Sept. 15, 1925 
The Ammonia Content of Soil 
551 
It may be that the ammonia content of soils is influenced quite 
largely by soil management. Because the treatment of the soils 
used in Table I was not known, a second series of soils was collected. 
Eleven samples were taken from plots receiving no treatment on 
several of the outlying experimental fields, one sample was taken 
from an onion field near Rudd, four samples were secured near Logan, 
and a sample of shale was secured near Fairfield. 
The results of these analyses are given in Table II. The ammonia 
content was not affected by the crop, neither was it correlated with 
total nitrogen or acidity. Soil No. 2, which was growing a crop of 
onions, had a very high nitrate content; and the ammonia content 
also was large. The nitrate content varied with the crop grown. 
It was low in soils growing small grain and higher in case of soils, 
growing legumes and corn u). 
Table II.— Ammonia, nitrate, total nitrogen content, and acidity of several field 
soils growing various crops 
Am¬ 
monia 
P.p.m. 
8.2 
20.6 
12.2 
9.3 
7.1 
4.0 
5.6 
6.7 
7.9 
9.3 
7.1 
6.0 
16.8 
5.3 
16.8 
4.3 
5.6 
° P. p. m.=parts per million. 
b Subsurface. 
«Subsoil. 
In the third experiment a study was made on the effect of tempera¬ 
ture and moisture on the ammonia content of four soils which varied 
widely in reaction and total nitrogen content. Two series of each 
soil were made up to 25 per cent, 50 per cent, and 75 per cent satura¬ 
tion with distilled water and incubated for 6 weeks. One series was 
kept at a temperature of 30° C. and the other series at 15°. The 
results are given in Table III. They do not agree with those pre¬ 
sented by Hutchinson (5), who found that ammonia accumulated 
more rapidly than nitrates at a temperature of 25° to 30°. 
It was found in all cases but one that the ammonia content of these 
soils was lower at the end of the incubation period than at the 
beginning, while the nitrate content increased on incubation. In 
case of the Marion silt loam both the nitrates and the ammonia 
increased at 15° C., but at 30° the ammonia content decreased when 
the soils were kept at a moisture content of 50 and 75 per cent satu- 
S am¬ 
ple 
No. 
Soil type 
Webster silt loam. 
Floyd silt loam... 
Tama silt loam... 
Grundy silt loam. 
_do. *. 
-do. c _ 
_do_.-_ 
Marshall silt loam. 
Putnam silt loam.. 
_do b .. 
Clinton silt loam.. 
Marshall silt loam. 
_do_ 
_do_ 
Marion silt loam. 
:_do_ 
Shale__ 
Source 
Ames, Iowa_ 
Rudd, Iowa. 
Newton, Iowa_ 
Mount Pleasant, 
Iowa. 
_do_ 
_do_ 
Cedar, Iowa_ 
Logan, Iowa_ 
Farmington, Iowa. 
_do_ 
Keosauqua, Iowa. 
Logan, Iowa_ 
_do.. 
_do.. 
Lowell, Iowa.l_ 
West Point, Iowa. 
Fairfield, Iowa_ 
Crop 
Oats.. 
Onions_ 
Corn. 
...do_ 
...do_ 
...do_ 
Wheat.... 
Alfalfa.... 
Oats_ 
...do.. 
...do_ 
...do- 
Sweet clo¬ 
ver. 
Rye_ 
Corn_ 
Oats.. 
None_ 
Acidity 
Not acid. 
Strong- 
Medium_ 
Strong. 
Medium+_ 
Medium_ 
Strong- 
Very slight_ 
Medium_ 
Strong. 
-do_ 
Not acid. 
.do_ 
.do_ 
Medium-}-_ 
Medium_ 
Very strong.__ 
Total 
nitro¬ 
gen in 
m 
inches 
of soil 
Pounds 
7,870 
6,460 
4.680 
4,660 
2.290 
1.290 
3,850 
3,430 
2,700 
3,050 
2,990 
2,900 
2,800 
2,740 
2.680 
1,880 
500 
Nitro¬ 
gen as 
nitrate 
P.p.m. 0 
1.0 
153.6 
16.8 
28.0 
9.0 
8.8 
1.6 
8.6 
8.0 
5.6 
1.6 
12.8 
12.8 
4.0 
24.4 
2.6 
None. 
