3i8 
Journal of Agricultural Research 
Vol. IX, No. 9 
The quantity of nitric nitrogen found in the alfalfa and oat soil is low 
during the spring and it is quite evenly distributed throughout the 6 
feet, while the com, potato, and fallow soil is exceptionally high in nitric 
nitrogen in the first foot. The total quantity of nitric nitrogen in the 
potato and fallow soil throughout the season is higher than in the other 
plots, but in the case of the fallow there is a marked decrease in the total 
nitric nitrogen of the soil. This must be due to the action of bacteria 
in transforming the nitrates into protein material within the soil, because 
it is not likely that this quantity of water would be sufficient to carry 
the nitric nitrogen beyond the 6 feet. Furthermore, if we compare the 
nitrates found in the soil for the last three years with those for the 
previous eight years, we find that during the last three years the total 
quantity of nitric nitrogen in the 6 feet of soil is one-third lower than 
it was during the first period, showing a decrease in the nitric nitrogen 
of fallow soil. Whether this can be due to a decrease in the total nitrogen 
of the soil or merely to a decrease in the nitrifying powers of the soil 
can not be answered with the data at hand. There is the possibility 
that in the presence of large quantities of nitrates there may be developed 
a strain of bacteria which would rapidly transform the ammonia and 
nitrates into protein material. It does not seem possible that any great 
quantity of the nitrogen could have disappeared through denitrification, 
for the soil is well aerated and the quantity of organic matter present 
is extremely low. 
PILOTS RECEIVING NO IRRIGATION WATER 
All of the plots in this series were treated as nearly uniform as pos¬ 
sible. The oats and alfalfa plots were not cultivated. The plots were 
unirrigated, and the marked difference in the nitric nitrogen of the various 
plots is probably due to the crop factor. The average summarized 
results for the three years are given in Table XVIII. 
The nitric nitrogen of all the unirrigated plots is comparatively high 
in the spring, decreases in the summer, and increases in the fall. The 
greatest decrease occurs in those plots having the greatest accumulation 
of nitrates. In the potato plots the unaccounted-for nitrates amount 
to 82.6 pounds per acre, only slightly greater than in the fallow, which 
shows a loss of 71.2 pounds. The fact that this loss is so pronounced in 
the fallow soil shows that it is not due to the removal of the nitric nitro¬ 
gen by the growing plants. The fact that it is so rapidly regained dur¬ 
ing the winter months clearly indicates that it is not due to water remov¬ 
ing the soluble nitrates; nor is it due to denitrification, for these plots 
are as high in total nitrogen as are others which have not shown this 
seasonal loss of nitrates. The probable explanation of the phenomena 
which we have so continuously observed in these plots is the following. 
The accumulation of large quantities of nitrates in the soil depresses to 
a degree the speed with which the nitrifying organisms act, but it increases 
