May *8,1917 Influence of Crop , Season , Heater on Soil Bacteria 
313 
These results would lead us to believe that the quantity of nitric 
nitrogen formed during the season was much less where 37.5 inches of 
water were applied than where 25 inches, 15 inches, and no water was 
used. This is probably not correct, but in this plot much nitric nitrogen 
has been removed in the drain waters. This set of plots differs markedly 
from all others, in that no more nitric nitrogen is accounted for in the 
irrigated than in the nonirrigated soil. Nor do these results correspond 
with those previously published by us; however, the variation may be 
due to the difference in depth of sampling, for in previously reported 
results we have sampled to a depth of 10 feet, while here we have sampled 
to a depth of only 6. In this latter case, apparently, the total herein 
reported does not represent all the nitric nitrogen formed within the 
soil; but during the summer, where the heavier applications of irrigation 
water are made, much of the nitric nitrogen is carried below 6 feet. 
5. —fallow son. 
Four plots were kept fallow throughout the experiment. One of these 
received 37.5 inches of water, one 25 inches, one 15 inches, while one was 
unirrigated. With the exception of water applied, the plots were all 
treated the same. The summarized results for the three years, reported 
as pounds per acre, are given in Table XIII. 
Table XIII .—Nitric nitrogen in fallow land—average for three years 
[Results expressed as pounds per acre) 
Plot No. 
Period. 
Water ap¬ 
plied (five 
applica¬ 
tions). 
Depth of soil. 
Total, 
1 st foot. 
sdioot. 
3 d foot. 
4 th foot. 
5 th foot. 
6 th foot. 
Inches. 
39. 
Spring... . 
37-5 
15.6 
145 
10. 7 
5*5 
7.2 
5*9 
59-4 
40. ; •. • 
25.0 
10. 1 
6. 0 
4. 8 
5-5 
10* 5 
19.4 
$6-3 
41 . 
* 5*0 
10. 4 
15.6 
9.2 
9.1 
13*6 
9* 5 
67.4 
42 . 
None. 
1$. 9 
39*6 
31.9 
14.8 
21. 7 
16.1 
i 43 -o 
39. 
Summer... 
37*5 
4* S 
6.9 
5-3 
9*4 
8.6 
7.2 
42. 2 
40. 
25.0 
3*5 
13*4 
I 3 *i 
15*2 
19.6 
7*9 
72.7 
4 i . 
15.0 
8.4 
6. 2 
14.4 
2. 6 
2.1 
3 * 1 
26.8 
42 . 
None. 
i 5*5 
9*7 
8.2 
9*7 
13.6 
16.1 
72.8 
39... 
Fall. 
37-5 
9.4 
7.2 
7*8 
9.0 
6*3 
5*3 
45 *o 
40 . 
25.0 
16.5 
7*9 
9*7 
6. 0 
7.8 
4-5 
52.4 
4 i. 
. r 5 *° 
10.1 
7*4 
6-3 
7.2 
7*7 
7*3 
46. 0 
42 . 
None. 
3 i-S 
17. 6 
18.1 
15*9 
“*5 
12.3 
106. 9 
The quantity of nitric nitrogen in the surface foot of all the plots is 
high in the spring but greatly decreases in the surface foot of all the 
irrigated plots in the summer. There is, however, a reconcentration of 
the nitric nitrogen in the surface during the fall. This is very pronounced 
in the case of the plot which did not receive irrigation water. The total 
quantity of nitric nitrogen in each specific plot is higher in the spring 
