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SOME EFFECTS OF SULFUR on CROPS AND SOILS.
INTRODUCTION.

Considerable attention has been given recently to
the use of sulfur as.a fertilizer and its effect on the soil.
In view of this fact, we conducted some experiments to find
the effect, if any, produced on the germination and early
growth of alfalfa and clover, by the addition of varying amounts
of elemental sulfur to two Michigan soils, and to make a study
of the attendant factors which might influence those results.
Before entering into a discussion of these experiments, it
seems advisable to review certain literature which may have

some bearing on the work.
REVIEW OF LITERATURE.

The effect on crops of fertilization with sulfur has
been reported by several investigators, many of whom obtained
increased yields, especially of legumes and the Cruciferae.
Boulanger (9) got increased growth of vegetables, mainly Cruci-
ferae, by the use of light applications of sulfur. Hart and
Tottingham (21) found sulfur to give the lowest yields in a
series of fertilizer tests on Miami silt loam, under greenhouse
conditions. Later (57) they found that 100 lbs. of sulfur in-
creased the yield of clover, Cruciferae and barley on a silt
loam soil. Sherbakoff (54) reported injury to clover the
following year after making heavy application of sulfur. Duly
(18) found the yield of clover was increased and the sulfur

was slightly beneficial to the growth of corn and rape. Pitz

93755

2.

(45) and Ames and Boltz (2) found that small applications
increased the yield of clover. Brown and Johnson (12 & 13)
found that in soils high in sulfur, sulfofication and yield
were not always parallel. Shedd (52) obtained increased
yields on some soils and decreases on others. Tobacco
especially responded to this treatment. He also found (51)
that in sand cultures, alfalfa responded to sulfur. Fellars
(19) obtained a greater yield of soybeans with applications
up to 200 lbs. Reimer and Tartar (46) reported a large
increase of alfalfa on various types of Oregon soils. Mc-
Taggart (37) obtained increased growth of alfalfa but no
effect on soybeans and field peas. Lipman, Prince and Blair
(31) obtained uniform germination with barley but later the
heavier applications injured the stand. Soybeans following
the barley had normal germination on the plots with light
applications, but it was depressed by the heavier ones, with
practically no germination where the sulfur was applied the
heaviest. Olson and St. John (42) obtained increased yields
of field crops with elemental sulfur. Rudolphs (47) found
soybeans to be stimulated by small amounts of sulfur. Neidig,
McDole and Magnuson (40) obtained increased yields of alfalfa
on humid soils but no effect on arid soils. McCool (33)
reported that field experiments in Michigan showed practically
no effect from the addition of sulfur. Bacon and Lint (17)
quoted data from the Coastal Plain Experimental Station at
Tifton, Ga., showing increased yields of peanuts, tomatoes
and peppers from the use of small applications of inoculated

sulfur.

Duley (18), Reimer and Tartar (46), and Neidig,

3.

MoDole and Magnuson (40) obtained their beneficial results
on soils naturally low in sulfur. Brown and Kellogg (14)
.suggested that the use of sulfur not only adds sulfur to
the soil, but makes available that already present. Shedd
(50) quoted several authorities and concluded that sulfur
should be added to the soil as a plant food. Tottingham
and Hart (57) concluded that the effect of sulfur on plant
growth is (a) by providing the nutrient 803, and (b) by
rendering P205 more available. Tottingham (56) said that
a deficiency of sulfur supply restricted plant growth of
red clover by limiting the synthesis of protein and res-
tricting the elaboration of plant growth. The injurious
results obtained by Hart and Tottingham (21) were attribut-
ed not to acidity, but to incomplete oxidation of the
sulfur to sulfites which exert a toxic effect. Boulanger
(9) concluded that the beneficial results were due to the
influence on the micro-organisms, as the results were low
on sterilized soil.

The majority of investigators found however that
the sulfur was oxidized to sulfate, largely by biological
agencies, which might explain the result noted by Boulanger.
Duley (18) found that sulfur was oxidized to sulfate both
in sand and soil cultures. Ames and Boltz (2) found in-
creased sulfate content in treated soil. Hibbard (20) found
that sulfur oxidized to sulfuric acid and neutralized alkali
soils. Brown and Kellogg (14) concluded that the oxidation
is mostly biological, tho some is due to chemical action.

