E-134-6M-Ll80

TEXAS AGRICULTURAL EXPERIMENT STATIUN

A. B. CONNER, DIRECTOR
COLLEGE STATION, BRAZOS COUNTY, TEXAS

BULLETIN NO. 515 OCTOBER, 1935

DIVISION OF CHEMISTRY

Availability of Nitrous Nitrogen to Plants

 

AGRICULTURAL AND MECHANICAL COLLEGE 0F TEXAS
T. O. WALTON, President

Administration : Veterinary Science:

A. B. Conner, M. S., Director ‘M. Francis, D. V. M., Chief -
R. E. Karper, M. S., Vice Director H. Schmidt, D. V. M., Veterinarian
Clarice Mixson, B. A., Secretary "F. P. Mathews, D. V. M., M. S., Veterinarian
M. P. Holleman, Chief Clerk Plant Pathology and Physiology:
D. R. McDonald, Asst. Chief Clerk J. J. Taubenhaus, Ph. D., Chief
Chester Higgs, Executive Assistant W. N. Ezekiel, Ph. D., Plant Pathologist
Howard Berry, B. S., Technical Asst. L. B. Loring, M. S., Asst. Plant Pathologist

Chemistry: » G. E. Altstatt, M. S., Asst. Plant Pathologist
G- s. Fraps, Ph. D.’ Chief: State Chemist "Glenn Boyd, B. 8-, ASSt. Plant PIIlZhOlOQlSt
s. E. Asbury, M. s., chemist F“I‘J‘“P“"g lfifmfi" lfwgwélif?!
J. F. Fudge, Ph. 1).. Chemist w E5 P“ “- - -- ‘e .
E. c. Carlyle, M. s., Asst. Chemist - - aulsm- Ph- D» M'"k°'°"‘g
T. L. Ogier, B. S., Asst. Chemist fiwA-RBQPZ“;  SS" laarmhMhi/inagement‘
A. .1. Sterges, M. s., Asst. Chemist LA b M ‘S em S- i; ‘mlf, fjfagleme"
Ray Treichler, M. S., Asst. Chemist R ‘l  8g?’ ' l“ an“ anaJmU“
W. H. Walker, Asst. Chemist “a °“‘° “m” -

Jessie Whitacre, Ph. D., Chief
Mary Anna Grimes, M. S., Textiles
Sylvia Cover, Ph. D., Foods

Velma Graham, Asst. Chemist
Jeanne F. DeMottier, Asst. Chemist
W. H. Garman, M. S., Asst Chemist

A. R. Kemmerer, Ph. D., Asst. Chemist so“ Survey: .
A. W. Walde. Ph. 1).. Asst. Chemist "W- T- Cart"; B- 8-» Ch"!

F. .1. McClure, Ph. 1)., Asst. chemist E~ H- Temvhh- B- S» 5°11 Surveyor
Horticulturv J. W. Huckabee, B. S., Soil Surveyor
S H Yank“ Sc D Chief BIt. C. Mowery, B. S., Soil Surveyor

- - - - -- o any: .
Range Animal Husbandry: V. L. Cory, M. S., Acting Chief
J. M. Jones, A. M. Chief Swine Husbandry:

B. L. Warwick, Ph. D., Breeding Investiga. Fred Hale, M. S., Chief
S. P. Davis, Wool and Mohair Specialist Dairy Husbandry:
J. H. Jones, B. S., Animal Husbandman O. C. Copeland, M. S., Dairy Husbandman

Entomolo . Poultry Husbandry:
F. L. Tghyomas, Ph. 1)., Chief; State R- M» Sherwood’ M- S» Chief
Entomologist J. R. Couch, _M. S., Assoc. Poultry Hush.

H_ J_ Reinhard’ B_ s" Entomologist Paul D. Sturkie; B. S., Asst. Poultry Husb.
R. K. Fletcher, Ph. D., Entomologist Ag"cultural_Engmeering‘

W. L. oweh, J12, M.  Entomologist MEI-l giafilgritlkaflla_s-- Chi“

i; E: §§i‘$§'s,1i;.,Si</i.  s,  More. 

S. E. Jones, M. S., Entomologist Aplculture (Ran A“t°“i°_)i

F. F. Bibby, B. s., Entomologist H- B- Parks» B- S~ Chlef

"R. W. Moreland, B. S., Asst. Entomologist A" H' Alexi B- S" Quee“ Breeder
c. E. Heard, B. s., Chief Inspector F°°d Cimm‘ Servifl" ,
C. J. Burgin, B. S., Foulbrood Inspector F- D- Fllllql‘, M. S., Chief

Agronomy:
E.  Reynolds, Ph. D., Chief J
R. . Karper, M. S., Agronomist -
P. C. Mangelsdorf, Sc. D., Agronomist   glrkhigd’  slglelgegd Inalzmctor
1). '1'. Killough, M. s., Agronomist P- A- Mm” g; dr-i ° t “We” °"

J. O. Beasley, M. S., Asst. Agronomist E‘ ' ‘oore’ ee “spec or

H

S. D. Pearce, Secretary
. H. Rogers, Feed Inspector

. J. Wilson, B. S., Feed Inspector

Publications: -

A- v- Jscksos- chisr i: ‘is. ‘iiiiiizifs,vi=.llfi' FI.'Z';Z“.JJAZ"°°‘°’
SUBSTATIONS

No. 1, Beeville, Bee County: No. 9, Balmorhea, Reeves County:
R. A. Hall, B. S., Superintendent J. J. Bayles, B. S., Superintendent

No. 2, Tyler, SmithCounty: No. 10, College Station, Brazos County:
P. R. Johnson, M. S., Superintendent R. M. Sherwood, M. S., In Charge

"B. H. Hendrickson, B. S., Sci. in Soil Erosion L. J. McCall, Farm Superintendent
"R. W. Baird, M. S., Assoc. Agr. Engineer No. ll, Nacogdoches, Nacogdoches County:

No. 3, Angleton, Brazoria County: H. F. Morris, M. S. Superintendent
R. H. Stansel, M. S., Superintendent "No. 12, Chillicothe, Hardeman County:
H. M. Reed, B. S., Horticulturist "J. R. Quinby, M. S. Superintendent
No. 4, Jefferson County: "J. C. Stephens, M. A., Asst. Agronomist
R. H. Wyche, B. S., Superintendent No. 14, Sonora, Sutton-Edwards Counties:
"H. M. Beachell, B. S., Junior Agronomist W. H. Dameron, B. S., Superintendent
No. 5, Temple, Bell County: I. B. Boughton, D. V. M., Veterinarian
Henry Dunlavy, M. S., Superintendent W. T. Hardy, D. V. M., Veterinarian
C. H. Rogers, Ph. D., Plant Pathologist O. L. Carpenter, Shepherd
H. E. Rea, B. S., Agronomist "O. G. Babcock, B. S., Asst. Entomologist
"E. B. Deeter, B. S., Soil Erosion No. 15, Weslaco, Hidalgo County:
"P. L. Hflpkirlfl. B- S-, Junior Civil Engineer W. H. Friend, B. S., Superintendent
No. 6 Denton, Denton County: S. W. Clark, B. S., Entomologist
P. B. Dunkle, M. S., Superintendent W. J. Bach, M. S., Plant Pathologist
"I. M. Atkins, B. S., Junior Agronomist J. F. Wood, B. S., Horticulturist
No. 7. Spur, Dickens County: No. 16, Iowa Park, Wichita County:
R. E- Difiksflm B- S» Sllperilltfllldéflt C. H. McDowell, B. S., Superintendent
B. C. Langley, M. S., Agronomist L. E. Brooks, B. S., Horticulturist
No. 8, Lubbock, Lubbock County: No. 19, Winterhaven, Dimmit County:
D. L. Jones, Superintendent E. Mortensen, B. S., Superintendent
Frank Gaines. Irrig. and Forest Nurs. "L. R. Hawthorn, M. S., Horticulturist
Members of Teaching Staff Carrying Cooperative Projects on the Station:
G. W. Adriance, Ph. D., Horticulture W. R. Horlacher, Ph. D., Genetics
S. W. Bilsing, Ph. D., Entomology J. H. Knox, M. S., Animal Husbandry

D. Scoates, A. E., Agricultural Engineering A. L. Darnell, M. A., Dairy Husbandry
A. K. Mackey, M. S., Animal Husbandry R. O. Berry, B. S., Biology

R. G. Reeves, Ph. D., Biology R. T. Stewart, Ph.D., Agronomy

J. S. Mogford, M. S., Agronomy V. A. Little, M. S., Entomology

F. R. Brison, M. S., Horticulture

‘Dean, School of Veterinary Medicine. _ iAS 0f September 1, 1935
"In cooperation with U. S. Department of Agriculture.

IIn cooperation with Texas Extension Service. _

‘In cooperation with State Department of Agriculture.

 

CONTENTS

Page

Introduction  A 4
Experimental work  _  5
Preliminary tests with pot experimentsw- 1  .... _- 6
Availability in soils by pot experiments - 6
Availability measured by nitrogen taken up 9
Availability as measured by growth of crop _______________________________________  11,
Effect on nitrogen content of crops A 13
Nitrification in the sand used _____ Y~ 13
Nitrites in water cultures . A 15

Relative quantities of nitrate and nitrite nitrogen absorbed by corn  16

Effect of different amounts of nitrate and nitrite nitrogen upon

growth of corn   g 17
Relation of degree of acidity of the solution on the growth of
corn, cotton and oats with nitrate and nitrite nitrogen __________________ 41 19
Availability of nitrites as measured by growth in water cultures _____________ -_ 23
Summary iiii 1  A A 25

References . _- 26

The availability of nitrites was studied by means 0f pot tests
with soils and by experiments in water cultures, for the reason
that previous work has shown the possibility of the occurrence
of appreciable amounts of nitrites in some soils. Large amounts
of nitrites were injurious to plants in the pot tests. Small amounts
of nitrites seem to be taken up from the soil and" utilized as well
as the same amounts of nitrates. With somewhat larger amounts
0f nitrites, the amoount taken up was about 76% of that of nitrates,
but the plant growth was only about 25% of that produced by
nitrates. Since nitrites added to sterilized sand were partly
changed to nitrates, it was possible that there was some trans-
formation of nitrites to nitrates during the period of growth of
the plants in the soils. In water cultures the relative growth
of plants produced by nitrates and nitrites varied with the acidity
or alkalinity of the solution. Corn made the greatest growth
with the nitrates at a pH of 3.9-4.1 and the lowest growth at
6.4-7.7, while with the nitrites the growth was in the reverse order,
being lowest at pH 3.9-4.1 and highest at 6.6-7.7. Similar results
were secured with cotton and oats. If the growth of the plants
in the water cultures is taken as a measure of availability, the
availability of the nitrites at pH 6 was approximately 21 % of
that of nitrates. At a pH of 3.9-5.4 the average availability of
nitrites was 4%, while at pH 6.4-7.7 it was approximately 112%
of that of nitrates. Nitrites are more likely to occur in alkaline
soils than in acid soils. They are more readily taken up by
plants in such alkaline soils.

 

BULLETIN NO. 515 OCTOBER’ 1935

AVAILABILITY OF NITROUS NITROGEN TO PLANTS

G. S. FRAPS AND A. J. STERGES

Work previously reported by us (4) shows that nitrites may be pro-
duced in large amounts from ammonium sulphate in nitrification ex-
periments. It is possible that nitrites may be produced in the field under
some conditions when ammonium sulphate or other ammonium salts are
used as fertilizer. This renders necessary a more extensive study of the
occurrence of nitrites in field soils, the availability of nitrites, and their
possible injurious effects. Midgley (12) has shown that appreciable
quantities of nitrites may be formed in overlimed soils. Greaves et al
(7) studied the occurrence of nitrites in irrigated soils. Dratschew and
Alexandrowa (2) report that 4 to 10 parts per million of nitrites were
found in the soil solutions from certain cultivated soils. Lenglen and Mil-
hiet (10) report the presence of small amounts of nitrites in commercial
nitrate fertilizers.

