UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
WILLARD I. FIFIELD, Director
IA Contriliution from the Citrus Experiment Station)
A Rapid Test for Possible Excesses of
Copper in Sandy Soils
W. F. SPENCER
Formerly Assistant Chemist, Citrus
Single copies free to Florida residents upon request to
AGRICULTURAL EXPERIMENT STATION
BOARD OF CONTROL
J. Lee Ballard, Chairman, St. Petersburg
Hollis Rinehart, Miami
Fred H. Kent, Jacksonville
Wm. H. Dial, Orlando
Mrs. Alfred I. duPont, Jacksonville
George W. English, Jr., Ft. Lauderdale
W. G'eni Miller, Monticello
J. B. Culpepper, Secretary, Tallahassee
John S. Alien, Acting President
J. Wayne Reitz, Ph.D., Provost for Agr.:'
Willard M. Fifield, M.S., Director
J. R. Beckenbach, Ph.D., Asso. Director
R. W. Bledsoe, Ph.D., Assistant Director
Rogers L. Bartley, B.S., Admin. Mgr.:
Geo. R. Freeman, B.S., Farm Superintendent
W. H. Jones, Jr., M.Agr., Asst. Supt.
MAIN STATION, GAINESVILLE
H. G. Hamilton, Ph.D., Agr. Economist 1
R. E. L. Greene, Ph.D., Agr. Economist
M. A. Brooker, Ph.D., Agr. Economist ',
Zach Savage, M.S.A., Economist
A. H. Spurlock, M.S.A., Agr. Economist
D. E. Alleger, M.S., Associate
D'. L. Brooke, Ph.D., Associate
M. R. Godwin, Ph.D., Associate 3
W. K. McPherson, M.S., Agr. Economist'
Eric Thor, M.S., Asso. Agr. Economist '
Cecil N. Smith, M.A., Asso. Agr. Economist
Levi A. Powell, Sr., M.S.A., Assistant 4
E. D. Smith, Ph.D., Asst. Agr. Economist
N. K. Roberts, M.A., Asst. Agr. Economist
Orlando, Florida (Cooperative USDA)
G. Norman Rose, B.S., Asso. Agr. Economist
J. C. Townsend, Jr., B.S.A., Agr. Statistician 2
J. B. Owens, B.S.A., Agr. Statistician 2
F. T. Galloway, M.S., Agr. Statistician
C. L. Crenshaw, MS., Asst. Agr. Economist
B. W. Kelly, M.S., Asst. Agr. Economist
Frazier Rogers, M.S.A., Agr. Engineer l 3
J. M. Myers, M.S.A., Asso. Agr. Engineer
J. S. Norton, M.S., Asst. Agr. Engineer
Fred H. Hull, Ph.D., Agronomisti
G. B. Killinger, Ph.D., Agronomist
H. C. Harris, Ph.D., Agronomist
W. A. Carver, Ph.D., Agronomist
Fred A. Clark, M.S., Associate
E. S. Horner, Ph.D., Assistant
A. T. Wallace, Ph.D., Assistant
D. E. McCloud, Ph.D., Associate 3
G. C. Nutter, Ph.D., Asst. Agronomist
I. M. Wofford, Ph.D., Asst. Agronomist
E. 0. Burt, Ph.D., Asst. Agronomist
J. R. Edwardson, Ph.D., Asst. Agronomist 3
ANIMAL HUSBANDRY AND NUTRITION
T. J. Cunha, Ph.D., Animal Husbandman 1
G. K. Davis, Ph.D., Animal Nutritionist :
R. L, Shirley, Ph.D., Biochemist
A. M. Pearson, Ph.D., Asso. An. Husb.'
John P. Feaster, Ph.D., Asst. An. Nutri.
