u-i
I-
C,)
January
1979
Procedures Used by the
Auburn University
Soil Testing Laboratory

PROCEDURES USED BY THE AUBURN UNIVERSITY
SOIL TESTING LABORATORY
January, 1979
TABLE OF CONTENTS
P age
I. Introduction...1
II. Soil Sample Preparation..... 1
III. Sample Extraction ..... ... ...... 2
IV. Soil pH and, Lime Requirement Determinations .. ...... 2
V. Routine Elemental Analyses.............. ...- 3
A. Phosphorus......................3
B.- Calcium................ ........ 3
C. Potassium and Magnesium................3
VI. Special Analyses..... .......................
A.
B.
C.
D.
E.
Zinc...........................
M4anganese.......................5
Soil Organic Matter...............5
Soluble Salts....................6
Determination of Nitrate in Soils.............6
VII, Preparation of Reagents...... .................. 8
A.
B.
C.
D.
Adams-Evans Buffer for Lime Requirement........8
Extracting Solutions.................8
Phosphorus Reagents
Calcium Reagents .... 9
TABLE OF CONTENTS (Continued)
VIII. Preparation of Stock Solutions and Standards
A. Phosphorus Standard.
B.. Potassium Standard.
C. Magnesium Standard.
D. Calcium Standard..
IX. Computer Data............
X. PlantAnalysis. .
. .. ..... 9
...............................11
LIST OF TABLES
Table Page
1. The amount of agricultural lime. needed to raise
the pH of acid soils to 6.5 based on the soil pH
and the "Adams-Evans" buffer pH...........4
2. Interpretation of soluble salt measurement. ..... 7
3. Preparation of P, K, Mg, and Ca standards from
stock solutions.....................10
0 .00.0 9
.9
. 9
. 9
. 9
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PROCEDURES USED BY THE AUBURN UNIVERSITY
SOIL TESTING LABORATORY
N. V. Hue and C. E. Evans
1
I. Introduction
The soil testing program of Auburn University is a joint program of the
Agricultural Experiment Station and the Cooperative Extension Service.
The Agricultural Experiment Station conducts soil test calibration research,
operates the soil testing laboratory, and makes recommendations. The
Cooperative Extension Service has primary responsibility for education on
soil testing and distribution of supplies.
Soil samples are routinely tested for pH, lime requirement, and available
P,K, Mg, and Ca. Available calcium is only reported on samples where peanuts,
tomatoes, peppers, or peaches are to be grown. When requested and a need
is indicated, soil organic matter, soluble salts and the micronutrients such
as Zn,Mn,, andi Fe may be determined for additional charges. Fertilizer re-
commendations are made from the soil test results. In addition to routine
soil tests, a pecan leaf analysis service is offered.
II. Soil Sample Preparation
1. Open samples daily. Check names, addresses, numbering of samples, in-
formation sheets, and payments ($2.00 per sample, $1.00 extra when or-
ganic matter determination is requested).
2. Place samples on shelves and number consecutively beginning with No. 1
the first of July.
3. Classify each soil sample (soil group 1 to 5) by computer based on cat-
ion exchange capacity and geographic location:
Soil Group 1 Sandy soils with CEC<4.3'meq. per 100 g. (Norfolk, Kal-
mia, Ruston, Orangeburg, Dothan, etc.)
Soil Group 2 Loams and light clays with CEC 4.3-8.4 meq. per 100 g.
(Greenville, Lucedale, Savannah, Cecil, Appling, Col-
bert, Hartsells, etc.)
1
Research Associate and Associate Professor, resectively.
-2-
Soil Group 3 Blackbelt soils with CEC >8.4 meq./100g. (Houston, Sumter,
Vaiden, etc.)
Soil Group 5 Limestone Valleys soils with CEC 78.4 meq./100 g. (De-
catur, Dewey, etc.)
4. Place samples in lab. trays. in sequence beginning on the left front row of
the tray. Fill in rows of 6 deep and 6 rows to a tray and place in heated
drying cabinet at 55oC (130
0
F) for at least 24 hours or until samples are
dry.
5. After samples are dry, screen through a 10-mesh standard sieve or grind in
a mechanical grinder. After thorough mixing, samples are ready for analy-
sis.