Information regarding the absorption and assimilation of nitrites by
plants is very limited. A brief summary is given by Miller (13). Schultz
observed (13) that nitrites seemed to be more readily absorbed by plants
than nitrates from dilute solutions. According to Stutzer (13) a dilute
solution of nitrites seemed to be beneficial to some plants although it was
injurious to others. Strong solutions of nitrites were always more toxic
to plants than corresponding solutions of nitrates. According to Perci-
abosco and Rosso (16), plants supplied with nitrites coontain higher per-
centages of nitrogen than similar plants supplied with nitrates.

Mevius and Dikussar (11) found that in water cultures 200 parts per
million of nitrite nitrogen was not injurious to corn, although the optimum
concentration was 50 parts per million. They describe acute and chronic
nitrite poisoning. Gerlach, Schultz, and Kellner (12), found thatnitrite
nitrogen was inferior to nitrate nitrogen and in many cases when used in
large quantities was toxic, while Densch and Bobko (12) concluded that
the injury from excess of lime is partly due to the production of nitrites.
Midgley (12) did not consider the injury caused by overliming to be
due to nitrites. -

Feher and Vagi (3) found that large quantities of nitrites exert an in-
itial inhibition on plant growth. The inhibitory effect was more marked
on the roots than on the stems of the plants.

EXPERIMENTAL WORK

This study of the availability of nitrites to plants was made by two
procedures. One procedure was the usual method of ascertaining avail-
ability in pot tests, except that the soils were previously sterilized to
decrease the transformation of the nitrites to nitrates. The other pro-
cedure was by Water culture experiments, as described by Shive (17).

s BULLETIN N0. 515, TEXAS AGRICULTURAL EXPERIMENT STATION
PRELIMINARY TESTS WITH POT EXPERIMENTS

The following preliminary experiments were made on 5 kg. portions
of unsterilized soil in eight-inch galvanized iron pots. The salts were
dissolved in 100 cc water and added on the top of the soil. Five grams
of sodium nitrite added to wheat and oats before planting ‘prevented ger-
mination of all but a few seeds, but where 5 grams of sodium nitrate
was added, the germination was normal. Five grams of sodium nitrite ap-
plied to wheat and oats when about 1 inch high, a.nd also when 6 inches high,
caused the plants to turn yellow and die in about 24 hours. Sodium
nitrate added in equal amount caused no injury. Three grams of sodium
nitrite prevented germination of most of the seeds of Wheat and oats,
killed oats one inch high, and also killed plants 6 inches high. Two
grams killed oats, while 1 gram killed about one-third of the number
of young wheat plants to which it was applied. Five-tenths gram applied
to young oat plants killed about one-third of them. As little as 0.5
gram of sodium nitrite was injurious to young plants when applied to
the roots in the manner indicated, while as much as 5 grams of sodium
nitrate was not injurious. However, it is shown below that 1.5 grams
sodium nitrite was not injurious when distributed through the soil instead
of being applied in somewhat concentrated solution, as was done in the
above experiments.

AVAILABILITY IN SOILS

The availability of nitrogenous and other fertilizers to plants is usually
determined in pot experiments by comparing the growth of plants or the
quantity of the plant food taken up by the plant. The changes which
take place in the material after it is introduced into the soil are not usually
taken into consideration in such work, because these changes are a necessary
part of the conditions under which the fertilizer is to be used.

The availability of nitrous nitrogen was compared with that of nitric
nitrogen and ammonia nitrogen in 13 separate tests. Even though the
soil was sterilized, some nitrification took place, as will be shown later.
The soil was sterilized in breakers containing 200 grams by heating it to a
temperature of 150° for two hours in an electric oven. The sterilized
soil weighing 5,000 grams was then placed in sterilized galvanized iron
pots, and 1 gram each of potassium sulphate and dicalcium phosphate was
added. The nitrogenous additions were then made, followed by distilled
water equal to 50 per cent of the water-holding capacity of the soil.
The nitrogenous additions compared were nitrate of soda carrying 0.1
gram nitrogen, ammonium sulphate carrying 0.1 gram nitrogen, and
sodium nitrite carrying 0.05 gram nitrous nitrogen or the other amounts
specified. Two pots with each addition were used with most soils, although
in a few cases only one pot was used on account of the limited amount of
the soil availablef Equal weights of seed were planted in each pot of the
series. The pots were watered with distilled water three times a week.

AVAILABILITY OF NITROUS NITROGEN TO PLANTS

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8 BULLETIN NO. 515, TEXAS AGRICULTURAL EXPERIMENT STATION

Table 2. Pot test on the availability of nitrite nitrogen to corn, 1933, soil 37293

Additions of Weight Nitrogen Nitrogen Average Gain Per cen-t
_ crop, in crop, in crop, nitrogen, nitrogen, nitrogen
nltrogen gm. per cent gm. gm. gm. recovered
None 27.3 .53 .1447
None 25.0 .50 .1250 .1349
0.1 gm. nitric nitrogen 37.2» u .59 .2195
0.1 gm. nitric nitrogen 36.6 .57 .2086 .2141 .0792 79.2
0.1 gm. nitrous nitrogen 30.2 .64 .1933
0.1 gm. nitrous nitrogen 32.8 I65 .2132 .2033 .0648 60.5
0.2 gm. nitrous nitrogen 42.9 .71 .3046
0.2 gm. nitrous nitrogen 38.3 .68 .2604 .2825 .1476 65.3
0.3 gm. nitrous nitrogen 22.1 .88 .1945
0.3 gm. nitrous nitrogen 29.8 1.10 .3278 .2612 I .1269 37.4
0.3 gm. nitric nitrogen 39.0 .89 ' .3471 I I
0.3 gm. nitric nitrogen 40.7 .83 I .3378 I .3425 .2076 69.2

Some of the pots which had received nitrites were examined for nitrites at
the end of the experiment. They were present in some but not in others.

