May as, 1917 Influence of Crop , Season , Heater Bacteria 337 
Large quantities of nitric nitrogen disappeared from the fallow soil 
during the summer months. This is attributed to the growth of bacteria, 
which transforms it into protein substances and not to denitrification. 
The larger applications of irrigation, 37.5 and 25 inches of water, carry 
much of the nitric nitrogen beyond the sphere of action of the plant, 
and this accounts for the decrease in crop yield, which is often noted when 
excessive quantities of irrigation waters are applied to a soil. 
The application of water to a soil depresses the number of organisms 
which will develop upon synthetic agar in alfalfa, oats, and potato soil, 
but increases them in fallow. The results obtained with the corn are 
irregular. 
The ammonifying powers of all the soil, except the alfalfa, was increased 
by the application of irrigation water. 
Water increased the nitrifying powers of all the soils except the oat 
soil. 
There was a difference of 2 degrees Fahrenheit in the temperature of 
the soil of irrigated and unirrigated in favor of the unirrigated. This 
difference in temperature was perceptible to a depth of 4 feet. 
The number of organisms was higher in the cropped than in the fallow 
plots, and this is probably due to the plant residues left upon the cropped 
soil. 
Naming the soils in the order of increasing ammonifying powers, we 
have alfalfa, oats, com, potato, and fallow. By naming them in the 
order of increasing nitrifying powers, they are fallow, corn, oats, alfalfa, 
and potato. 
The alfalfa not only feeds closer upon the nitric nitrogen of the soil 
than do other crops but it also increases the nitrifying powers of the soil. 
Hence, it would deplete the soil of its nitrogen more rapidly where the 
entire crop is removed than would other crops. 
The use of irrigation water increases the bacterial activities of the soil, 
which render soluble the nitrogen, and where excessive quantities of 
water are used considerable of this is washed from the soil, thus unneces¬ 
sarily depleting the soil of its nitrogen. This in turn gives diminished 
yields on the soil. 
LITERATURE CITED 
(1) Andr£, Gustave. 
1902. Sur la nature des composes azotds qui existent dans le sol & diff£rentes 
hauteurs. In Compt. Rend. Acad. Sci. [Paris], t. 135, no. 26, p. 
1353 - 1357 - 
(2) - 
1903. Sur les composes azotes qui contient la terre arable. In Compt. Rend. 
Acad. Sci. [Paris], t. 125, no. 13, p. 820-822. 
(3) Brown, P. E. 
-1912. Bacteriological studies of field soils. II. The effects of continuous 
cropping and various rotations. In Centbl. Bakt. [etc.], Abt. 2, Bd. 
35, No. 11/13, p. 248-272. 
82983°—17-5 
