

14.7 5450 183 261 5.3 0.16
27.6 9700 750 122 0.3 0.08
17.9 6450 347 313 0.8 0.16
6.63 2200 215 195 0.3 0.16

119.3 7000 308 416 0.3 0.08
S4.10 1330 139 178 0.6 0.08

1 5.31 1215 73 250 26.6 0.56
121.6 5700 795 855 12.0 0.16


0.26
0.18
0.10
0.12
0.30
0.12
0.10
0.08
0.24
0.18
0.80
0.20

0.14
0.06


E

G
G "
ta

G




P




G

G C.

G

P


0.065 1.68 3.16 15 Braden- Valencia
0.040 2.25 9.60 33 ton 0.









TABLE 2.-MINIMUM,


MAXIMUM, AND AVERAGE AMOUNTS OF VARIOUS CONSTITUENTS FOUND IN DIFFERENT CITRUS
GROVE SOILS.


Pounds per acre-six-inches of soil |
No. of Base Exch. I Total Organic Ratio:
Soil Sam- Depth pH Satu- Cap. Exchangeable Bases P Ni- N I Matter Ex. Ratio
Series pes ration m.e. / I Acid IWater rate I % % % M. C:N
% 100 g. Ca M K Mn Zn Cu I Sol.I So]. N
Min. 4.60 17.5 1.39 149 5 21 0.2 0.08 0.06 35 4 0 0.020 0.89 1.11 17
S55 Surface Max. 6.59 100. 6.25 1240 121 270 17. 5.6 4.2 1840 29 77 0.073 3.10 2.39 34
Norfolk Soil Aver. 5.56* 57.3 2.72 520 39 73 3.2 0.91 0.55 408 12 13 0.039 1.56, 1.73 23
Min. 4.29 7.0 0.68 20 1 8 0.0 0.08 0.04 6 0 0 0.007 0.42 1.17 15
55 Subsoil Max. 5.89 48.2 3.04 212 27 68 5.3 0.96 3.0 144 22 18 0.031 1.45 2.70 60
Aver. 5.03 17.8 1.26 66 6 26 0.8 0.36 0.26 61 6 3 0.011 0.70 L84 36

Min. 5.49 40.2 3.51 605 18 66 0.3 0.16 0.06 200 10 6 0.039 1.45 2.03 19
6 Surface Max. 6.19 75.0 4.70 1070 78 175 7.5 2.0 0.68 960 23 39 0.057 2.31 2.58 29
Blanton Soil Aver. 5.75 59.4 4.02 812 47 110 3.3 0.80 0.31 566 16 19 0.047 1.90 2.23 24
Min. 4.49 7.6 1.70 40 2 31 0.1 0.16 0.04 40 2 0 0.010 0.65 1.64 31
6 Subsoil Max. 5.39 22.1 3.44 281 13 42 1.5 0.56 0.36 205 21 14 0.020 1.62 2.80 47
Aver. 4.90 17.3 2.25 126 7 36 0.8 0.32 0.15 109 12 4 0.014 1.00 2.40 40

Min. 5.64 51.2 2.84 485 34 56 1.7 0.24 0.04 432 12 4 0.034 1.46 1.73 15
5 Surface Max. 6.39 89.5 6.46 1460 83 208 8.5 1.4 0.80 1480 18 15 0.067 3.18 2.22 31
Eustis Soil Aver. 6.04- 71.5 4.17 1001 56 150 3.9 0.54 0.34 ,740 15 9 0.055 2.06 2.00 22
Min. 5.00 17.1 1.56 81 6 28 1.0 0.16 0.04 58 0 2 0.011 0.58 1.70 16
5 Subsoil Max. 5.74 64.0 3.60 363 19 88 4.7 0.48 0.12 146 19 6 0.041 2.12 2.83 53
Aver. 5.38 36.7 2.32 263 12 62 2.6 0.24 0.08 115 11 3 0.021 1.10 2.25 33

Min.' 6.00 77.5 3.24 880 54 73 0.7 0.08 0.12 397 15 8 0.057 1.67 1.94 17
2 Surface Max. 6.74 100. 5.65 2160 105 78 1.2 0.16 0.22 625 17 20 0.067 2.18 2.59 19
Lakewood Soil Aver. 6.37 88.7 4.45 1520 79 76 0.9 0.12 0.17 514 16 14 0.062 1.93 2.27 18
Min. 4.54 5.9 0.92 65 5 30 0.1 0.08 0.06 48 7 0 0.013 0.47 1.95 17
3 Subsoil Max. 6.04 33.9 2.61 532 34 57 0.1 0.40 0.10 248 13 4 0.017 0.86 3.04 31
Aver. 5.37 19.0 1.66 233 15 44 0.1 0.24 0.08 131 9 1 0.015 0.68 2.35 26

*Arithmetical average of pH values rather than of the actual hydrogen ion concentration.