MacIntyre, Gray and Shaw (37) obtained some non-biological

4.

oxidation when the sulfur was in contact with iron or iron
compounds. Demolon (17) attributed the oxidation to the
action of ammonifying organisms. Lipman, McLean and Lint

(30) proved that the biological factor was essential, and
later Lipman, Waksman and Joffe (33) isolated an organism
which produced the action. Brown and Warner (15) found that
all manures and the one soil used, contained sulfofying
organisms. Shedd (53) obtained sulfofication in all the soils
he tested. Lipman, McLean and Lint (29) obtained complete
oxidation of sulfur in a compost in 15 weeks. Their result
shows that the oxidation is dependent on soil conditions, as
there was a difference in effect in three soils. The action
is controlled by the number and activity of the bacteria, and
these are controlled by physical and chemical soil conditions.
Demolon (17) obtained the most results in a light soil high
in organic matter. Shedd (51) found that oxidation was more
rapid in a fertile soil than in a poor one. Brown and Kellogg
(14) found that organic matter aided the action, and these
authors as well as Lipman, McLean and Lint (35) found that

the moisture content was influential. Joffe (24) found in
pot tests of composts that the amount of oxidation depended
on the method of maintaining the moisture content, as the
oxidation itself and the crystallization of the CaSO4 pro-
duced, would use water, even tho there was no loss of weight
in the pot.

-J.’ L 2'. ‘
23 ' 502 ' 2320 _ 2H2So

H2304 f Oa3 (PO4)2 Z Oaso4 - 2H20 f ecaHPO4

5.

McLean (35) and hudolphs (48) found aeration to be bene-
ficial, and Rudolphs further found that light was slightly
detrimental and 30°C is the optimum temperature. Lipman
and Joffe (27) observed that the initial reaction of the
soil had little effect on the amount of oxidation or acidity
produced. Ames and Richmond (5) found that lime was
necessary for the reaction in sand, but that in acid soil,
lime depressed sulfofication. Lipman, McLean and Lint (30)
found that in a sulfur, floats, soil compost, the floats
neutralized the acid produced so it did not become toxic.
Lipman, Waksman and Joffe (32) concluded that the vitality
of the organism was decreased if too much acid was present,
and also in an alkaline medium. Brown and Johnson (12)(13)
found that lime or phOSphates on acid soil increased sulfo-
fication and (12) that the presence of sulfates had the
same effect. They state also that the sulfofying power of
soils can be determined by ten days incubation in the
laboratory. Sherbakoff (54) found that injury to clover was
less on limed soils and greater on soils low in organic
matter.

This oxidation produces an acid condition in the

soil. Duley (18) found that sulfur was oxidized to so in

4
sand and soil cultures, and that it slightly increased the
acidity. Ames and Boltz (2) found that sulfur increased
soil acidity and the amount of sulfates present. Rudolphs
(46) found that on soil fertilized for 30 years, small

amounts of sulfur did not affect the soil reaction but on

poorer (unfertilized) soil there was a change in reaction.

6.

The H ion concentration increased nearly proportionally

to the sulfur application. Lipman, McLean and Lint (29)
found that in sea sand the acidity increased up to the

10th week, then was constant. It was greater when

floats were present. In heavier soil sulfur alone pro-
duced the greater acidity. Tottingham and Hart (57)
working with composts, obtained the greatest acidity in

12 weeks. Lint (25) found all the sulfur oxidized in 8
weeks and Martin (38) assumed that total oxidation had
occurred in explaining why his results showed maximum
acidity in 10 weeks. Shedd (51) found about 60% of the
sulfur oxidized after 4 months, regardless of the amount
applied. Later (53) he reported that the same per cent of
sulfur was oxidized with different applications, tho the
weight of sulfur oxidized was greater with the larger
applications. Ames and Richmond (5) found 50% of sulfur
oxidized in an acid soil. In another case (4) they report-
ed that from 50 to 80% was oxidized in silt loam, clay loam
and muck. And recently Ames (1) reported that 50% was
oxidized with a ton application and 70% when the application
was heavier. Lipman and Joffe (27) concluded from their
investigations that the original pH of the soil had little
or no effect on the resulting pH value produced by sulfo-
fication, tho below pH 2.4 they seemed to get some variation.
They attained a pH of 2.0 in 8 weeks and in other cases
lowered the pH of the soil to 1.6 in 3% years. Joffe in
another set of experiments (22) produced a pH of 2.8 and

Lipman, Prince and Blair (31) under field conditions got a

J

7.

pH of 3.5 - 3.6 after 3 months with 4000 lbs. of sulfur.
They found that acidity did not increase materially with
heavy applications for 6-8 weeks, and attained its maximum
in the 16th week. They also ran the lime requirement on
these soils by the Veitch method but found no exact correla-
tion, the one set of results may forecast the other. Duley
(18) found that the lime requirement was directly correlated
with the amount of soluble sulfate. Contradictory results
have been obtained concerning the correlation of pH to lime
requirement in natural, untreated soils. Blair and Prince
(7) using only one soil, found rather close correlation,
while Joffe (22) with a series of different soils, and
Johnson (25) found very little correlation between these
two methods of measuring soil acidity.