III. Sample Extraction
1. Weigh a 5 g, sample and transfer to a 50 ml Erlenmeyer flask (12, 50
ml Erlenmeyer flasks are fitted into special wooden racks which are
numbered at each end).
2. Deliver a 20 ml volume of extracting solution simultaneously to each
of the 12 flasks with an automatic pipette rack.
3. Place a set of racks (a maximum of 6) on a mechanical shaker set at
180 oscillations per minute with a 1 inch stroke. Shake for 5 min.
4. Filter the samples immediately through a 9.0 cm Whatman No. 1 filter
paper into 1 oz. plastic cups. The cups are fitted into racks con-
gruent to the extraction racks.
5. Pour the filtered sample extracts into vials fitted in racks. Samples
are now ready for analytical determinations.
NOTE: All soils are extracted using the double-acid extracting solu-
tion..(Mehlich, 1953). However, those soils classified in soil
group 3 must be re-extracted separately with the Mississippi
extracting solution (Lancaster, 1970).
Soil-test P, K, Mg, and especially Ca usually read higher and
the lab results will have to be corrected.
IV. Soil pH and Lime Requirement Determinations (Adams and Evans, 1962)
1. Transfer one scoop of soil (20 ml volume) to a 3 oz. waxed paper cup
and add 20 ml of distilled water by means of an automatic pipette rack.
2. Place a tray of 48 samples on a stirring machine equipped to stir all
simultaneously. Stirrers should be rinsed between stirring each tray.
After stirring for 30 sec., let samples stand for at least 30 min.
3. Stir each sample immediately before making pH determination. The pH
meter should be calibrated before use as well as regularly throughout
the day's run. Buffer solutions with pH of 4.00 and 7.00 should be
used.
-3-
4. After recording water pH, add 20 ml of Adams-Evans buffer solution with
a similar machine as was used for adding water.
5. Stir for 4 min. on the same mechanical stirrer.
6. Set standard pH meter for expanded scale using buffer 7.0 and a blank
of Adams-Evans buffer solution (1:1 buffer-water solution with pH 
8.0).
7. Read buffer pH while stirring. (Changes in digital read-out during this
reading indicates incomplete mixing 
of soil-buffer).
8. Take water pH readings with one decimal, buffer pH 2 decimals.
V. Routine Elemental Analysis
A. Phosphorus (Watanabe and Olsen, 1965)
1. Add one part (.35 ml) of the soil extract to 24 parts (8.40 ml)
of phosporus Reagent C (color developer) using a diluter-dispens-
er set for 1:24. This solution is transferred into glass vials
for P determination.
2. Aliquot duplicate set of standards from 0 to 16.35 ppm P (table 3).
3. Allow 30 min. for color to develop.
a. Allow 30 min. period of warmup after turning instrument on.
b. Read absorbance on Bausch and Lomb Spectronic 100 at 740 nm
wavelength.
B. Calcium and Magnesium
1. Using a similar diluter-dispenser, take a 1.5 ml aliquot of ex-
tract and dilute with 6.0 ml of .5%Lanthanum solution (100 ml of
5% Lanthanum solution diluted to 1 liter with acid extracting sol-
ution).
2. Dilute standards of 0 to 60 ppm Ca and 0 to 6 ppm Mg using the
same procedure as extracts (table 3).
3. Read concentration on a Perkin-Elmer model 373 or 460 Atomic Ab-
sorption Spectrophotometer with air/acetylene flame adjusted for
maximum sensitivity.
C. Potassium
Potassium is read on undiluted extract in concentration on the same
Atomic Absorption Spectrophotometer.