The plants growing in pots which received nitrate made a normal growth
from the seedling stage up to. the time of harvesting, while the plants
growing in pots which received nitrite had a retarded growth and some-

Table 3. Pot tests unon availability of nitrite nitrogen to corn, 1934, soil 29208

             

Addition of ~Grams Nitrogen Nitrogen Gain in Gain in Gain in Per cent
_ of in crop, .in crop, weight of nitrogen, nitrogen, nitrogen
nltrogen corn per cent gm. crop, gm. per cent gm. recovered
I I I I I I
None | 2.6 .53 .0138 |
I 2.1 .68 .0143 I
I 2 6 .57 .0148 I
Average I 2 4 .59 .0143
0.2 gm. nitrous nitrogen I 27.1 .61 .1653
I 20.8 .53 .1102
I 20.4 .57 .1163
Average I 22 8 .57 .1306 20.4 —.02 .1163 58.2
0.2 gm. nitric n-itrogen I 23.9 .56 .1338 I
I 26.5 .59 .1564
I 23.0 .58 .1334
Average I 24.5 .58 .1412 22.1 —.01 .1269 63.5
0.3 gm. nitrous nitrogen I 22.6 I .80 .1808 I
I 14.4 I 1.15 .1656
I 27.3 I .78 .2129
Average I 21.4 I .91 .1864 19.0 .32 .1721 57.4
I
0.3 gm. nitric nitrogen I 19.5 I .93 .1814 I I I I
I 28.7 I .76 I .2181 I I I I
I 31.2 I .69 I .2153 I I I I
Average I 26.5 I . 9 I 2039i I 24.1 I .20 I .1896 I 63.2
I

AVAILABILITY OF NITROUS NITROGEN TO PLANTS 9

what chlorotic condition in the seedling stage. This abnormality was
very noticeable in the corn pots which received 0.3 gram nitrite-nitrogen
and in the kafir pots which received 0.2 and 0.3 gram of nitrite-nitrogen
respectively. The corn receiving 0.3 gram and the kafir receiving 0.2 gram
nitrite-nitrogen gradually became normal in color. Some of the kafir plants
receiving 0.3 gram nitrite failed to attain a normal color.

In table 1 is given the chemical composition of the soils used, except
the builders sand, which was not analyzed.

At the end of the period of growth, the plants were cut near the surface
of the soil, dried as quickly as possible in a large drying oven, weighed,

Table 4. Pot teSts on the availability of nitrite nitrogen to kafir, 1934,‘ soil 29208

           

 

Additions of Grams Nitrogen Nitrogen Gain in Gain in Gain in Per cent
_ of in crop, in crop, weight of nitrogen, nitrogen nitrogen
nltroge“ kafir per cent gm. crop, gm. per cent gm. recovered
None 1.2 .96 .0115
1.7 .61 .0104
2 2 .58 .0128
Average 1.7 .72 .0116
0.2 gm. nitrous nitrogen 19.4 .71 .1377
I 14.5 .82 .1189 _
I‘ 12.6 1.06 .1336 I
Average II 15.5 I .86 .1301 13.8 .14 .1185 59.3
0.2 gm. nitric nitrogen I 13.0 I .92 .1196
I 20.0 .62 .1240
' 19.8 .75 .1485
Average ‘I 17.6 .76 I .1307 15.9 .04 .1191 59.6
0.3 gm. nitrous nitrogen I 1.3 I 2.81 .0365
I .4 I 3.14 .0126
II 4.6 ‘I 2.31 .1063 II ' 1
Average I 2.1 I 2.75 .0518 .4 2.03 I .0402 1.3
0.3 gm. nitric nitrogen I 27.5 I .79 .2173
I 21.7 II .93 .2018
Average I 24.6 I .86 .2096 22.9 .14 .1980 66.0

ground, and analyzed for nitrogen. Details of three of the experiments are
given in Tables 2, 3, and 4 as illustrations of the method of procedure,
and a summary is given in Table 5.

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Availability Measured by Nitrogen Taken up

The availability of the nitrogen was measured by the crop produced
and by the ‘nitrogen recovered.

The quantities of nitrogen taken up by the crop were calculated from
the percentages in the crop and from weight of the crop. The weights
of nitrogen taken from the soils which received no nitrogenous fertilizer
were substracted from the weights of nitrogen secured from the soil which
received nitrogenous additions. This gave the weight of nitrogen re-
covered by the crop. The weight recovered by the crop multiplied by 100

10 BULLETIN NO. 515, TEXAS AGRICULTURAL EXPERIMENT STATION

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AVAILABILITY OF NITROUS NITROGEN TO PLANTS 11

and divided by the quantity of nitrogen originally added to the soil
is the percentage recovered.

The resultsare summarized in Tables 5 and 6. Since the same quantities
of the various nitrogenous additions Were not applied to every soil in the
series, different averages are made for the amounts which can properly
be compared. On an average, the nitrous nitrogen is less available than
the nitric nitrogen. When the 11 comparisons secured with the addition
of 0.1 gram nitrogen are examined, on an average 50.9 per cent of the
nitrous nitrogen is recovered, compared with 69.4 per cent of the nitric
nitrogen, so that the availability of the nitrous nitrogen is little more than
70 per cent of that of nitric nitrogen.

The availability of the nitrous nitrogen was less than that of the nitric
nitrogen in 21 of the 28 comparisons. In one each of the comparisons with
soil No. 35178, soil No. 35188, and soil No. 29208, a little more of the
nitrous nitrogen than of the nitric nitrogen was apparently taken up
by the crops.

Six tests were made with 0.2 gram nitrous nitrogen. In one of the tests,
the availability of the nitrous nitrogen was one-half that of the nitric
nitrogen when 0.1 gram was applied. In the second comparison it was
zero, while with the other four it was only a little lower than that of the
nitric nitrogen. The small crop in the second comparison may have been
due to injury by the nitrous nitrogen, but it was more probably due to other
causes. With 0.3 gram nitrous nitrogen, in two of the tests the amount
of nitrogen taken up was decidedly less than that from the nitric nitrogen,
while in the other two the amount was slightly less.

Ammonium sulphate was used for comparison in three of the tests.
The nitrous nitrogen was apparently more available than the ammonia
nitrogen in two of the comparisons, and only slightly less available in
the third comparison.

While nitrous nitrogen is less available than nitric nitrogen, it was
apparently not injurious in almost all of these pot experiments. In two
tests with 0.3 and 0.2 gram in 5000 grams of soil, it was decidedly
injurious. The amount used was 20, 40, or 60 parts nitrous nitrogen per
million of the entire quantity of soil used. Apparently the method of
applying it to the dry soil before the addition of the water minimized the
injurious effect when only small amounts were added.