Tottingham and Hart (57) concluded that the acidity
'produced by sulfofication was due to acid salts and not to
the presence of free acids, and Ames (1) found some evidence
to the same effect. Mirasol (39) quoted Veitch as having
found one or two cases where water soluble sulfuric acid was
present (in untreated soils).

Hart and Tottingham (21) did not attribute the
injruious effect of sulfur on crop yield to the resulting
acidity. Shedd (51) reported that this acidity will prevent
growth unless lime is used, and Fellers (19) explained the
crop injury in his experiments as being due to produced
‘ acidity. Reimer and Tartar (46) in recommending sulfur as
a fertilizer, advised the use of lime on acid soils. Sher-

bakoff (54) found that the injury to clover on sulfur-treated

8.

soil was less on limed soils, and greater on soils low in
organic matter.

Other investigations have shown that acidity does
affect the germination and growth of alfalfa. Joffe (23)
in a Penn loam soil obtained alfalfa germination in soils
with a pH value of 3.6 - 3.8, but found that it was greatly
reduced below pH 4.5. No germination occurred below pH 3.6
and no growth below pH 3.8. He recognized that these results
were limited due to the use of only one soil. Salter and
McIlvaine (49) found that clover germinated at Ph 2.16 but
would not grow at pH 2.96. Alfalfa did not sprout at pH
2.16 or grow below pH 4.11 with the best growth at pH 5.94.
Apparently the process of germination is not so susceptible
to injury as is the growth of plants. These authors found
that the pH values which limit germination varied with the
different plants, but a slightly acid medium was best for
germination, and bases exerted an injurious effect. Bryan
(16) found in quartz sand cultures that alfalfa and clover
will germinate at a reaction which is too acid for the
growth of seedlings. Young seedlings are more sensitive to
acidity than old plants. Red clover germinated and grew to
a small extent at pH 4.0 but alfalfa and alsike would not
grow at that reaction. Alsike did better at pH 5.0 - pH 6.0
than alfalfa or red clover.

Mirasol (39) found that aluminum salts had the same
effect on sweet clover as acidity, and concluded that aluminum
was the chief factor of acidity in the soils studied. This

was disproven by Blair and Prince (8) and Olsen (43). Olsen

9.

also found evidence to contradict the theories that only plants
which can use ammonia can grow on acid soils, and that acid
soils are low in nutrients while alkaline soils are rich in
them. He concluded that it is the H ion concentration of the
soil, as such, which exerts considerable influence on the

type of vegetation which will grow on a soil. Truog (58)
advanced four reasons why acidity affects plant growth:

a. by decreasing favorable physical conditions

b. by decreasing favorable biolOgical conditions

0. by favoring the accumulation of toxic substances

d. by decreasing available lime and other food

elements.

In addition to the increase of sulfate content,
sulfofication increases the amount of other soluble material
in the soil. Brown and Warner (6); Tottingham and Hart (57);
Shedd (53); Lipman, McLean and Lint (29) (30); and Lipman
and McLean under field conditions (28) found that more phos-
phorus was made soluble. Ames and Richmond (5) found that
in alkaline soils no P205 was made available from floats as
the soil bases reacted to neutralize the acids formed, but
. in acid soils P205 was made available. Rudolphs (47) found
that phosphorus was not made available until a pH of 3.1 -
3.8 was attained. Tottingham and Hart (57) stated that the

addition of sulfur depleted the soil of CaO and P20 Ames

5.
(l) and Ames and Boltz (3) found that potassium, calcium,
aluminum and manganese were made soluble in acid soils by
the action, direct or indirect, of sulfofication. Ammonium

sulfate was formed in some cases. Magnesium was not as

soluble as calcium. The potassium was liberated by the acid

lO.

salts formed rather than by the direct action of the acid.
Pits (45) found in agar plates that sulfur increased
ammonification and decreased nitrification. Duley (18)
found that the nitrate content varied inversely with the
amount of sulfate in the soil. Shedd (53) obtained some
evidence that nitrification was aided. Lipman, Prince and
Blair (31) found that nitrate content depended on the crop
demand and was not necessarily affected by the H ion con-
centration. McCool and Miller (34) found that the presence
of calcium sulfate increased the solubility of soils. Lipman,
Wakeman and Joffe (32) offered an explanation of the lag of
increase of soluble salts, in that insoluble sulfates were
first formed, followed by the production of soluble sulfates.
HXPTRIMWXTAL.