VI. Special Analyses
A. Zinc
Pre-rinse glassware with 1 N HCL. Use standard extracting pro-
Lime Requirement for 8-inch Furrow Slice to pH 6.5 (Adams-Evans Buffer Procedure)
Hundreds of Pounds Ag. Lime (CaC)
3 
X 1 )
Tons
per Buffer 
Water pH
acre pH 5.9 5.8 5.7 
5.6 5.5 5.4 5.3 5.2 5.1 5.0 
4.9 4.8 4.7 4.6 4.5
7.85 9 10 11 11 12 13 13 14 15 
15 16 16 17 17 18
7.80 12 13 14 15 16 17 18 19 
19 20 21 22 22 23 24
7.75 15 16 18 19 20 21 22 
23 24 25 26
1.0
7.70 17 19 21 23 24 26 27 
28 29 30 31 32 33 34 36
7.65 20 23 25 27 28 30 31 33 
34 35 37 38 39 40 42
7.60 23 26 28 30 32 34 36 37 
39 40 42 43 44 46 48
7.55 26 29 32 34 36 38 40 42 44 46 47 49 50 
52 53
7.50 29 32 35 38 40 43 46 47 49 51 52 
54 56 57 59
1.5
7.45 32 36 39 42 44 47 49 52 
54 56 58 59 61 63 65
7.40 35 39 42 46 48 51 
54 56 59 61 63 65 67 69 
71
7.35 38 42 46 49 53 56 58 61 
63 66 68 70 72 75 77
2.0
7.30 41 45 49 53 57 60 63 
66 68 71 73 76 78 80 83
7.25 44 48 53 57 61 64 
67 70 73 76 78 81 84 86 
89
7.20 47 52 56 61 65 68 
72 75 78 81 84 86 89 92 
95
2.5 7.15 49 55 60 64 69 
73 76 80 83 86 89 92 95 98 
101
7.10 52 58 63 68 73 77 81 84 88 91 
94 97 100 103 107
7.05 55 61 67 72 77 81 85 
89 93 96 99 103 106 109 113
7.00 58 65 70 76 81 85 90 
94 98 101 105 108 111 115 119
Auburn University Soil Testing Laboratory, October, 1974.
4.4 Tons
19 1.0
25
1.5
31
38
2.0
44
50 2.5
56
3.0
63
69 3.5
75
4.0
81
S88
94
100
106 4.5
113
119
125
cedure. Read on AA in lb/acre available Zn. Use standards 0-10 ppm.
Zn values must be recorded by hand on each soil test report since the
computer is not programmed to report Zn.
B. Manganese Determination
Use routine extracting procedures. Read on AA and report in the
same manner as Zn. 
Use standards of 0-20 ppm.
C. Determination of Soil Organic Matter, modified Jackson's procedure
(Jackson, 1958)
1. Weigh 0.5 gram of oven-dry soil into a 250 ml flask. If soil
is sandy or low in organic matter, 
use a 1 gram sample.
2. Add exactly 10 ml of 1 N K
2
Cr20
7
.
3. Add rapidly, 10 ml of conc. H
2
S0
4
.
4. Shake for 1 minute; let stand for 30 minutes.
5. Add 100 ml distilled water. Ten ml of 85% H
3
P0
4 
may be added for
a clearer titration endpoint but this is optional. Solution may
also be filtered if necessary.
6. Add approximately 3 drops of 0.025 M Ortho-Phenanthroline ferrous
sulphate solution.
7. Titrate with 0.5 N EeSO . FeSO
4 
normality should be determined be-
fore each run since it is likely to change slightly from day to
day. Use two blanks for this.
8. Make the following calculation:
(m.e. Ox.- m.e. Red.) X 0.3
%C 
=  
Wt. of dry 
soil1
%0.M. = %C X 1.72
m.e. Ox. = 
N X ml. K
2
Cr
2
0
7
m.e. Red. = N X ml. FeSO
4
Reagents:
1. 1 2N K
2
Cr
2
0
7
: Dissolve 49.04 grams of K
2
Cr
2
0
7
, dried at 1040, in
one liter of deionized water.
2. 0.5 N FeSO
4
: Dissolve 140 grams of FeSO
4 
" 7H
2
0 in deionized water.
Add 40 ml conc. H
2
50
4 
and make to one liter.
3. Use commercial, reagent grade, 0.025 M Ortho-phenanthroline ferrous
sulphate solution ("Ferroin").
-6-
An alternative is the use of a Carbon analyzer from LECO Inc. Co.
that reads directly percent carbon from 
the sample based on
the Infrared absorption of CO
2
.
D. Soluble Salts
1. A 40 ml volume of.soil is placed into a 250 ml Erlenmeyer flask.
2. Add 
80 ml 
distilled 
H
2
0.
3. Shake in mechanical shaker for 15 minutes.
4. Allow to stand for about 20 minutes and filter using Buchner fun-
nel.
5. Read on Solu-bridge. Determine specific conductance of liquid
and refer to table 2 for interpretations.