H. D. Wallace, Ph.D., Asso. An. Husb.3
M. Koger, Ph.D., An. Husbandman '
J. F. Hentges, Jr., PhD., Asst. An. Huab.3
L. R. Arrington, Ph.D., Asst. An. Husb.
A. C. Warnick, Ph.D., Asst. Physiologist
E. L. Fouts, Ph.D., Dairy Techno'ogist 3"
R. B. Becker, Ph.D., Dairy Husbandman :
S. P. Marshall, Ph.D., Asso. Dairy Hush.3
W. A. Krienke, M.S., Asso. Dairy Tech.'
P. T. Dix Arnold, M.S.A., Asso. Dairy Husb.3
Leon Mull, Ph.D., Asso. Dairy Tech.'
H. H. Wilkowske, Ph.D., Asso. Dairy Tech.8
James M. Wing, Ph.D., Asst. Dairy Hush.
J. Francis Cooper, M.S.A., Editor 3
Clyde Beale, A.B.J., Editor "
William G. Mitchell, A.B.J.,Assistant Editor
H. L. Moreland, Jr., B.S.A., Asst. Editor
A. N. Tissot, Ph.D., Entomologist
L. C. Kuitert, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant
F. A. Robinson, M.S., Asst. Apiculturist
R. E. Waites, Ph.D., Asst. Entomologist
S. H. Kerr, Ph.D., Asst. Entomologist
J. R. Christie, Ph.D., Nematologist
Ouida D. Abbott, Ph.D., Home Econ.'
R. B. F-er.ch, Ph.D., Biochem'st
G. H. Blackmon, M.S.A., Horticulturist 1'
R. A. Dennison, Ph.D., Hort. & Interim Head
F. S. Jamison, Ph.D., Horticulturist 3
Albert P. Lorz, Ph.D., Horticulturist
R. K. Showalter, M.S., Asso. Hort.
R. H. Sharpe, M.S., Asso. Horticulturist
V. F. Nettles, Ph.D., Asso. Horticulturist
F. S. Lagasse, Ph.D., Horticulturist 2
R. D. Dickey, M.S.A., Asso. Hort.
L. H. Halsey, M.S.A.. Asst. Hort.
C. B. Hall, Ph.D., Asst. Horticulturist
Austin Griffiths, Jr., B.S., Asst. Hort.
S. E. McFadden, Jr., Ph.D., Asst. Hort.
C. H. VanMiddelem, Ph.D., Asst. Biochemist
B. D. Thompson, M.S.A., Interim Asst. Hort.
M. W. Hoover, M.S.A., Asst. Hort.
Ida Keeling Cresap, Librarian
W. B. Tisda'e, Ph.D., Plant Pa'hologist 3
Phares Decker, Ph.D., Plant Pathologist
Erdman West, M.S., Botanist & Mycologist.
Robert W. Earhart, Ph.D., Plant Path.2
Howard N. Miller, Ph.D., Asso. Plant Path.