Experiments were carried on in the laboratory,
testing the influence of sulfur on germination and early
growth of clover and alfalfa, and the effect on the acidity
and the solubility of the soils used, to determine if there
was any correlation between these different effects. Other
experiments were made investigating the effect of leaching
on the acidity produced by the sulfur treatment. Some lime
requirement determinations were also made and compared with
the pH values of the same soils. A small number of field
experiments were conducted to find the influence of different
amounts of sulfur on the stand of clever and on soil acidity.
POT EYPTRTMHUTS. The first series of pot experiments was
run on a Coloma medium sand. It had not been limed recently,

but building material had been stored on it, so it became

11.

charged with lime. Alfalfa grew well on it in the field,
and when tested in the laboratory it showed the presence
of free carbonate. The sulfur used was first washed with
distilled water until the mixture with water showed no
depression of the freezing point.

The sulfur was mixed with the soil at the rates
of 0 lbs. 500, 1000, 1500, 2000 and 3000 lbs. per acre
respectively. The soil was then made up to what was con-
sidered to be the optimum moisture content, or 10%, and
stored in the dark, the moisture content being kept as
uniform as possible by frequent weighing and the addition
of water. Duplicate pots were made from each treatment at
the following intervals: immediately, 10 days, 20 days,
30 days and 60 days after mixing. The entire samples were
thoroughly mixed and aerated each time the pots were filled.
In each pot were planted 50 red clover and 50 alfalfa seeds
of high germination, and the seedlings were counted and re-
moved each second day. The number of seedlings appearing
above the surface was considered as representing the germin-
ation in every case except in the pots of 3000 lbs. sulfur
after 60 days incubation. In this case, germination occurred
but no growth took place, so the seeds were found and taken
out of the soil, and the per cent of germination determined.
At the end of ten days, germination was considered to be
complete and the soils were air-dried and stored for further
determinations. Hence the results obtained in these later
determinations were really those for 10, 20, 30, 40 and 70

days after treatment.

12.

The freezing point depression was used as a
measure of the total soluble salts present in the soil
samples. This is based on the fact that the magnitude of
the difference between the freezing point of a solution
and of pure water is dependent on and is a measure of the
quantity of substance dissolved. The freezing point de-
pression was found by the method developed by Bouyoucos
and McCool (10)(ll). The solution to be tested is put into
a freezing tube, the Beckman thermometer inserted so the
bulb is covered, and the tube is put into a freezing bath,

a mixture of ice, water and salt with a temperature of about
-3°C. When the thermometer shows that the solution is super-
cooled about l°C. the solution is shaken or stirred to cause
it to freeze, and when this occurs the mercury in the ther-
mometer starts to rise. The tube is then removed from the
freezing bath and placed in an air-bath immersed in the
freezing bath. When the mercury column stops rising and the
thermometer reading becomes constant, it is taken to be the
freezing point of the mixture. In this case 30% water was
added to the air-dry sand and the mixture was frozen. This
was above the saturation point of the soil, but Parker (44)
has shown that the presence of finely divided solids in a
concentrated solution will affect the freezing point depression,
and this amount of water will eliminate that cause of error.
The data given is the actual freezing point depression in
degrees Centigrade rather than parts per million of solute,
as there is no proof that the factor obtained by Bouyoucos

would be correct with the treatment given, and the depressions

15.

very directly as the amount of solute present.

The acidity was found in terms of pH, that is,
the logarithm of the reciprocal of the H ion concentration.
This was determined electrometrically on the Wendt's Electro-
Titration apparatus, following the method described by Spurway
(55). This is a process of measuring the difference in
potential between a calomel half cell of known potential and
a half cell produced by dipping a hydrogen electrode into a
solution containing hydrogen ions. From this potential
difference as shown by a voltmeter may be calculated the
strength of the solution of H ions, or from a table, the
voltmeter reading may be interpolated into pH reading.