E. Determination of Nitrate 
in Soils
1. Phenoldisulfonic Acid Procedure (Sou. Coop. Series, 1965; Bremner,
1965)
Reagents:
(a) Sodium hydroxide I N
(b) Phenoldisulfonic acid: Dissolve 25 grams of pure, white phen-
ol in 150 ml of concentrated H
2
SO
4 
in a 500-ml Erlenmeyer flask.
Then add 75 ml of fuming H
2
SO0
4 
(13% SOq), mix the solution,
and place the flask (loosely stopperedJ in boiling water for
2 hours.
(c) Ammonium hydroxide solution (NH
4
OH): Mix equal parts of rea-
gent-grade NH
4
OH with distilled water.
(d) Standard nitrate solution: Dissolve 3.608 grams of oven-dried
KNO
3 
in distilled Water and dilute to 1 liter in a volumetric
flask. This should contain 500 ppm nitrate. Prepare working
standards of 0 to 20 with proper dilution. Standard solutions
should be kept refrigerated.
Extraction of Soils:
(a) Place 2 g of soil in a 50 ml Erlenmeyer flask.
(b) Add 20 ml of distilled water.
(c) Shake for 15 min. and filter.
Procedure:
(a) Place 2 ml of the soil extract in a 50 ml pyrex beaker then add
1 drop of 1 N NaOH, and evaporate to dryness on a hot plate (110
0
C).
-7-
Table 2. Interpretation of soluble salt 
measurement **
The level (reading) of soluble salts which most plants 
tolerate
without injury is greatly influenced by the amount of available
water, temperature, uniformity of soil-fertilizer mixture, 
amount
of organic matter, soil texture, fertilizer materials used and
other factors peculiar to each operation. The following is a
general interpretation which will serve as a guide:
Reading
(mho x 10
-
5) Effect
0-25 Salinity effect negligible. Probably too low for
good growth of most crops in greenhouse culture.
26-50 May be inadequate except where fertilizer is applied
with each watering or on very light soils.
51-125 Satisfactory for well drained greenhouse soils.
Germination of sensitive crops may be restricted and
seedlings may be injured.
126-175 Yields of many crops may be restricted. Higher than
desirable for greenhouse soils.
More than Leach with enough water so that 2-4 quarts pass
175 through each square foot of bench area or one pint
of water per 6 inch pot; wait 30 to 90 minutes and
repeat. A third application may be necessary if
readings are excessively high.
** North Carolina Department of Agriculture
Soil Testing Division
Raleigh, North Carolina 27602
-8-
(b) Cool. Add 1 ml of phenoldisulfonic acid and rotate to dissolve
the residue.
(c) After 10 minutes, add 5 ml of distilled water. Let it cool down,
and add 6 ml of the ammonium hydroxide solution.
(d) Read absorbance on B & L Spectronic 100 at 420 nm wavelength after
15 min. standing.
(e) Standards of 0 to 20 ppm of N-NO
3 
should be run with the samples.
The nitrate content of the samples is determined directly from the
calibration graph. Extractions reading greater than 20 ppm should
be diluted and analyzed again with new standards.
VII. Preparation of Reagents
A. Adams-Evans Buffer for Lime Requirement (Adams and Evans, 1962)
1. Dissolve 360 g p-Nitrophenol (practical grade) in approximate-
ly 4 1. of hot, deionized H20. Use low heat to dissolve.
2. Dissolve 270 g . of boric acid in 3 1. hot, deionized H20. Use
low heat if 
necessary.
3. Dissolve 189 g of potassium hydroxide (KOH) in approximately
200 ml deionized H20.
4. Place 1,332 g of potassium chloride (KC1) in 18-1. bottle. To
this add about 6 liters distilled H20. Mix thoroughly.
5. To the KC1 solution,. add the previously mixed solutions in same
order as listed. Make to 18 liters with deionized H
2
0. Adjust
the pH to 8.00 with KOH or HC1 if necessary.
B. Extracting Solutions (Mehlich, 1953; Lancaster, 1970)
1. 0.05 N HC and 0.025 N HSO4 mixture. Pour approximately 30 1. dis-
tilled 120 into 40-1. bottle. Add 28 ml conc. H2504 and 166 ml conc.
