May 28,1917 
Influence of Crop, Season , Water on Soil Bacteria 
3i9 
the speed with which the protein-forming organisms work. Further 
more, while the increased temperature of summer increases the activity 
of both classes of organisms, the speed of the latter, is accelerated to a 
much greater extent by heat than is the speed of the former. More¬ 
over, both classes of organisms are sensitive to cold, but it would appear 
that those which bring about synthetic reactions are much more sensi¬ 
tive than are those which bring about the analytic change. We there¬ 
fore have an accumulation of nitrates during the cold seasons and a dis¬ 
appearance during the warmer months of the year. These facts would be 
in keeping with the findings of Conn, Brown, and others who have 
noticed that cold increases the nitrifying powers of the soil. 
Table XVIII .—Nitric nitrogen in soil with various crops and receiving no irrigation 
water—Average for three years 
Period. 
Spring.. 
Do.. 
Do.. 
Do.. 
Do.. 
Summer 
Do.. 
Do.. 
Do.. 
Do.. 
Do 
Do 
Do 
Do 
[Results expressed as pounds per acre] 
Crop. 
Depth of soil. 
istfoot. 
2 d foot. 
3 d foot. 
4 th foot. 
5 th foot. 
6 th foot. 
Alfalfa. 
10. 9 
S* 1 
II. 4 
2.2 
9*3 
6. 0 
Oats. 
9.1 
5*9 
4. O 
6. 1 
10. 7 
< 5.3 
Com. 
12. 0 
4.1 
1.9 
2. 5 
3*4 
3*5 
Potatoes. 
10. 9 
29.0 
43*6 
46.4 
38*5 
27.9 
Fallow. 
18. 9 
39*6 
31*9 
14. 8 
21. 7 
16.1 
Alfalfa. 
3*3 
8.8 
2. 2 
1.4 
2. 6 
1.0 
Oats. 
3*3 
1. 6 
'i -5 
1. 6 
1. 6 
.8 
Com. 
3*3 
3 * 1 
2.9 
2. 6 
3*2 
2. 2 
Potatoes. 
25*9 
8.9 
* 7*5 
25.1 
18. 4 
17.9 
Fallow. 
15*5 
9*7 
8.2 
9*7 
13.6 
16.1 
Alfalfa. 
19*5 
7.0 
6*5 
3 *o 
2.1 
1.1 
Oats. 
6. 7 
3*9 
3*7 
3*3 
2.9 
2. 8 
Com. 
11. 2 
4. 6 
3 * 1 
3 * 5 
5*° 
5*9 
Potatoes. 
34*6 
17. 6 
9.8 
5 
19.1 
9.6 
Fallow. 
3 i* 5 
17. 6 
18.1 
15*9 
i 1 * 5 
12.3 
Total. 
44.9 
42. I 
27.4 
196.3 
143.O 
19-3 
zo. 4 
I 7 * 3 
” 3-7 
72. 8 
39-2 
23-3 
33-3 
102. 2 
106. 9 
If we average the nitric nitrogen in the plots growing the various 
crops, we find a marked difference in the quantity found in the various 
plots (Table XIX). 
Table XIX .—Average nitric nitrogen in the plots growing various crops 
[Results expressed as pounds per acre] 
Crop. 
Time of sampling. 
Average. 
Spring. 
Summer. 
Fall. 
Alfalfa. 
22.3 
15*8 
32.8 
23.6 
Oats. 
35*7 
14. I 
20. 6 
23*5 
Com. 
24. 8 
18. 9 
22. 0 
21.9 
Potatoes. 
81. 1 
60.8 
54.2 
6S- 3 
Fallow. 
81. S 
53-6 
62.6 
65-9 