Lillian E. Arnold, M.S., Asso. Botanist
C. W. Anderson, Ph.D., Asst. Plant Path.
N. R. Mehrhof, M.Agr., Poultry Hush.b'
J. C. Driggers, Ph.D., Asso. Poultry Husb.3
F. B. Smith, Ph.D., Microbiologist 3
Gaylord M. Volk, Ph.D., Soils Chemist
J. R. Neller, Ph.D., Soils Chemist
Nathan Gammon, Jr., Ph.D., Soils Chemist
Ralph G. Leighty, B.S., Asst. Soil Surveyor
G. D. Thornton, Ph.D., Microbiologist3
C. F. Eno, Ph.D., Asst. Soils Microbiologist
H. W. Winsor, B.S,A., Assistant Chemist
H. E. Caldwell, M.S.A., Asst. Chemist 3
V. W. Carlisle, M.S., Asst. Soil Surveyor
J. H. Walker, M.S.A., Asst. Soil Surveyor
William K. Robertson, Ph.D', Asst. Chemist
0. E. Cruz, B.S.A., Asst. Soil Surveyor
W. G. Blue, Ph.D., Asst. Biochemist
J. G. A. Fiskel, Ph.D., Asst. Biochemist
L. C. Hammond, Ph.D., Asst. Soil Physicist'
H. L. Breland, Ph.D.. Asst. Soils Chem.
W. L. Pritchett, Ph.D., Soil Technologist
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarian3
C. F. Simpson, D.V.M., Asso. Veterinarian
L. E. Swanson, D.V.M., Parasitologist
W. R. Dennis, D.V.M., Asst. Parasitologist
E. W. Swarthout, D.V.M., Asso. Poultry
Pathologist (Dade City)
M. Ristic, D.V.M., Associate Pathologist
J. G. Wadsworth, D.V.M., Asst. Poul. Path.
NORTH FLORIDA STATION, QUINCY
W. C. Rhoades, M.S., Entomologist in Charge
R. R. Kincaid, Ph.D., Plant Patholozist
L. G. Thompson, Jr., Ph.D., Soils Chemist
W. H. Chapman, M.S., Agronomist
Frank S. Baker, Jr., B.S., Asst. An. Hush.