HC1l. Make to 40 1. with distilled H
2
0. Mix thoroughly.
2. Mississippi Method (for group 3 soils). Add 900 ml glacial acetic
acid, 65 g malonic acid (Eastman practical of equivalent),
CH
2
(CO
2
H)
2
, 120 g? malic acid (Eastman practical),CH
2
CHOH(CO
2
H
2
)
2
,
and 13.8 g ammonium fluoride, NH
4
F, to 7500 ml deionized H20 and
mix well to dissolve reagents. Add 30 g aluminum chloride hexa-
hydrate, AlCl3*6H20
, 
mix well, and adjust pH to 4.0 with NH
4
OH. Di-
lute to 10 1. with deionized H20. Mix thoroughly.
C. Phosphorus Reagents (Watanabe and Olsen, 1965)
1. Reagent A. Dissolve 100 g ammonium molybdate, (NH
4
)
6
Mo
7
024"4H20,
in approximately 500 ml deionized HO in 2-liter volumetric flask.
Dissolve 2.425 g antimony potassium tartrate, K(SbO)C
4
H
4
04" H
2
0, in
-9-
molybdate solution. Add 1,400 ml cone. H2SO4, 
cool, and make to vol-
ume with distilled H20. Store in polyethylene or pyrex glass 
bot-
tle in a dark, cool compartment.
2. Reagent B. Dissolve 88.0 g reagent grade ascorbic 
acid in dis-
tilled H20 dilute to 
1 1. Store in dark 
glass in cool compartment.
3. Reagent C (Working Solution). Dilute needed 
quantity of Reagents
A and B using the following ratio: 1 ml B + 2 ml A + 97 
ml ex-
tracting solution for a total volume of 100 ml. Prepare fresh
daily allowing to stand a minimum of 2 hr and a maximum of 24
hrs.
D. Calcium Reagents
5% Lanthanum Solution. Wet 58.65 grams La
2
0
3 
with distilled H
2
0.
Add 250 ml conc. HC1 very slowly until material is dissolved. Dilute
to 1 liter with distilled H 0. Working solution - Dilute Lanthanum
solution to 0.5% as needed 100 ml of 5% La solution to 1 1. with
acid extracting solution).
VIII. Preparation of Stock Solutions and Standards
A. Phosphorus Standard (1,000 ppm P). Place 4.392 g of oven dry po-
tassium biphosphate (KH
2
PO
4
) in 1 liter volumetric flask. Dissolve
in acid extracting solution and make to volume 
with the same extract-
ing solution. Dilute according to 
data in table 3.
B. Potassium Standard (1,000 ppm K). Place 3.8132 g of 
oven-dry po-
tassium chloride (KC1) in 2-1. volumetric flask. Dissolve and make
to volume with acid extracting solution. Dilute according to data
in table 3.
C. Magnesium Standard (1,000 ppm Mg). Dissolve 1.000 g. pure magnesium
(Mg) in a minimum volume of conc. HC 1,dilute to 1 1. Dilute according
to data in table 3.
D. Calcium Standard (1,000 ppm Ca). Weigh 5.0 g calcium carbonate
(CaCO
3
) into a 2-liter volumetric flask. Dissolve in 50 ml of 3 N
HC1. Make to volume with acid extracting solution.
IX. Computer Data
For each farmer that sends in a soil sample, 
at least 3 computer files
are punched with information which will 
be used by the computer program
in reporting test results and in making fertilizer 
recommendations. The
3 files contain the following information:
Name file: This file contains the farmer's 
name, address, county code
-10-
Table 3. Preparation of P, K, Mg, and Ca standards 
from stock
solutions 1/
Volume of 1,000 ppm stock std. diluted to 1 liter
Std. Sol. with acid extracting solution (ml per 
liter)
number _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
P K Mg Cat!
0
10
15
20
25
5
10
20
30
40.
2
10
20-
40
806
8 120
16050 10
1/ Above volumes of P, K,
are also equivalent. to
Ca, and Mg stock solutions taken per liter
ppm.
2/ To convert ppm in sample extracts to lb. per acre, multiply by 8.
Calcium standards contain 100 ml 5% La per liter, making them 0.5%
La.
..
-11-
number, number of samples, number 
of copies, and farmer num-
ber.
Crop file: This file contains 
the sample name or number, crop to 
be
grown, crop code number (for 
fertilizer recommendation),
laboratory number, number of crops 
for that sample, and
farmer number.