Availability as Measured by Growth of Crop

The availability of fertilizer materials is sometimes compared by means
of the gains in weights of the crops, instead of by the plant food taken
up, as was done above. The effect of the addition of nitrogen on the
average weight of the oven-dried crops is shown in Table 6. The gain in
weight of the crops was less with the nitrous nitrogen, than with an equal
amount of the nitric nitrogen. This was to be expected, since the avail-
ability of the nitrous nitrogen was less than. that of the nitric nitrogen,
as shown in the preceding discussion. If the availability of the nitrous

12 BULLETIN NO. 515, TEXAS AGRICULTURAL EXPERIMENT STATION

m...“ HflwH 0.2 H.w m3 Wm 3. md mowwoH E8 mfimm Ho wmm~w><
Wm mdH, odH H6 3w QmH H.m .2 .... ..+...>Hno win»... Ho. wmwpw><
.... .. Qmm mdH  Hie wdH   hmfifi 2N8
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w.  i! 3. . . . . . . . . . . -. 9w NH wnwa wmHmm
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. . . . . . . . . i i.-- Q3   w» m6 F80 2.3m

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mumow HOE Gm mGBHHH-wa Q0 0H1 QQOHU wO HSUmOR E m:H¢U!.w Qiwflkv

AVAILABILITY OF NITROUS NITROGEN TO PLANTS 13

nitrogen is calculated from the average gains in weight of the crops,
it is apparently 83% of that of nitridnitrogen when 0.1 gram is used.
If both gains and losses are considered, the nitrous nitrogen is 74% as
available as nitric nitrogen. When 0.3 gram was used the nitrous nitrogen
had only 25% of the availability of the nitric nitrogen. These may be
compared with an availability of 73% with 0.1 gram and 76% with 0.3
gram when the comparison is based on the amounts of nitrogen taken
up instead of on the gains in the weights of the crops.

There is still the question as to the utilization of the nitrous nitrogen
by the plants. That some of it was utilized was shown in the gains
in weights of the crops cited above. Further evidence is offered by the
nitrogen content of the crops.

Effect of Nitrogen Content of Crops

The gains or losses in the percentage of nitrogen in the test crops, as
compared with the crops which received no nitrogen, are given in Table 7.

With the 0.05 gram application, the percentage of nitrogen in the crop
grown with nitrite was the same as that grown with the use of the
nitrate. With the 0.1 gram application, the percentage of nitrogen was
higher in six of the eleven tests, while with the five others, it was prac-
tically the same as that in the crops produced with nitrate, or a little
lower. On an average of all the comparisons, there was slightly more nitro-
gen in the crops grown with the 0.1 gram of nitrous nitrogen than in
those grown with a corresponding amount of nitric nitrogen. In the
four comparisons with 0.3 gram of nitrogen, the plants’ grown with nitrous
nitrogen contained appreciably more nitrogen than corresponding plants
grown with nitric nitrogen, indicating the possibility of a poorer utiliza-
tion of the nitrous ‘nitrogen. Some of the plants were tested for nitrites,
but none was found in any of them.

It would appear that nitrous nitrogen in small quantities has an avail-
ability only a little lower than that of nitric nitrogen and is perhaps
equally well utilized for plant growth, but larger amounts are not so
readily taken up. The smaller plants also contain larger percentages of
nitrogen than those grown with nitrates.

Nitrification in the Sand Used

In order to test the possibility that the soils were not completely
sterilized or became contaminated during the experiment, 9 pots in
which nothing was planted were included in the 1934 experiments with
sand N0. 29208. The sand in these pots was sterilized in the same way
as the other pots and was watered with distilled water throughout the
growing period of the plants in the other pots, which was 58 days. At the
end of this time the soils were analyzed for nitrites and nitrates with the
results given in Table 8.

It is seen from this table that nitrite was present in only one of the 6
pots to which it had been added at the beginning of the test, but nitrates

14 BULLETIN NO. 515, TEXAS AGRICULTURAL EXPERIMENT STATION

8+ 3+ 8+ 21+ 3+ 3+ 8.1 ...+-.--...$mmo_ E5 mfiww we wwwb><
B. m». w? 2: 3.. mu. NH. .................... =35. wfiww we 835.3.
.... .. i. .3. 2a I.  i..- 5i Mafia
.... .. 3... 8.1 S. N? 1- -i-- E8 82w
.... .- w». S. . 5.. 2. a.  cnou 3N5
.... -- w». 2.1 $4 in. E. .1. F80 m3?
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3. -1- 8.  .... -- m». 2. 3E $5M
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.... .. 1- B.   2. 8.1 Efiimém $5»
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..... .-  2.   w». i. Baa 85m
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EM H EM m 8M H EN M EN N EM a EM mo. QOHQ hhOudhOQd-H
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93a. Gm nououfl: HQ QMSHQOHOG E Fwd“ -b Qwfifivfi

AVAILABILITY OF NITROUS NITROGEN TO PLANTS 15

were present in all 9 pots. The quantity of nitrates was less than that
originally added. Part of the nitrite which had disappeared had been con-
verted into nitrate. This would indicate either that the sand was incom-
pletely sterilized or that oxidation from other causes occurred. It also

Table 8. Nitrogen in pots at the end of the experiment

Pot Treatment — Nnlgic Nit§lous pH
P.P.M. P.P.M.
1 .2 gm. 40 p p m nitrous nitrogen 0 r 0 8.1
2 .2 gm. 40 p p m nitrous nitrogen 23 0 8.1
3 .2 gm. 40 p p m nitrous nitrogen 23 0 7.9
4 .3 gm. 60 p p m nitrous nitrogen 25 O 8.1
5 .3 gm. 60 p p m nitrous nitrogen 12 4 8.2
6 .3 gm. 60 p p m nitrous nitrogen 17 0 8.1
7 .2 gm. 40 p p m nitric nitrogen 16 0 8.1
8 .2 gm. 40 p p m nitric nitrogen 23 O 7.9
9 .2 gm. 40 p p m nitric nitrogen 43 0 7.8

would indicate that the availability of the nitrites found in the work just
reported is perhaps higher than would be the case if they were entirely
prevented from being converted into nitrates.