In making these determinations 10 grams of air-
dry soil and 50 cc of freshly boiled, distilled water were
placed in an 8 oz. shaker bottle and shaken fro two hours,
after which the mixture stood for 24 hours before making
the determination. The mixture was put in a funnel shaped
dish and the hydrogen electrode dipped into it, always at the
same depth. A glass stirrer, running from an electric motor,
kept the mixture agitated. Free hydrogen was kept bubbling
over the electrode at the rate of two bubbles a second. At
five minute intervals the arm of the calomel electrode was
introduced into the suspension, always at the same depth,
and the resistance was adjusted until the galvanometer showed
no deflection. The voltmeter was then read, and the pH
obtained from a table. This was continued until there was no
change in two readings of the instrument. Before and after

each reading the arm of the calomel electrode was rinsed out

with N K01 solution, and after removing a sample from the

l4.
apparatus, the container, stirrer and hydrOgen electrode
were rinsed with distilled water.

A second series of pets was run on an acid Miami
silt loam. In this series, the two smallest applications
of sulfur were omitted, so the set as run consisted of the
soil plus sulfur at the rate of 0 lbs., 1500, 2000 and 3000
lbs. per acre. The moisture content of the soil was main-
tained as nearly as possible at 16% by the methods used in
the first series. Alfalfa and clover were potted in
duplicate at ten day intervals as before, but the 60 day
planting was omitted. The freezing point depression and pH
of these samples were found as with the sand, except that
when freezing this soil, 35% of water was used to super-
saturate it.

RESULTS. As these pots were run in duplicate, the results
given represent the average of the duplicates in each case.
The figures on germination and growth are per cents of the
total number of seeds planted in each treated soil. Figures
are shown of both clover and alfalfa, except in the case of
500 lbs. sulfur potted immediately, in which case mice

destroyed the seedlings.

15.

Table l. Germination and Growth in Medium Sand.

0 days 10 days 20 days 30 days 60 days

0 A c A 0 A 0 A c A
0# s 94 62 84 51 89 59 91 68 88 65
500# s - ------ 89 55 82 56 84 64 91 62
1000# s 89 62 95 58 86 55 ‘88 65 90 62
1500# s 90 67 91 51 89 64 89 59 78 42
(2000# 3 89 55 97 54 90 59 86 57 48 51
5000# s 88 57 90 6O 94 49 (5 '7 ) (52 74)
Growth Germination
(61 33) only, one pot

germination

Table 2. pH of Sand.

0 days 10 days 20 days 30 days 60 days
0# S 7.95 8.2 8.15 8.2 8.05
500# S 7.75 7.5 7.6 7.5 7.5
1000# S 7.65 7.55 6.75 6.7 6.5
1500# s 7.7 7.2 5.6 5.0 4.5
20005 S 7.65 7.2 4.5 4.4 5.9
5000# S 7.6 6.7 4.4 4.1 5.65

Table 3. Freezing Point Depression of.Medium Sand.

0 days 10 days 20 days 30 days 60 days
0# S .007 .016 .017 .015 .017
500# s .011 .028 .042 .045 .042
1000# S .054 .057 .045 .045 .047
1500# s .041 .045 .047 .051 .070
2000# S .041 .045 .058 .060 .080
5000# S .045 .051 .060 .075 .112

16.

Table 4. Germination and Growth on Miami Silt Loam.
0 days 10 days 20 days 30 days
0 A 0 A 0 A 0 A
0# S 65 59 86 72 89 64 80 69
1500# S 89 62 90 64 95 60 75 65
2000# S 92 68 85 59 91 61 24 10
5000# s 86 64 74 54 70 52 2 0
Table 5.- pH of Miami Silt.

0 days 10 days 20 days 30 days

0# S 4.9 5.05 4.97 5.05
1500# S 4.85 4.55 5.95 5.62
2000# s 4.75 4.1 5.75 5.4
5000# s 4.75 5.5 5.4 5.16

Table 6. Freezing Point Depressions of Silt Loam.
0 days 10 days 20 days 30 days

0# s g 0.011 0.019 0.017 0.021

1500# S 0.0215 0.042 0.0495 0.054

2000# S 0.025 0.051 0.076 0.085

50005 3 0.024 0.059 0.1045 0.1165

Discussion. From the above results it can be seen that in
the medium sand cultures, there was little apparent effect
of the sulfur on the germination and growth above ground,
except with the two heaviest applications after 30 and 60
days, the to some extent the 10 and 20 day samples showed a

slight increase over the checks of these periods. In the

17.

cases where heavier applications stood moist for some
weeks, however, the growth as indicated by the appearance
above ground, was much decreased. There was practically
no difference in the effect produced on clover and on
alfalfa, except that in the 3000# - 60 day pots, where
germination alone was counted, the alfalfa gave higher
results than in any other case, while the clover showed

a decrease. This bears out the statements already quoted,
that alfalfa and clover will germinate at a lower pH than
they will grow. The seedlings are evidently more sensitive
to acidity than are the seeds.

