552 
Journal of Agricultural Research 
Vol. XXXI, No. 6 
ration. This soil is very acid, having a P H value of 4.9. It also 
contains a large amount of easily replaceable iron, aluminum, and 
manganese. It is possible that in this case the nitrifying organisms 
are inhibited by the unfavorable conditions and that considerable 
amounts of ammonia can accumulate in the soil. 
Table III .—Effeci of temperature and moisture on the ammonia and nitrate content 
of four soils 
Soil type 
Acidity 
Total 
nitrogen 
in sur¬ 
face %% 
inches 
Nitrogen as nitrate 
At 
begin¬ 
ning 
At end of incubation 
25 per cent 
saturation 
.50 per cent 
saturation 
75 per cent 
saturation 
15° C. 
30° C. 
15° C. 
30° C. 
15° C. 
30° C. 
Webster clay loam_ 
Knox silt loam_ 
Shelby loam... _ 
Marion silt loam_ 
Not acid.. 
_do_ 
Strong_ 
_do_ 
Pounds 
, 8,630 
1,370 
3,380 
1,990 
P.p.m.® 
13.2 
4.9 
12.5 
11.2 
P. p. m. 
50.4 
10.8 
45.8 
19.8 
P. p. m. 
65.2 
16.6 
90.1 
38.9 
P. p. m. 
55.4 
13.9 
56.4 
22.1 
P. p. m. 
86.6 
20.8 
103.5 
76.8 
P. p. m. 
70.8 
14.7 
78.3 
28.7 
P. p. m. 
83.2 
15.9 
91.2 
69.2 
Soil type 
Acidity 
Ammonia content 
At 
begin¬ 
ning 
At end of incubation 
25 per cent 
saturation 
50 per cent 
saturation 
75 per cent 
saturation 
15° C. 
30° C. 
15° C. 
30° C. 
15° C. 
30° C. 
Webster clay loam_ 
Knox silt loam... 
Shelby loam___ 
Marion silt loam.. 
Not acid_ 
_do_ 
Strong.. 
_do_ 
P. p. m. 
10.22 
14.96 
20.19 
67.32 
P. p. m. 
5.1 
.7 
5.2 
74.8 
P. p. m. 
3.5 
1.4 
2.7 
67.4 
P. p. m. 
5.0 
.9 
3.9 
74.8 
P. p. m. 
3.7 
3.4 
2.4 
41.2 
P. p. m. 
3.4 
.34 
3.4 
65.9 
P. p. m. 
3. 7 
1.3 
3.0 
41.0 
* P. p. m.=parts per million. 
During the past season the large amount of rain and very cool 
weather have kept the soils fairly cold. A large number of field soils 
have been examined and the ammonia content of none of them has 
been greater than 40 parts per million, while most of them contained 
less than 10 to 15 parts per million. 
The accumulation of ammonia in soils evidently depends upon the 
rate of protein hydrolysis and the rate of nitrification, just as the 
rate of nitrification depends upon ammonification (S), except when 
ammonia is added to the soil, and the rate at which the nitrates are 
used by plants and microorganisms. For this reason a method 
which would determine the amount of easily hydrolyzable protein 
might give much more accurate information in regard to the availa¬ 
bility of soil nitrogen than nitrification tests which are merely an 
equilibrium depending upon the rate of nitrate formation and con¬ 
sumption, and the results could be determined very quickly. Fur¬ 
ther investigation is in progress to determine whether such an ana¬ 
lytical procedure can be developed which will correlate with crop 
growth. 