T. E. Webb, M.S.A., Asst. Agronomist
Mobile Unit, Monticello
R. W. Wallace. B.S., Associate Agronomist
Mobile Unit, Marianna
R. W. Lipscomb, M.S., Associate Agronomist
Mobile Unit, Pensacola
R. L. Smith, M.S.. Associate Agronomist
Mobile Unit, Chipley
J. B. White. B.S.A.. Associate Agronomist
CITRUS STATION. LAKE ALFRED
A. F. Camp, Ph.D., Vice-Director in Charge
W. L. Thompson, B.S., Entomologist
R. F. Suit, Ph.D., Plant Pathologist
E. P. Ducharme, Ph.D., Asso. Plant Path.
J. W. Sites, Ph.D., Horticulturist
H. 0. Sterling, B.S., Asst. Horiculturist
H. J. Reitz, Ph.D., Horticulturist
F'rancine Fisher, M.S., Asst. Plant Path
I. AW. Wander, Ph.D., Soils Chemist
J. W. Kesterson, M.S., Asso. Chemist
R. Hendrickson, B.S., Asst. Chemist
Ivan Stewart, Ph.D., Asst. Biochemist
D. S. Prosser, Jr., B.S., Asst. Engineer
R. W. Olsen, B.S., Biochemist
F. W. Wenzel, Jr., Ph.D., Chemist'
Alvin H. Rouse, M.S.. Asso. Chemist
H. W. Ford, Ph.D., Asst. Horticulturist
L. C. Knorr, Ph.D., Asso. Histologist
R. M. Pratt, Ph.D., Asso. Ent.-Pathologist
W. A. Simanton, Ph.D., Entomologist
E. J. Deszyck, Ph.D., Asso. Horticulturist
C. D'. Leonard, Ph.D., Asso. Horticulturist
W. T. Long, M.S., Asst. Horticulturist
M. H. Muma, Ph.D., Asso. Entomologist
F. J. Reynolds, Ph.D., Asso. Hort.
R. B. Johnson, Ph.D., Asst. Entomologist
W. F. Newhall, Ph.D., Asst. Biochemist
W. F. Grierson-Jackson, Ph.D.. Asst. Chem.
Roger Patrick, Ph.D., Bacteriologist
M. F, Oberbacher, Ph.D., Asst. Plant Physiol.
R. C. J. Koo, Ph.D., Asst. Biochemist
J. R. Kuykendall, Ph.D., Asst. Horticulturist
W. C. Price, Ph.D., Virologist
J. J. McBride, Jr., Ph.D., Assistant Chemist
EVERGLADES STATION, BELLE GLADE
W. T. Forsee, Jr., Ph.D., Chemist in Charge
R. V. Allison, Ph.D., Fiber Technologist
Thomas Bregger, Ph.D., Physiologist
J. W. Randolph, M.S.. Agricultural Engr.
R. W. Kidder, M.S., Asso. Animal Husb.
C. C. Seale, Associate Agronomist
N. C. Hayslip, B.S.A., Asso. Entomologist
E. A. Wolf, M.S., Asst. Horticulturist
W. H. Thames, M.S., Asst. Entomologist
W. G. Genung, M.S., Asst. Entomologist
Robert J. Allen, Ph.D., Asst. Agronomist
V. E. Green, Ph.D., Asst. Agronomist
V. L. Guzman, Ph.D., Asst. Hort.
J. C. Stephens, B.S., Drainage Engineer'
A. E. Kretschmer, Jr., Ph.D., Asst. Soils
Charles T. Ozaki, Ph.D., Asst. Chemist
D. S. Harrison, M.S., Asst. Agri. Engr.
'. T. Boyd, Ph.D., Asso. Agronomist
J. N. Simons, Ph.D., Asst. Virologist
D. W. Beardsley, M.S., Asst. Animal Huslh.
R. S. Cox, Ph.D., Asso. Plant Pathologist
Donald M. Coe, Ph.D., Asst. Plant Pathologist
SUB-TROPICAL STATION, HOMESTEAD
Geo. D. Ruehle, Ph.D., Vice-Dir. in Charge
D. O. Wolfenbarger, Ph.D., EntomoloZist
Francis B. Lincoln, Ph.D., Horticulturist
Robert A. Conover, Ph.D., Plant Path.
John L. Malcolm, Ph.D., Asso. Soils Chemist
R. W. Harkness, Ph.D., Ass'c. Chemist
R. Bruce Ledin, Ph.D., Asst. Hort.
J. C. Noonan, M.S., Asst. Hort.
M. H. Gallatin, B.S., Soil Conservationist -
T. W. Young, Ph.D., Asso. Horticulturist
WEST CENTER. FLA. STA., BROOKSVILLE
Marian W. Hazen. M.S.. Animal Husband-
man in Charge 2
RANGE CATTLE STATION, ONA
W. G. Kirk, Ph.D., Vice-Director in Charge
E. M. Hodges, Ph.D., Agronomist
D. W. Jones, M.S., Asst. Soil Technologist
F. M. Peacock, M.S., Asst. An. Husbandman
CENTRAL FLORIDA STATION, SANFORD
R. W. Ruprecht. Ph.D., Vice-Dir. in Charge
J. W. Wilson, ScD., Entomologist
P. J. Westgate, Ph.D., Asso. Hort.
Ben F. Whi'tner, Jr., B.S.A., Ass t. Ho
J. F. Darby, Ph.D., Asst. Plant Path.
WEST FLORIDA STATION, JAY
C. E. Hutton, Ph.D., Vice-Director in Charge
H. W. Lundy, B.S.A., Associate Agronomist
R. L. Jeffers, Ph.D., Asso. Agronomist
SUWANNEE VALLEY STA., LIVE OAK
G. E. Ritchey, M.S.. Agronomist in Charge
GULF COAST STATION, BRADENTON
E. L. Spencer, Ph.D., Soils Chemist in Charge
E. G. Kelsheimer, Ph.D., Entomologist
David G. A. Kelbert, Asso. Horticulturist
Robert 0. Magie., Ph.D., Plant Pathologist
J. M. Walter, Ph.D., Plant Pathologist
S. S. Woltz, Ph.D., Asst. Horticulturist
Donald S. Burgis, M.S.A., Asst. Hort.
C. M. Geraldson, Ph.D., Asst. Horticulturist
G. Sowell. Jr., Ph.D.. Asst. Plant Pathologist
Watermelon, Grape, Pasture-Leesturg
J. M. Crall, Ph.D., Plant Path. in Charge
C. C. Helms, Jr., B.S., Asst. Agronomist
L. H. Stover, Assistant in Horticulture
A. N. Brooks, Ph.D., Plant Pathologist
A. H. Eddins, Ph.D., Plant Path. in Charge
E. N. McCubbin, Ph.D., Horticulturist
T. M. Dobrovsky, Ph.D.. Asst. Entomologist
D. L. Myhre, Ph.D., Asst. Soils Chemist
A. M. Phillips, B.S., Asso. Entomologist -
John R. Large, M.S., Asso. Plant Path.