The acidity of the soils, and the amount of
soluble material increased with the amount of sulfur applied
and the length of time it was allowed to stand. The pH at
which growth was inhibited was about the same both the 30
and the 60 day series, and this is also true of the freezing
point depression. Fairly good growth was obtained at pH
4.3, but practically none at pH 4.1. There appears to be a
close correlation between the pH and the amount of Soluble
material present. This is noticeable in the 500 lb. treat-
ment in all periods, in the 1500 and 2000 lb. applications
after 0 days and 10 days, and in the 2000 application after
20 and 30 days. The increased soluble material in these
soils must be due to some action on the sulfur or on the
soil, and not the mere presence of the sulfur, as, before
applying, it was washed until it gave no freezing point
depression.

The results in the silt loam are very similar,

18.

but the correlation between the pH and freezing point
depression is not so marked. Also the soils became

more acid, and growth was obtained at much greater acidity
than in the sand. A pH value of 3.5 appears to have
decreased the growth slightly, but no great damage was
done until the acidity of the soil was changed to pH 3.4
or less. The growth in the 1500 and 2000 lb. pots after
20 days was as great as in any of the pots in the series,
even tho in both cases the pH was below 4.0.

From the fact that growth practically ceased in
the sand at pH 4.1 while in the silt loam the plants grew
well at pH 3.5, it is apparent that the acidity at which
a plant will grow is a pr0perty of the soil and not entirely
of the plant itself, and will vary with each soil used.

And it is evident also that this is due to some effect on
the growth of the seedling, and not on germination. In the
heavier soil, the plants are able to withstand a much
greater acidity than in the lighter one. It can be seen
from these results and from those of other experiments
quoted that the pH produced in a soil, and its effect on
plant growth, are controlled by soil conditions and will
vary in different soils, thus explaining the apparently
contradictory results of some authorities quoted.

In the sand cultures it will be observed there was
less growth with the 3000 lb. application after 30 days
than with the 2000 lb. after 60 days, altho in the latter
case the pH was less. In the same pots, the one with the

greater amount of soluble salts gave the better growth.

This is also apparent in similar pots in the silt loam

19.

series, which would seem to indicate that the death point
was not due to too great a concentration of the soil
solution.

Altho Joffe (18) when composting sulfur, found
that the amount of moisture used by the reaction and
taken up by the crystallizing CaSO4 was great enough to
influence the bacterial action, that would not be a factor
in this case, as the oxidation of the maximum amount of
sulfur applied would decrease the moisture content less
than .55.

In the untreated pots, the solubility of the
soil was increased as it stood with optimum moisture con-
tent, but the maximum was soon reached.

The pH values increased slightly when the soils
stood moistened after being air-dried. This was found
also by Spurway (55) but is contradictory to the results
of Noyes and Yoder (40) who found that acid soil, either
bare or cropped, increased in acidity when allowed to
stand with its water holding capacity half satisfied.

8. Leaching. In the leaching experiments, samples weighing
230 grams were taken of one of the treated sand cultures
and of the untreated sand. These samples were placed in
glass cylinders, making soil columns 8.5 cm. and 8.0 cm.
high respectively. Each column was leached by percolation
with 5 liters of water. Samples of the leachings were
taken after the first 250 cc. had passed through, and the
last 250 cc. of percolate were also collected. These

leachings were analysed for Ca and SO4 and the pH was taken.

20.

The pH of soil samples, taken after 4% liters had passed
through, were also found, for comparison with the unleached
soils.

Percolation was faster in the treated soil,

although this column was slightly higher.

Table 7. Results of Leaching in Treated and Untreated Soils.