NITRITES IN WATER CULTURES

Since it is possible that the availability of nitrites shown in the work
reported above was higher than it really is, on account of some conversion
of nitrites to nitrates, the pot experiments were supplemented by experi-
ments with water cultures. The water solutions were sterile and frequently
renewed, so that there was little danger of possible oxidation of the nitrite-
nitrogen during the experiments. Since the plants had access to large
quantities of nitrogen, in proportion to the amounts taken up, this method
is not so well suited to measurement of the availability of nitrites or other
fertilizing materials. However, we can compare the growth of the plants
with the nitrite and the nitrate and assume that the growth is in propor-
tion to the availability of each.

The waterculture method used was that of Shive (17). After the
seeds were sprouted, three plants were mounted in a cork which rested in
the mouth of a large fruit jar. The cork also carried a glass tube
reaching to the bottom of the jar, ending in a small funnel mouth and a
siphon to carry off the excess solution. The nutrient solution was fed
slowly to the funnel in the culture jar by means of a capillary siphon tube
from a jar inverted in a petri dish. The rate of flow was regulated by
altering the height of the capillary tube and was about one liter in 24
hours. By this apparatus the culture solution is constantly renewed, so
that there is little change in pH or nitrites during the experiment. It has

16 BULLETIN NO. 515, TEXAS AGRICULTURAL EXPERIMENT STATION

the disadvantage of requiring large quantities of culture solution.
The salts used were prepared in concentrated solutions and 50 cc of each
was mixed with 12 liters of Water to make the solution used.

Relative Quantities of Nitrate and Nitrite Nitrogen
Absorbed by Corn

The object of this test was to ascertain how much nitrogen was taken
from known solutions of nitrite or nitrate during periods of 6 hours and
of 24 hours. Plants were grown according to the method of Shive in a
solution of the following composition:

Ammonium sulphate (.0042 M solution) 0.55 gram, calcium nitrate (.0075
M) 1.23 grams, monopotassium phosphate (.0021 M) 0.29 gram, mag-
nesium sulphate, cryst. (.0024 M) 0.59 gram in 1000 cc. A ferrous sulphate
0.4 per cent solution was added at the rate about 1 cc per jar every 2 or
3 days. i

Table 9. Absorption of nitric and nitrous nitrogen by corn plants in water cultures

Nitrogen absorbed
Jar Form of nitrogen
6 hours 24 hours

1 Sodium nitrate 1.3 7.8
2 Sodium nitrate 1.3 5.5
3 Sodium nitrate 0.6 7.6
Total  3.2 20.9

4 Sodium nitrite 2.0 8.6
5 Sodium nitrite 0.1 8.4
6 Sodium nitrite 1.0 6.6
Total ............................. .. 3 1 23 6

The test for the 6-hour period was performed after the seedlings had been
grown 10 days in the culture solution. Those used for the 24-hour ab-
sorption period had been grown 18 days. From 12 jars of plants 6 jars
with the best looking plants were selected for the test. The plants of
3 jars were used for absorption of nitrate and those of the other 3 for
nitrite.

The roots were thoroughly washed and the plants transferred to 1-pint
jars containing 400 cc distilled water, plus 1O cc standard sodium nitrate
or nitrite solution. At the end of the absorption period, the roots of
the plants were again washed with distilled water into the jar from which
the plants were taken. The solutions were made up to 1000 cc, and 400
cc were used for the determination of nitrogen by the zinc-ferrous sul-
fate method (5). For checks, solutions with distilled water and corres-
ponding amounts of the same nitrogen solutions were treated in the same
way. All determinations were made in duplicate.

The amount of nitrogen absorbed by the plants was estimated by sub-
tracting the amount found in the solutions that were used for absorption

AVAILABILITY OF NITROUS NITROGEN TO PLANTS 17

from the amount of nitrogen found in the checks. The results appear in
Table 9. The pH of the solutions was 5.9-6.0 before absorption for 6 hours,
and 6.2 before absorption for 24 hours. After absorption, it was about
0.2 pH higher with all for the 6 hour period, and with the nitrite for the
24 hour period, but Iabout 0.5 to 0.7 pH higher with nitrates for the
24 hour period.

The quantities of nitrogen absorbed are given in Table 9. The nitrite
nitrogen was absorbed practically as well as the nitrate nitrogen during
the 6 hour period, but the absorption of nitrites was slightly more than
that of nitrates in the 24 hour period. According to this work, the nitrite
nitrogen is absorbed by the plants to the same extent as the nitrate nitro-
gen. The absorption of nitrogen was more than 6i times as much in the
24 hour period as in the 6 hour period, though the time was only 4 times
as long.

Effect of Different Amounts of Nitrate and Nitrite Nitrogen
Upon Growth of Corn '

The nutrient solution used was based onpthat of Shive, but modified
to meet the object of the experiment. Ammonium sulfate was left out,
and the element calcium was provided as calcium chloride instead of
calcium nitrate. The solution used, as diluted, was as follows:

Monopotassium phosphate (.0021 M) 0.29 gram per liter
Magnesium sulfate . . . . . (.0024 M) 0.59 gram per liter
Calcium chloride . . . . . . (.0074 M) 0.82 gram per liter

Sodium or calcium nitrate or nitrite was added at the rate of 0.1
or 0.2 gram per liter. Ferrous sulfate solution, 0.4 per cent was
added at the rate of 1 cc per jar at intervals of 2 or 3 days. Three
jars each with three plants were used with each addition.

The first experiment in which corn was grown with sodium nitrite or
nitrate lasted 21 days from the time of mounting the seedlings on their
respective jars. A second experiment was made with calcium salts, in
which the growing period was 24 days.

The plants Which received nitrate-nitrogen made a good growth ‘and
looked much healthier than those which received nitrite-nitrogen. In the
three jars to which nutrient solution containing 0.1 gram per liter of
nitrite-nitrogen was supplied, the plants developed ‘yellow streaks on the
leaves and the roots were somewhat brownish, while the roots of the plants
receiving nitrate-nitrogen were white. During most of the growing period,
the lower leaves of most of these plants were green, but the upper ones
were yellow. At the time of harvesting, however, all the leaves had turned
green.