Warren O. Johnson, B.S., Meteorologist in
1Head of Department
In cooperation with U. S.
SCooperative, other divisions. 1'. of F.
REAGENTS AND MATERIALS ...... .. .. -- -... ..... ..... .. (i
Leaching Solution .................. ---..... (i
Carbam ate Reagent .. .. ..... .... ........ ....--- ...... .. ....
Filter Paper .......... ..... .......... .........
Soil Sample ......................... .. ... ............... 7
RUNNING THE TEST .............. .. .....-- ....--.... -.............-- 7
INTERPRETATION OF THE TEST .... .... ............. .- ..- 9)
USE OF THE TEST ... ..... ........ ........ ---... ....--- .... 10
PERSONAL VARIATION IN APPLICATION OF THE TEST .................... 11
LITERATURE CITED ..... .. ..... .. .... ....... .. .. .. 11
A Rapid Test for Possible Excesses of
Copper in Sandy Soils
W. F. SPENCER 1
It is known that applied copper is largely retained in sandy
soils and may exhibit beneficial or harmful properties, depend-
ing on the amount present in the soil. Soil analysis by Rogers
et al. (9) showed that the copper content of virgin soils was
usually less than 10 ppm, whereas cultivated soils contained as
high as 300 ppm Cu. Erwin (4) found that less than 1%C of
the added copper was leached from lysimeters filled with soil
during the nine months of his experiments. More recent work
by Reuther, Smith, and Specht (6, 7, 8) and Westgate (15)
verified the fact that copper accumulates in Florida soils. Thus,
it is possible to build up the copper content of the soil so that
it is not necessary to apply additional copper to meet the nu-
tritional requirements of citrus trees.
It has been common practice in recent years to apply relatively
large amounts of copper to citrus grove soils. Thus, in some
groves such large accumulations of copper occur (7) as to be
potentially detrimental to citrus trees. Chapman and associates
(1) observed that slight excesses of copper induced iron chlorosis
in citrus plants growing in nutrient solutions. Reuther and Smith
(6) concluded that the level of soil copper in many mature
Florida citrus groves on acid sandy soil is approaching a point
where foliage chlorosis and damage to normal root development
is likely to occur if the soil is allowed to become too acid. Stewart
and Leonard (11) found that acid soil chlorosis of citrus can
be corrected by additions of an iron chelate (EDTA) to the soil.
Excess copper has been found to be detrimental to other crops
also. Recent work by Westgate (15) indicates that residues
from copper sprays on celery and other crops have accumulated
in toxic amounts in the surface layer of old celery fields in the
Sanford area. Steenbjerg (10) found that the amount of copper
available to grasses and cultivated plants was at a minimum
at pH 5.5 to 6.5 and that organically combined copper was avail-
able at various pH values depending upon the combination in
which it occurred. Reuther and Smith (6) and Westgate (15)
1The author wishes to thank Dr. Herman J. Reitz for help in preparing
Florida Agricultural Experiment Stations
have found that liming of acid soils containing large accumula-
tions of copper reduced copper toxicity symptoms.
The fact that many citrus groves already contain sufficient
amounts of copper to meet the tree needs and that many old
groves and vegetable fields contain excess amounts of copper
indicates a need for a convenient rapid method of determining
the copper content of the soil. Such a rapid test, accurate to
within 50 pounds copper per acre, is described here. The test
is based on the brown precipitate formed when sodium diethyl-
dithiocarbamate is added to a copper solution. This reagent
is made specific for copper according to the method of Cheng
and Bray (3) by adding disodium ethylenediamine tetraacetate
(EDTA) to the carbamate reagent to eliminate interference
of iron and other heavy metals. The technique of running the
test is similar to that described by Cheng and Bray (2) for
magnesium in soil. The copper is leached from a small cone
of soil on filter paper by the addition of several drops of 1 N HCI.
