226 
Journal of Agricultural Research 
Vol. IX, No. 7 
The nitrate content of the soil in plot R, like the other soils which 
have received no nitrogenous fertilizers, is very low. At the time of the 
first irrigation the amount found in the upper 6 inches amounted to only 
0.34 mgm. The maximum quantity found within reach of the roots 
amounted to only 0.21 mgm., and in many cases less than 0.10 mgm. 
was found. After the second irrigation the nitric nitrogen in the upper 
6 inches 18 inches from the furrows amounted to 2.5 mgm., while only 
0.29 mgm. was found 9 inches from the furrows (fig. 13). 
Plot S lies immediately adjacent to plot R, and the effect of the dried 
blood added has evidently caused a very marked increase in the nitrate 
content of the soil. At the time of the first irrigation the upper 6 inches 
contained 6.36 mgm., the layer from 6 to 18 inches 2.19 mgm., the layer 
from 18 to 30 inches 1.10 mgm., and the layer from 30 to 42 inches 1.09 
mgm. Thus, it is seen that at the beginning of the irrigation season 
there was a very satisfactory nitrate supply in this soil, and that the 
lateral distribution was apparently quite uniform before the first irri- 
0"-X9" 
M— 
a 
1 — --—Ln __n .ard 1 — —n 
/$r /&- *tw /$r &&& 
mo. or//w&tr/cw 
Fig. 13.—Diagram showing the distribution of nitrates in plot R before and after irrigations. Season of 
1916. 
gation, but quite uneven during the irrigation season. However, the 
nitric nitrogen showed a more satisfactory distribution in this soil during 
the irrigation season than in plot C, which received the same treatment, 
but which was a lighter soil (fig. 14). 
At the time of the first irrigation the nitric nitrogen in plot U amounted 
to 1.31 mgm. in the upper 6 inches, 0.52 mgm. at a depth of 6 to 18 inches, 
and at the lower depths to less than 0.20 mgm. During the irrigation 
season the amount of nitric nitrogen found in the upper 6 inches varied 
from 0.88 to 11.8 mgm. At a depth of 6 to 18 inches the maximum amount 
found amounted to 3.05 mgm., while the minimum amount found at 
this depth was 0.25 mgm. (fig. 15). 
The data presented in figures 3 to 16 show conclusively that the fur¬ 
row system of irrigation causes a very uneven distribution of nitric 
nitrogen in soils; but as the work progressed it became apparent that 
samples drawn from the bottom of the furrows, 9 and 18 inches from the 
furrows, were not sufficient to show the maximum effect of the irriga¬ 
tion, as the highest concentration of nitrates did not always occur midway 
