May 2$, 1917 
Influence of Crop , Season , Water on Soil Bacteria * 317 
find the greater part of it concentrated in the surface-foot sections. 
During the summer it is more evenly distributed throughout the 6 feet. 
The fallow gains considerable nitric nitrogen during the early summer, 
while each of the other soils shows a loss, which in the case of the oat 
soil is quite pronounced. Prior to the summer sampling it appears that 
the water applied has not been sufficient to carry much of the nitric 
nitrogen below the sixth foot, but during the time which elapsed between 
the summer and fall sampling there was a loss from the fallow soil, with 
a slight gain in each of the other soils. Moreover, these results, taken in 
connection with those previously published by us, where samples were 
taken to a depth of 10 feet, indicate that no small quantity of the nitric 
nitrogen is carried below the sixth-foot level. Hence, the continuous 
use of this quantity of water on these plots would result in an unneces¬ 
sary loss of nitric nitrogen from the soil. The fallow, potato, and corn 
land contains practically the same quantity of nitric nitrogen in the soil 
during the spring as during the fall, while the alfalfa and oats show a 
wide variation. 
plots receiving 15 inches op irrigation water 
Each of the plots in this series received 15 inches of irrigation water. 
The treatment of each plot was as nearly similar as compatible with the 
various crops growing upon them; hence, any difference in nitric nitro¬ 
gen noted should be due to the crops. The average summarized results 
for the three years are given in Table XVII. 
Table XVII.— Nitric nitrogen in soil with various crops and receiving 15 inches of irri¬ 
gation water—Average for three years 
[Results expressed as pounds per acrej 
Period. 
Spring.. 
Do.. 
Do.. 
Do.. 
Do.. 
Summer 
Do.. 
Do.. 
Do.. 
Do.. 
Fall 
Do.. 
Do.. 
Do., 
Do., 
Crop. 
Depth of soil. 
Total. 
istfoot. 
2 d foot. 
3 d foot. 
4 th foot. 
5 th foot. 
6 th foot. 
Alfalfa. 
3*4 
0.9 
11. 6 
3*3 
1. 6 
1.9 
22. 7 
Oats. 
7.6 
6.9 
9.6 
4. 6 
i *7 
3 *o 
33*4 
Com. 
12. 3 
&5 
4. 1 
2. 0 
1. 6 
1.9 
30.4 
Potatoes. 
20. 5 
8.7 
4. 0 
4. 0 
3 * 1 
4. 0 
44*3 
Fallow. 
10. 4 
15.6 
9.2 
9. 1 
13. 6 
9*5 
67.4 
Alfalfa. 
5*4 
.8 
2. 1 
1. 7 
3 * 1 
1.4 
* 
Oats. 
5 * 1 
3*8 
3 * 7 
i *7 
3 *o 
.8 
18. 1 
Com. 
1. 4 
5 * 2 
3 * 7 
2 * 5 
3*2 
3*3 
19*3 
Potatoes. 
16. 1 
15. 2 
7. 2 
3 * 2 
3 *o 
2.4 
47 - 1 
Fallow. 
8.4 
6. 2 
4-4 
2. 6 
2. 1 
3 * 1 
26.8 
Alfalfa. 
10. 7 
10. 4 
4.4 
23 
2.9 
1.8 
32.5 
Oats. 
4.2 
3*3 
4. 1 
3*4 
2.9 
2*7 
20. 6 
Com. 
5 *S 
2 *5 
3 * 2 
3*o 
3*2 
3*2 
20. 9 
Potatoes. 
10. 0 
3* 7 
2* 5 
6.6 
7.2 
4.4 
35*3 
Fallow. 
10. 1 
7*4 
<5-3 
7.2 
7* 7 
7*3 
46. 0 