BaSO4 CaO pH

in 50 cc in 50 cc
Treated unleached soil 5.5
" leached soil 5.3
First leachings 0.0320 0.0085 5.6
Last leachings trace trace 4.4
Untreated unleached soil 7.5
" leached soil 6.9
First leachings 0.0004 0.0010 7.5
Last " ------ trace 5.6

Discussion. These figures show that although the
sulfate was practically all removed by leaching, the
acidity produced by sulfofication coult not be leached
out, but, on the contrary, leaching made the soil slightly
more acid. Apparently the sulfuric acid reacted with the
soil bases as fast as it was formed, and the increased
soil acidity was due to insoluble acids or acid salts.
The alkaline soil was made much more acid by leaching,
and the last leachings from this soil were strongly acid.
Practically all the soluble calcium and sulfate
sulfur were washed from the soil. The untreated soil

contained practically no sulfates. Although the untreated

soil was alkaline and showed the presence of excess

21.

carbonate when treated with acid, the first leachings
from the treated soil contained more calcium than those
from the untreated. This shows that the treatment
makes the calcium more soluble.

From the fact that water percolated faster
through the treated soil, it would seem that the treat-
ment flocculated the colloids present.

C. Lime Requirement. Following a method outlined by
Spurway (55), the lime requirement produced by the
sulfur treatment was found in the following samples:
Sand plus 2000 lbs. sulfur after 60 days
" " 3000 lbs. " " 30 days
Silt loam plus 2000 lbs. sulfur after 30 days

" " " 2000 " " " " "

Ten grams of soil were placed in each of several shaker
bottles. Normal tenth equivalents of Ca(OH)2 were

added in steps from 1 cc to 10 co and sufficient neutral
water was added to raise the volume to 50 cc. The bottles
were then shaken for two hours and allowed to stand for

24 hours, when the pH of the contents was determined
electrometrically. By plotting curves of these results

it was possible to find the Ca(OH)z required to neutralize
the acidity produced by the sulfur, and bring the soil back
to its original reaction. From these results were calculated
the amount of 08003 required per acre to neutralize the
effect of the treatment, also the weight per acre and per

cent of sulfur oxidized.

22.

Table 8. Lime Reouirement and Amount of Sulfur Oxidized.
Lime Req. Lbs.S per A % S

oxidized oxidized
Sand - 2000# S-60 days 4100# Ca003 1512 65.6%
Sand - 5000# s-50 days 4450# 1424 47.47%
Silt loam - 2000# S-3O days 5570# 1242 62.1%
Silt loam - 5000# S-3O days 457o#' 1462 48.7%

DiscusSion. Since these pots were kept in the laboratory,
away from undesired influences, the acidity and change in pH
produced was due entirely to the treatment. Thus by titrating
this acidity it should be possible to determine the amount of
acid produced, and from this, the amount of sulfur oxidized.
In the sand however, the soil originally contained carbonates
which were broken down and the 002 lost when the pH fell
below 7. In this case, titrating with 0a(OH)2 would not
give the same reaction in the soil after the neutral point
was reached, so this probably was not an accurate measure of
the amount of acid which changed the soil from its original
pH of 8.1 to the pH value at the end of the period. However
the results obtained are quoted for comparison. In the silt
loam, where the initial reaction was acid, this objection
would not hold, and the lime requirement produced by the
treatment, and the amount of sulfur oxidized can be measured.
From the curve of the titration, it will be seen
that the heavier application of sulfur after 30 days incub-
ation, caused a greater buffering of the soil and required
more lime to neutralize it than did the lighter application

after 60 days, though the latter gave a slightly lower pH

value.

23.

The lime requirement in the sand is low, consider-
ing the final acidity of the soil, but this soil is slightly
buffered, so a little acid or base will readily change the
reaction.

In both cases it appears that a greater percent of
sulfur was oxidized with the smaller application, even though
the actual amount was less. This is also shown by the tables
of pH values and freezing point depressions already given, as
there, with the lighter applications, the pH and soluble salt
content became constant during the last two or three periods,
indicating that all the sulfur had been oxidized. Approximately
the same per cent of sulfur was oxidized with the same applic-
ation, in the two soils. '

In one soil, the pH might show a correlation with
the lime requirement but in two different soils there is no
correlation.

D. Plot Experiments. The field in which the plot work was
conducted was largely Plainfield loamy sand with a ridge of
Coloma just bordering it. Right plots, 12 by 30 feet, were
laid out in two sections, plots 1-4 being on the Plainfield,
while plots 5-8 were along the border of the Coloma. Plots
1 and 8 were untreated and the others were treated on May 21,
1923, with sulfur at the rates of 200, 500, 1000, 1500, 2000
and 3000 lbs. respectively. All were planted with mammoth
clover on May 22. Samples of soil were taken from these plots
on June 4, June 14, June 25 and Sept. 25, and the growth was
noted on these days and on Aug. 31. Unoxidized sulfur was

observed in all the treated plots at each time they were

sampled. The clover catch was poor and the vegetation pro-

24.

duoed was mainly ouack grass and other weeds. However some
data was taken.

