May 28,1917 
Influence of Crop, Season , Water on Soil Bacteria 
3ii 
we note in the fall is an accumulation of more nitrates in the surface 
feet. It is interesting to note that each plot gains considerable nitric 
nitrogen during the winter months. The gain is least in the plot which 
received 37.5 inches of water, but is quite uniform in each of the others. 
The summarized results of the nitrogen removed in the crop, together 
with the original nitric nitrogen present in the soil and the amount 
formed during the irrigation season, are recorded in Table X. 
Table x. —Summary of nitrogen transformations in oat land 
[Results expressed in pounds! 
Character of nitrogen. 
Water applied. 
inches. 
inches. 
inches. 
None. 
Nitrogen removed in crop. 
Nitrogen in soil in spring. 
Nitrogen in soil in fall. 
Original soil nitrogen removed. 
Nitrogen formed during season. 
Excess of nitric nitrogen in irrigated plots. 
Excess per acre-inch of water. 
s 9 - 5 
3 1 - 7 
20. 4 
ir -3 
78. 2 
33 * So 
.88 
83-9 
35 - 5 
18.3 
17. 2 
66. 7 
21.5 
.86 
71.7 
33 ' 4 
20. 6 
12.8 
5 8 *9 
13-7 
.91 
64. O 
42. I 
2 3 * 3 
18.8 
45-2 
From this it may be seen that the greatest quantity of nitric nitrogen 
was produced in the plot which received the greatest quantity of water, 
but the amount per acre-inch of water is slightly higher in the plot which 
received only 15 inches of water. The actual difference in the quantity 
of nitrogen produced in the various plots would be even greater than 
the figures herein represent them to be, for the tendency would be for 
the larger quantities of water to carry some of the nitric nitrogen below 
the sixth foot. It is important to note that the order of effectiveness 
was found by us to be practically the same as here reported when we 
sampled the plots to a depth of 10 feet; yet in this work they are more 
regular than in previously reported results. 
4.—CORN LAND 
There were four plots in this series. One received 37.5 inches of water, 
one 25 inches, one 15 inches, and one was unirrigated. With the excep¬ 
tion of the amounts of water applied, the plots were all uniformly 
handled throughout the experiment. The average results for the three 
years are given in Table XI. 
The nitric nitrogen is high in the surface foot of all the plots in the 
spring. This is especially the case where only 15 inches or no irrigation 
water was applied, but in the summer it becomes very low. This is due 
mainly to the removal of the nitric nitrogen by the rapidly growing 
plant. The water, however, does play some part, for we find that the 
nitric nitrogen of the surface foot disappears more rapidly from the 