The filter paper is then turned over and the color developed by
the addition of a strongly buffered solution of the carbamate
and EDTA reagent. The intensity of brown color is compared
with a standard color chart.
REAGENTS AND MATERIALS
1. Leaching Solution.-Approximately 1 N HC1. Dilute 8 ml.
concentrated HCI to 100 ml. Add 5 drops of a wetting agent
such as Ultra Wet 60 L. The wetting agent is not necessary on
most soils but does give better leaching action on soils which
are hard to wet.
2. Carbamate Reagent.-Dissolve 16 grams of disodium ethyl-
enediamine tetraacetate (diNaEDTA)2 and 0.250 grams sodium
diethyldithiocarbamate in 80 ml. of an ammonium citrate solu-
tion containing 22 grams ammonium citrate and 130 ml. con-
centrated NH4OH per liter. Dilute to 100 ml. This solution
is stable for several months if kept in well stoppered dark glass
bottles or if kept in the dark in clear glass bottles. The usual
interfering elements-iron, cobalt, chromium and bismuth-do
not give interfering colors with this reagent in the presence of
the above concentrations of diNaEDTA and NH40H.
STrade names for diNaEDTA are SEQUESTRENE NA, which is manu-
factured by Alrose Chemical Co., Providence, R. I., and Disodium Versenate
which is manufactured by Bersworth Chemical Co., Framingham, Mass.
A Rapid Test for Excesses of Copper in Sandy Soils 7
3. Filter Paper.-A smooth surface filter paper is required.3
Cut into strips 3" x 4".
4. Soil Sample.-The use of an adequate soil sample is just
as important for this test as for any other soil test. Volk and
Peech (12) discussed factors affecting the soil sampling pro-
cedure under citrus grove conditions. Wander (13) emphasized
the importance of using an adequate soil sample for testing
purposes and outlined the procedure for obtaining one. Samples
should be taken at the leaf drip or periphery of the tree to a
depth of 6 inches. At least 16 single samples should be taken
from the desired area and mixed as a composite to represent
the soil in this area. Usually one composite sample for an acre
or two should be sufficient. After the composite sample is air-
dried and thoroughly mixed the test can be carried out as out-
Fig. 1.-A small amount of soil-approximately 2 grams-is placed on
a strip of filter paper in a cone-shaped mound. A small depression is made
in the top of the soil cone to allow the solution to penetrate the soil.
RUNNING THE TEST
Place about 2 grams of soil (approximately 1/2 teaspoonful)
on a strip of filter paper in a cone-shaped mound (Fig. 1). After
SSouthern Scientific Company's filter paper No. 13061, formerly No. 7677,
was found to be suitable.
Florida Agricultural Experiment Stations
Fig. 2.-The leaching solution is added drop by drop onto the soil cone
until it spreads out on the filter paper about Vs inch beyond the edge of the
soil cone (this requires approximately 20 drops of solution). This extracts
the copper from the soil and carries it into the surrounding area of the
paper. Do not allow the solution to run down the outside of the soil cone.
Fig. 3.-The filter paper is folded over the soil and the carbamate solu-
tion is applied to the moist area of the paper by slowly moving the dropper
across this area. The copper content of the soil is found by comparing the
intensity of brown color formed by this reagent with a standard color
chart (Fig. 4).
A Rapid Test for Excesses of Copper in Sandy Soils 9
making a small depression in the top of the soil cone to prevent
runoff, add the leaching solution (1 N HC1) dropwise to the
soil cone in such a way that the solution will penetrate the soil
mass, flow through the soil and then spread out on the filter
paper (Fig. 2). Continue add- Lbs. Cu/A.
ing the leaching solution until
it spreads out on the filter paper
about 1/8 inch beyond the edge
300 or More
of the soil cone (approximately
20 drops of solution required).