The plants grown in the jars to which 0.2 gram per liter of nitrite-nitrogen
was supplied looked very sickly and chlorotic throughout the experiment.
The root system of all the plants grown with nitrites was poorly developed
and heavily infected with a slimy white fungus. Whether the retardation

18 BULLETIN NO. 515, TEXAS AGRICULTURAL EXPERIMENT STATION

o ". ".0. 2. 1H M." ". no.2" H09 .7" EM N. dab? 522.6 ""
oo" 2N ".0 Q3 9mm“ Q3. 5.2 n03" H09 Z SM N. 322a EESQO w .m J
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co" c6" m3. w."" 53w 0.2. Q3; .33" H2" Z 8M N. .33.“: Esnsw \ w 6 J.
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.23.... .3 ~58.

AVAILABILITY OF NITROUS NITROGEN TO PLANTS 19

of the growth of the plants was due to the development of the above
fungus or due to unavailability of the nitrite-nitrogen is not known.

The results of this work, which appear in Table 10, show that the
growth with nitrite-nitrogen was less than with nitrate. This is also
seen in Figure 1. With 0.1 gram nitrogen per liter, the production of
dry matter with sodium nitrite was 23% of that with sodium nitrate, and
the growth with calcium nitrite was 21% of that with calcium nitrate.
With‘ 0.2 gram nitrogen per liter, the corresponding growths were 12%
and practically zero, respectively.

Relation of Degree of Acidity of the Solution on the Growth of Corn,
Cotton and Oats with Nitrate and Nitrite Nitrogen

In this part of the study, plants were grown with nutrient solutions
containing 0.1 gram nitrogen in the form of sodium nitrate and nitrite,
made up to different degrees of acidity by additions of sodium hydroxide

Figure. 1. Corn in water cultures with 0.1 gm and 0.2 gm nitrate nitrogen per liter
(Na) and corresponding amounts of nitrite nitrogen (Ni).

or sulphuric acid, approximately pH 4.0, 6.0, and 8.0. Unfortunately,
however, these pH values were found to change during the growing period,
especially those solutions which were originally made to pH 8.0. These
changes were apparently due in part to the precipitation of the phosphates
in the nutrient solutions. Some difficulty was also encountered from the

20 BULLETIN NO. 515, TEXAS AGRICULTURAL EXPERIMENT STATION

3 w.» m; m.N Q3 v.2“ “.3 m6 vfiafii Esmwom NH n:
5 9m. HA ma Q5. HdN wSN v6 “its? 553cm m. d
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AVAILABILITY OF NITROUS NITROGEN TO PLANTS 21

plugging of the siphon by the precipitated phosphate. This difficulty,
however, was overcome to some extent by the filtration of the nutrient
solutions before use.

There was also difficulty in the preparation of the nutrient solution
containing nitrite-nitrogen at pH 4.0. Preliminary tests showed that this
pH value could not be secured, even with large additions of sulfuric acid.
For this reason, the amount of acid added was the same as that in those
solutions containing nitrate-nitrogen made up to pH 4.0.

Excessive heat in the greenhouse affected the growth of the plants, since
the growing period of this series was from June 14 to July 13. Since it

Figure 2. Cotton in water culture with nitrate nitrogen (Na) and ‘nitrite nitrogen
(Ni) at pH 4.0, 5.0, 6.0, and 6.8.

was quite evident that the heat had retarded, to some extent, the growth
of the plants in the whole series, the experiment was repeated during
September when temperatures were not so high as during June and July.

The results of these two tests with corn appear in Table 11 and indicate
that nitrates are taken up by corn in greater quantities at pH 4.0 than at
pH 6.0 to 8.0, while nitrites are taken up in the reverse order. The de-
crease in the phosphates by precipitation may have caused a low growth
with the nitrates.

An experiment was made with cotton similar to that with corn, except
that less sodium hydroxide was added to the nutrient solutions up to the
point where phosphorus precipitation began to take place, about pH 6.8.
However, the solution was unstable, since partial precipitation took place

22 BULLETIN NO. 515, TEXAS AGRICULTURAL EXPERIMENT STATION

mu m6 3. e6 m6 m6 6H 64. uahvériumwom . NH .HH
mm g m6 v6 wd RH H.H 6.6-6.6 @626: 828w 6 .6
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AVAILABILITY OF NITROUS NITROGEN TO PLANTS 23

in the greenhouse, so that the pH would drop again to 5.9 to 6.0.

The results of this test, which appear in Table 12, show that nitrites
produce little growth of cotton at pH 4.2-4.4, but produce more growth
as the pH increases towards alkalinity. More work is needed to decide
whether or not nitrites produce a good growth at pH 7.0 to 8.0.

In an experiment with oats, the nutrient solutions used were like those
used by Davidson and Shive (1) for the growth of peach trees.

The solution used was as follows:

Monopotassium phosphate (.00633 M) 0.86 gram per liter

Magnesium sulfate . . . . . (.00711 M) 0.85 gram per liter
Calcium chloride . . . . . . (.0074 M) 0.82 gram per liter
Sodium nitrate or nitrites . . . . . . . .0.1 gm N per liter

Ferrous sulfate was added as in the work already mentioned.

The precipitation of phosphates could not be avoided upon the addition
of the sodium hydroxide for making up to pH 8.0. Hence, as in the
previous work, the phosphate precipitates were filtered off before trans-
ferring the solutions to their respective jars.

Results of this series appear in Table 12 and show that nitrites produce
little growth of oats at pH 4.6 to 4.8'and sowewhat better growth at
higher pH values. The oat plants assimilate nitrates in the same manner
as corn at pH 4.0 and 6.0, but they produce less growth as the pH value
of the nutrient solution increases toward alkalinity.

The relative dry weights of the plants produced in all the experiments
are shown in Table 13. lVith nitrates, the dry matter produced is highest
at pH 3.9-5.4, and lowest at pH 6.4-7.7. With nitrites, the dry matter
produced is lowest at pH 3.9-5.4 and highest at 6.4-7.7. The low crop
with nitrates at pH 6.4-7.7 may be in part due to the precipitation of
calcium phosphate from the solution.