Sample file: This file contains the 
farmer number, the laboratory num-
ber, number of crops 
for which recommendations 
are given,
soil pH, buffer pH, Ca, P, K, and 
Mg, and special comment
number which can be added if desired.
A computer program is written to convert 
the absorbance of P ready
ings and Ca reading to Ib./A.
Soil test reports are computer 
printed for each farmer on special
forms (Soil Test Form B). The report 
contains his sample designation,
pH value, P, K, Ca, and Mg values reported in percent 
sufficiency (fer-
tility index). Each value is rated excessively 
high, very high, high,
medium, low, or very low for each element. Fertilizer 
and lime recom-
mendations are made for each crop to be grown for 
that sample. On sam-
ples where special analyses such as Zn, Mn, organic 
matter, soluble
salts, etc. are made, the results 
are written on the report by hand.
X. Plant Analysis
The Soil Testing Laboratory offers a pecan 
leaf analysis service where
a routine soil test plus Ca and Zn and a pecan 
leaf analysis for N, P, K,
Mg, Ca, Zn and An are made for $10.00. Samples 
received for a pecan
leaf analysis are numbered consecutively 
beginning with number 1 for the
first sample of the calendar year (i.e., 
73-1, 73-2, 73-3, etc.). Soil
and leaf samples from the same orchard 
receive the same number.
Soil samples are also numbered and 
included in a routine "run'. Pro-
cedures for analysis are the same as 
previously described. Ca and Zn are
determined and reported in addition 
to the routine analysis.
Pecan leaf samples are tested for N, 
P, K, Ca, Mg, and Zn. Results
are reported on the enclosed sheet. 
Recommendations based on the soil
test results and leaf analysis are made 
by the Auburn University Depart-
ment of Horticulture.
Dry ash is prepared as follows:
1. Weigh 1 gram (or 0.5 gram 
if instructed) of dry plant material 
in-
to 50 ml pyrex beaker. (Plant material 
should be ground to pass
a 40-mesh, stainless steel sieve).
2. Cover with watch glass and place 
in muffle furnace. Heat to 450
0
C
and hold at that temperature until 
all carbon is burned off. The
ash should be greyish white.
-12-
3. Cool. Add 10 ml of 1 N nitric acid (HN0
3
) and evaporate to dry-
ness slowly on hot plate. Take just to dryness and do not bake.
4. Cool. Add 10 ml 1 N HCi to dissolve the residue.
5. Warm nearly to boiling then transfer to 100 ml volumetric flask.
Wash beaker 3 times with small amounts of water.
6. Bring to volume of 100 ml and filter. Do not wash filter paper
or add more water in this step.
7. Always run a blank sample.
Solutions: 1 N HCl = 166 ml conc. HCI per 2 liters
1 N HNO
3 
= 128 ml: conc. HNO
3 
per 2 liters
C. Determinations of P, K, Mg, Ca, and Zn on the ashed samples are
made according to routine procedures for each.
References
1. Adams, Fred, and C.E. Evans. 1962. 
A rapid method for measuring
lime requirement of red-yellow podzolic 
soils. Soil Sci. Soc.
Amer. Proc. 26:355-357.
2. Bremner, J.M. 1965. Inorganic forms of nitrogen. 
In C.A. Black
(ed.) Methods of soil analysis. Agronomy 9:1179-1237. 
Amer.
Soc. of Agron., Madison, Wis.
3. Jackson, M.L. 1958. Soil chemical analysis. 
Prentice-Hall, Inc.,
Englewood Cliffs, N.J. p. 219-221.
4. Lancaster, J.D. 1970. Determination of phosphorus and potassium
in soils. Miss. Agr. Exp. Sta. Mimeo.
5. Mehlich, A. 1953. Determinations of P,Ca, 
Mg K, Na, and NH
4 
by
North Carolina soil testing laboratories. 
N.C. State University.
Raleigh. Mimeo.
6. Southern Cooperative Series. 1965. Procedures 
used by state soil
testing laboratories in the southern region 
of the United States.
Bull. 102.
7. Watanabe, F.S., and S.R. Olsen. 1965. 
Test of an ascorbic acid
method for determining phosphorus in water 
and NaHCO
3 
extracts
from soil. Soil Sci. Soc. Amer. Proc. 29:677-678.


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herein is available to
all regardless 
of race,
color, or national origin.