This extracts the copper from
the soil and carries it into the
surrounding area of the paper.
Fold the paper over and apply
the carbamate solution to the
moist area of the paper by 2oo
slowly moving the dropper
across the outer edge of the
moist area (Fig. 3).
OF THE TEST
The intensity of brown color
formed in the test is propor-
tional to the copper content of
the soil. Compare the intensity
of the brown color with the
standard color chart (Fig. 4).
The color chart was standard-
ized by comparison with the 50
color developed using sandy cit-
rus grove soils of known copper
content. The various intensities
The v s i Fig. 4.-Standard color c h a r t
of brown color corresponding to showing the intensities of brown
pounds copper per acre in soils color corresponding to the various
such as those of the Lakeland, concentrations of copper in the soil.
Blanton, Ft. Meade, Eustis, Leon and Orlando series are given in
Fig. 4. This chart has not been tested for other soil types and
restandardization may be necessary before it can be applied to
heavier soils or soils with high organic matter content. For
example, 200 pounds Cu per acre in a heavy soil or one contain-
ing a high percentage of organic matter may not give the same
Florida Agricultural Experiment Stations
intensity of brown color as 200 pounds Cu per acre in soils
similar to those above, even though the color intensity would
be proportional to the copper content of the soil in each case.
A virgin soil (Lakeland fine sand) gave no perceptible brown
color in the test.
The approximate amount of copper in soils containing more
than 300 pounds Cu per acre can be determined by diluting the
soil sample with virgin soil or inert sand and carrying out the
test on the mixture. The concentration of copper found in the
mixture is then multiplied by the dilution factor to calculate
the concentration of copper in the original soil sample. For
example, if equal volumes of soil sample and virgin soil are used,
the amount of copper found in this mixture should be multiplied
by two. For most accurate determinations, soils with very high
copper concentrations should be diluted so that the copper con-
centration of the diluted mixture falls within the range of
100 300 pounds copper per acre.
USE OF THE TEST
The test can be used to determine the approximate amount
of copper which has accumulated in acid sandy soils.
If the test indicates the presence of relatively large accumula-
tions of copper in citrus groves, the soil pH should be carefully
controlled above pH 5.5. Wander (14) found that increasing
amounts of copper were retained in the surface 6 inches of soil
as the soil pH was increased from 3.7 to 6.0. Hence, in addition
to controlling availability, a pH above 5.5 will tend to reduce
leaching of copper from the organic matter zone into the lower
subsoil zones which are very low in organic matter. In the
absence of organic matter this leached copper will be highly
available and toxic if present in sufficient amounts. Thus it is
advantageous to keep the copper in the upper soil zone, which is
relatively high in organic matter, and where it is possible to
control its availability.
The minimum amount of copper necessary for optimum growth
of citrus is not definitely known. This amount will depend some-
what on the soil, but it is believed that 50 pounds copper per
acre is sufficient for citrus growing on acid soils (5). Thus, if
the test indicates the presence of approximately 50 pounds cop-
per per acre the grove does not need additional copper in the
fertilizer. If copper sprays are being used for melanose control,
no copper is needed in the fertilizer at any soil copper level.
A Rapid Test for Excesses of Copper in Sandy Soils 11
PERSONAL VARIATION IN APPLICATION OF THE TEST
To evaluate the personal variation in the application of the
proposed method, several sandy soils were analyzed for total
copper by 18 individuals at the Citrus Experiment Station.
These individuals had not previously used the test and were not
instructed in its use other than by reading the manuscript. Thus,
variations in their results should be the maximum variation
which will be encountered in the use of the test. Their results,
summarized in Table 1, are in fairly good agreement with those
obtained by standard laboratory procedures. The variation in
individual results is not wide when the significance of the various
amounts of copper is considered. Results obtained by such a
color comparison method should be more accurate and consistent
as the operator gains experience in running the test. For this
reason most reliable results will be obtained by qualified per-
sonnel who have an opportunity, through repeated use, to be-
come most familiar with the method.