AVAILABILITY OF NITRITES AS MEASURED
BY GROWTH IN WATER CULTURES

Water cultures have not been used for estimation of the availability
of fertilizing materials because some of the materials are not soluble in

Table 13. Relative effect of uH unon the dry weight of crons grown in water culture with
nitrate and with nitrite nitrogen

 

pH 3.9-5.4 DH 5.7-6.0 DH 6.4-7.7

Corn

Nitrate .......................... .. 100 55 47

Nitrite ........................ ._ 3 4 57
Corn

Nitrate .......................... ..| 100 80 37

Nitrite ....................... .. ’ 10 31 40
Cotton

Nitrate ......................... ._ 100 63

Nitrite ................... ..  0 1 1 5
Oats

Nitrate .......................... .. 100 118 25

Nitrite ....................... ..| 4 42 28

24 BULLETIN NO. 515, TEXAS AGRICULTURAL EXPERIMENT STATION

water and must undergo changes before they are taken up by other plants,
and also because the quantity of nutrient supplied to the plant is usually
considerably in excess of that taken up. However, it is possible to assume
that When equal quantities of substances in the nutrient are furnished

separately to plants, the growth of

the plants is in proportion to the Table 14. Availability of nitrite nitrogen
at pH 6 based on total growth

availability of the nutrients. We have in water culture experiments

made this assumption and calculated (nitrate at 100)

the availability of the nitrite nitrogen | |

from the results presented in the pre-  || j gizfi g2;  l 

ceding pages. 80m l  gram per liter l 
The quantity of dry matter pro- 88%.,“  Ii 52$ 32$  { 

' 1 ' O 0n . gram per 1 GT

duced by the nitiate is placed at 160 Oats I l gram per liter I 34

and the availability of the nitrite is l I

calculated from the dry matter pro- l Average """""""" " 21

duced by the plants grown at the  l I;  3::  I 1g

l

same time and under the same con-
ditions.

Table 14 shows the availability of the nitrite nitrogen at the pH of
approximately 6 for corn, cotton, and oats, with 0.1 gram nitrogen per
liter, and also for corn with 0.2 gram per liter. The availability of the
nitrite is 7 to 37% with corn, 11 to 12% with cotton, and 34% with oats
when 0.1 gram nitrogen per liter was used. With corn growing in 0.2
gram per liter the availability was 12 to 0%, which was much less than
with 0.1 gram.

In Table 15 the availability of the

nitrite nitrogen at different degrees Table 15.‘ Relative availability 0f Ilitfifl!
nitrogen in water cultures

of acidity (pH) are given. It is seen (nitrate=100)

in this table that the availability _
is lowest at a pH of 3.9-5.4, and a PH Rvsijlglfte
little higher at 5.7 to 6.0, while at
6.4 to 7.7 it is equal to that of the Co" gag-g g
nitrate in the two tests with corn and 614-717 120
the test with oats. In the test with 0°“ 33:33 g7)
cotton a pH of 6.4 to 7.7 was not 614-717 105
secured. Cotton $13123? 1(1)
A t1 th nitrit itro e is . 5'94“) 12
PDQ-Ten Y e e I1 g‘ I1 Oath 4.6-4.8 4
taken up by plants just as well as 2122215 151*;
nitrate nitrogen in alkaline solution.

Our nitrification work has shown

that nitrites are more likely to be produced in alkaline soils than in
soils with a lower degree of acidity (pH). The soils in which they are
likely to be produced are those in which they are not likely to be toxic in
small amounts, if we can assume that the results of the water cultures
apply to soils.

AVAILABILITY OF NITROUS NITROGEN T0 PLANTS 25
SUMMARY

In pot tests with soils, solutions of sodium nitrite applied to the roots
of plants were more toxic than corresponding solutions of sodium nitrate.
Little toxicity was found when the sodium nitrite was distributed through
the soil. The availability of the nitrous nitrogen in sodium nitrite was
less than that of the nitric nitrogen in sodium nitrate in 21 of the 24 com-
parisons conducted by means of pot experiments. In 11 comparisons with
one-tenth gram nitric nitrogen in 5,000 grams of soil, 69.4% of nitric
nitrogen was recovered as compared with 51.7% of the nitrous nitrogen.
In 2 comparisons with three-tenths gram nitrous nitrogen the avail-
ability was 50.8% as compared with 66.8% for nitric nitrogen. Small
amounts of nitrous nitrogen were utilized just as well as nitric nitrogen,
but larger amounts of nitrous nitrogen were not as well utilized. With
three-tenths gram in 5,000 grams soil the nitrogen taken up from nitrous
nitrogen was 76% of that of the nitric nitrogen, but the total plant growth
produced by nitrous nitrogen was only 25% of that produced by the nitric
nitrogen.

Nitrites added to pots of sterilized soils kept under the same conditions
as those in which the plants were grown were partly changed to nitrates
and partly disappear/ed. _

Corn took up approximately equal quantities of nitrites and nitrates from
water cultures during periods both of 6 hours and of 24 hours.

The production of dry matter of corn in water culture with sodium
nitrite was 23% of that with sodium ‘nitrate, and with calcium nitrite
was 21% of that with calcium nitrate when 0.1 gram per liter was used.
When 0.2 gram nitrogen was used, the growth was smaller with the sodium
salts and larger with the calcium salts than when 0.1 gram per liter
was used.

When different degrees of acidity were used, corn made the greatest
growth at a pH of 3.9-4.1 and the lowest growth with pH of 6.4-7.7 with
the nitrate salts, while with the nitrite salts the lowest growth was made

- at pH 3.9-4.1, and the highest at 6.6-7.7. With cotton and oats, the nitrite

produced the smallest growth in the more acid solution.

If the- growth of the plants is taken as a measure of availability, the
availability of the nitrite to corn, cotton, and oats at pH 6 was approxi-
mately 21% of that of nitrates. At pH 3.9-5.4, the average availability
of the nitrite was 4, while at pH 6.4-7.7, it was approximately 112, com-
pared with nitrates at 100. The comparative availability of nitrate and
nitrites in water cultures depends upon the pH of the solution. _

When the results of the pot tests are compared with the results of the
water cultures, it appears probable that the availability secured in the
pot experiments for soils of the pH used is approximately correct.

26

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BULLETIN NO. 515, TEXAS AGRICULTURAL EXPERIMENT STATION

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AVAILABILITY OF NITROUS NITROGEN TO PLANTS 27

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