Plots 5 and 6 are omitted from the results shown,
as they quickly became covered with wind blown sand from

adjacent fields.

Table 9. pH of Samples from Treated Plots.
June 4 June 14 June 25 Sept. 25

1. 0# S 6.2 5.87 6.1 5.2
2. 200# S 6.1 5.7 5.55 ' 4.25
5. 500% S 5.8 4.9 4.1 5.55
4. 1000# S 5.7 4.25 4.17 5.75
7. 5000# S 5.55 5.75 4.9 5.1
8. 0#:3 5.8 5.8 5.95 5.45

Notes on Stand.
June 4. Fair on plots 1-2-3-8
Poor on plot 4
Hone on plots 5-6-7
June 14. Stand fair on all plots.
June 25. Stand fair on plots 1-2-3-8
Poor on plot 4
Practically none on plots 5-6-7
Aug. 31. Growth poor on all plots. In a rough
way the stand varied inversely with the amount of sulfur
applied. Quack grass and weeds dominant, but the grass was
thin on the heavily treated plots.
Sept. 25. Same as above. Soil samples taken con-
tained unoxidized sulfur in plots 3-4-6-7, especially the
last two. Plots 1 to 4 showed very plainly the decrease in

clover due to the addition of sulfur. Plots 5 and 6 were

covered 1 to 3 inches deep with wind-blown sand from an

25.

adjacent field. Plot 7 had a few clover plants. Plot 8
had a fair stand.

Discussion. The soil in these plots before treatment

was fairly acid, so the stand, even on the check plots,
was poor. Also, the plots received no care from June 25
to Sept. 25, and the weeds started first and crowded out
the clover. So the only good results obtained are of the
acidity produced. .

The figures Show that on a light, acid soil,
the application of 3000 lbs. of sulfur produced an acidity
of pH 3.1 in feur months. The acidity produced in the
other plots was roughly in the order of the amount of
sulfur applied, and varied with the length of time after
application that the sample was taken.

There was some growth even on the most acid
soil, showing that after once getting a start, the plants
will stand a great H ion concentration. At the time of
germination, the soil was not so acid, but on June 14 the
plants were only one or two inches high, and plot 7 had
a pH value of 3.75. This is a greater acidity than the
crops on the sand in the pot tests were able to withstand.

After 34 days there was little difference in
the pH value of the plots receiving 500 lbs. and 1000 lbs.
of sulfur, and after 4 months the 500 lb. application gave

a slightly greater acidity.
Summary.

Pot cultures of clover and alfalfa were made on

sulfur treated soils after different intervals, and other

26.

determinations were then made on these soils.

Sulfur in light applications or in the early
stages of incubation had no effect on growth, but heavy
applications decreased it.

The acidity and soluble salt content of the
soils increased with the amount of sulfur applied and
with the length of the incubation period.

There is some correlation between the pH and
total soluble salt content of the soils.

In the heavier soils, the plants were able to
withstand a much greater acidity than in the lighter ones.

Decrease in growth was not due to too great a
concentration of the soil solution.

Germination will occur at a lower pH than growth.
Germination occurred in sand at pH 3.65 and some growth
at pH 3.9, while in the silt loam some growth occurred at
pH 3.4 and a normal stand was found at pH 3.75.

The pH produced by this treatment, and the
acidity which a plant can stand appear to be controlled
by soil conditions and will vary in different soils.

The pH value of untreated soils increased slightly
when they stood moistened after being air-dried.

The acidity produced by sulfofication cannot be
leached out. Apparently it is not due to soluble sulfuric
acid nor acid sulfates.

The treatment increased the solubility of calcium.

The heavier applications with short incubation

periods produced a greater buffering effect in the soil

27.

than lighter applications with longer incubation
periods.

In one soil there may be some correlation
between pH and lime requirement but this is not true with
figures obtained from different soils.

In both soils used, the lighter applications
showed a greater per cent of sulfur oxidized, and the
per cent was about the same with eoual applications in
the different soils.

In the plot experiments, the stand was poor on
all plots, but some growth of mammoth clover was observed
on a soil with a pH of 3.1, and a fair growth occurred on

soils with pH 3.55 - 3.75.

The author wishes to acknowledge his gratitude
to Dr..M. M. M00001 for his many helpful suggestions,
and to Professor 0. H. Spurway for his assistance in

interpreting the chemical determinations.

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