TABLE 1.-SUMMARY OF SOIL ANALYSIS FOR TOTAL COPPER BY THE PRO-
POSED METHOD EXPRESSED AS THE NUMBER OF ANALYSES REPORTED AT
EACH LEVEL OF COPPER.
Sample Cu*: Copper Level, Lbs. Cu/A.
S50 75** 100 150** 200 250"* 300
1 208 1 2 12 3
2 252 8 4 6
3 50 15 2 1
4 98 2 3 13
5 177 1 4 12 1
6 387 18
Average of triplicate determinations by a nitric-perchloric acid digestion procedure.
** Thee individuals reported copper contents appeared to be between the levels desig-
na'Led on the standard color chart.
1. CHAPMAN, H. D., G. F. LIEBIG, JR., and A. P. VANSELOW. Some nu-
tritional relationships as revealed by a study of mineral deficiency
and excess symptoms of citrus. Proc. Soil Sci. Soc. Am. 4: 196-200.
2. CHENG, K. L., and R. H. BRAY. A test for magnesium in plants and
soils. Better Crops with Plant Food 36 (1) : 13. 1952.
Florida Agricultural Experiment Stations
3. CHENG, K. L., and R. H. BRAY. Two specific methods of determining
copper in soil and in plant material. Anal. Chem. 25: 655-659. 1953.
4. ERWIN, T. C. Leaching and the availability of copper as affected by
phosphorus and lime. Proc. Soil Sci. Soc. Fla. 7: 49-57. 1945.
5. REITZ, II. J., C. D. LEONARD, J. W. SITES, W. F. SPENCER, 1. STEWART,
and I. W. WANDER. Recommended fertilizers and nutritional sprays
for ,itrus. Fla. Agr. Expt. Sta. Bul. 536. 1954.
6. REUTHER, W., and P. F. SMITH. Toxic effect of copper on growth of
citrus seedlings and its possible relation to acid-soil chlorosis in
Florida citrus groves. Citrus Magazine 14 (11) : 25-27. 1952.
7. REUTHER, W., and P. F. SMITH. Iron chlorosis in Florida groves in
relation to certain soil constituents. Proc. Fla. State Hort. Soc.
65: 62-69. 1952.
8. REUTHER, W., P. F. SMITH, and A. W. SPECHT. Accumulation of the
major bases and heavy metals in Florida citrus soils in relation to
phosphate fertilization. Soil Science 72: 375-381. 1952.
9. ROGERS, L. H., O. E. GALL, L. W. GADDUM, and R. M. BARNETTE. Dis-
tribution of macro and micro elements in some soils of Pensinsular
Florida. Fla. Agr. Expt. Sta. Bul. 341: 1-31. 1939.
10. STEENBJERG, F. Copper in the soil with special reference to the white
tip disease. Tids. Planteavl 45: 259-369, 1940, or Chem. Zentr. 1:
11. STEWART, IVAN, and C. D. LEONARD. Iron chlorosis-its possible causes
and control. Citrus Magazine 14 (10) : 22-25. 1952.
12. VOLK, G. M., and M. PEECH. Factors affecting the soil sampling pro-
cedure. Proc. Soil Sci. Soc. Fla. 2: 12-20. 1940.
13. WANDER, I. W. Soil reaction or pH. Citrus Magazine 13 (12): 17.
14. WANDER, I. W. The relation of soil reaction to retention of applied
manganese, copper and zinc in Lakeland fine sand. Fla. Agr. Exp.
Sta. Ann. Rpt. 1953.
15. WESTGATE, P. J. Preliminary report on copper toxicity and iron
chlorosis in old vegetable fields. Proc. Fla. State Hort. Soc. 65: