3 H 
Journal of Agricultural Research 
Vol. IX, No, 9 
than in the fall, thus showing a gain for the printer months and a loss 
for the summer months. This loss can not be due to the water applied, 
because it is most pronounced in the unirrigated plots and probably 
represents the quantity transferred into complex proteins by the bacteria. 
Taken as a whole, the results would tend to indicate that the irrigation 
water had decreased, instead of accelerating the formation of nitric 
nitrogen in these plots. When we take the average total amount of 
nitric nitrogen in all cropped and fallow plots receiving the same amount 
of irrigation water, we note a pronounced difference in the quantity of 
nitric nitrogen in the plots receiving varying quantities of water. These 
averages are given in Table XIV. 
Table XIV .—Average quantity of nitric nitrogen found in the plots receiving the various 
amounts of irrigation water 
[Results expressed as pounds] 
Water applied (inches). 
Spring. 
Summer. 
Fall. 
Average. 
57 .q. 
31.8 
34.0 
39*6 
90-7 
26.2 
32-s 
* 5-3 
46. 7 
27 *3 
34*3 
3 i- * 
61.5 
28. 4 
33-6 
32, 0 
66.3 
2K.O ... 
Itr.o.. 
None. 
The quantity of nitric nitrogen found within the surface 6 feet of 
soil decreases as the water applied increases. The difference is very 
noticeable in all of the plots in the spring. During the summer and fall 
all irrigated plots tend to reach a similar concentration of nitric nitrogen. 
But even then there is twice as much in the unirrigated as in the irrigated, 
and during the spring there is three times as much in the nonirrigated as 
in the plot receiving 37.5 inches of water. 
In previously reported work (56) we have shown that the application 
of irrigation water increases the quantity of nitric nitrogen actually 
formed within the soil; hence, the difference between that found within 
the irrigated and the unirrigated soils must represent the quantity removed 
by the crop plus that washed to a region below 6 feet in the soil. These 
results prove conclusively that this is no small quantity, especially when 
large quantities of water are applied to the soil. Hence, the excessive 
use of irrigation water is not only a waste but it decreases the yield upon 
a given soil; and this latter effect is due in all probability to the rapid 
removal of the soluble nitrates beyond the reach of the growing plant. 
INFLUENCE OF THE CROP ON THE NITROGEN OF THE SOIL 
The experiment was so planned that it would also give information 
on the influence of crop upon the nitric nitrogen of the soil. Therefore, 
the results have been rearranged so as to compare plots receiving the 
same quantity of water but growing different crops. In these the 
variable is the crop, while the water remains a constant. 