TABLE 2.-MINIMUM, MAXIMUM, AND AVERAGE AMOUNTS OF VARIOUS CONSTITUENTS FOUND IN DIFFERENT CITRUS
GROVE SOILS-Concluded.

Soil No. of Base I Exch. Exchangeable Bases P i- Total Organic Rato
Series I Sam- Depth PH Sat. Cap. I IAcid Water tratel N Matter Ex.Cap. C:N
pies I Ca Mg K I Mn Zn Cu I Sol. Sol. I N I ___ %Ot.M.

Min. 5.16 15.1 3.58 252 10 37 1.5 0.32 0.06 58 | 2 4 0.039 2.02 1.63 30
2 Surface Max. 5.46 20.8 6.62 329 16 106 2.5 0.32 0.12 150 4 5 0.057 4.06 1.77 41
Orlando Soil Aver. 5.30 18.0 5.10 291 13 72 2.0 0.32 0.09 104 3 4 0.048 3.04 1.70 35:
Min. 5.00 11.3 2.27 38 3 19 1.5 0.16 0.06 22 0 I 2 0.020 1.37 1.45 40
2 Subsoil Max. 5.19 58.5 4.52 165 6 56 1.7 0.16 0.12 23 0 I 6 0.039 3.12 1.66 46
SAver. 5.10 34.9 3.40 102 5 37 1.6 0.16 0.09 23 0.2 4 0.030 2.25 1.56 43

Min. 5.49 38.8 7.10 835 79 250 2.3 0.24 0.20 231 4 14 0.075 4.36 1.55 34
2 Surface Max. 5.79 41.2 8.50 1040 125 300 3.9 0.32 0.22 265 5 | 20 0.086 5.50 1.63 37
Gainesville Soil Aver. 5.64 40.0 7.80 938 102 275 3.1 0.28 0.21 250 4 17 0.081 4.93 1.59 35
Min. 5.20 16.6 3.70 218 211 72 0.9 0.08 0.06 391 0 5 0.022 2.66 1.31 68
2 Subsoil Max. 5.36 21.7 4.82 242 39 84 1.3 0.08 0.60 59 1 7 0.033 3.68 1.39 70
Aver. 5.28 19.2 4.26 230 30 78 1.1 0.08 0.33 50 0 6 0.028 3.17 1.35 69

SMin. 4.55 42.7 2.95 440 21 58 1.1 0.16 0.12 26 1 0 0.046 1.52 1 94 15
5 Surface Max. 5.94 86.0 9.35 1860 236 171 5.1 1.4 0.24 465 20 20 0.124 3.29 2.84 24
Portsmouth Soil Aver. 5.31 62.5 5.04 1025 107 110 2.6 0.50 0.16 125 17 7 0.066 2.08 2.34 19
| Min. 4.36 54.5 0.80 148 13 19 0.5 0.16 0.06 10 3 0 0.011 0.53 1.45 25
S4 Subsoil Max. 5.51 82.5 11.0 2650 495 332 1.7 0.96 0.12 2280 47 2 0.033 1.41 7.83 30
Aver. 5.06 65.0 3.38 781 136 104 0.9 0.52 0.09 582 16 1 0.017 0.76 3.11 27


15
Parkwood 15|

13


Bladen 1


Min.
Surface Max.
Soil Aver.


Subsoil


Surface


Max.
Aver.


4.88 52.7
8.31 100.
6.52 85.4


3.62 635 16 69
19.3 7000 465 416
8.63 2717 194 206


0.3 0.08 0.08 13
9.3 2.2 1.2 745
3.2 0.45 0.30 220


4.81 46.0 1.18 304 I 24 | 37 0.3 0.08 0.06 10
8.35 100. 27.6 9700 750 228 11.5 0.96 0.20 592
6.68 83.7 6.71 2053 213 123 2.4 0.31 0.12 90
05 21 j


5.45


5.31 1215 I 73 250 27.


0.56 0.14 1240


bubsoil 5.50 21.8 0.16 0.06 1160 15100 795 815 I


15700 i 795 855
1 1 I !


6 0.065
0 1 0.040


1.68 3.16
2.25 9.60


T i I I


Subsoil


5.86


21.6


0.16 0.06 3160




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