192 
Journal of Agricultural Research 
Vol. IX, No. 7 
red clover began during the first seven days and continued to increase 
rather uniformly throughout the experiment. At the conclusion of the 
experiment, from 34.88 to 57.2 per cent of the nitrogen added was re¬ 
covered as nitrates. The increase in total nitrogen in the soils receiving 
red clover varied from 24.56 per cent in the virgin soil to 52.96 per cent 
in the productive soil. 
The addition of 1 per cent of alfalfa caused considerable increase in 
the ammonia content of the productive and unproductive soils during 
the first seven days, but a slight reduction in the virgin soil. During 
the latter part of the incubation period the increase in ammonia in these 
soils is very small, and the percentage of nitrogen recovered as ammonia 
at the conclusion of the experiment varied from nothing in the virgin 
soil to 2.94 in the unproductive soil. Considerable increase in nitric 
nitrogen took place during the first seven days in the productive and 
unproductive soils, but very little increase in the virgin soil. The nitric 
nitrogen continued to increase throughout the incubation period, and at 
the end of the six weeks the percentage of nitrogen recovered as nitrates 
from alfalfa varied from 47.97 in the virgin soil to 65.59 in the unpro¬ 
ductive soil. There was a gain in total nitrogen in each of the soils to 
which alfalfa was added. 
When these soils were incubated without the addition of nitrogenous 
materials, the ammonia content remained quite uniform throughout the 
incubation period; but there was an appreciable increase in nitrates, 
which seemed to have reached a maximum after 21 days in the pro¬ 
ductive and virgin soil and after 35 days in the unproductive soil. 
On July 16, soil samples were secured from four plots in the experi¬ 
mental field at the Citrus Experiment Station, Riverside, Cal., and one 
sample from an adjacent virgin soil. Each of these soils was divided 
into four portions of 1 kgm. each, one portion from each soil receiving 1 
per cent of dried blood. Each of the other portions received 2 per cent 
of red clover, alfalfa, or buckwheat. The results obtained in this experi¬ 
ment are presented in Table V. 
When 1 per cent of dried blood was added to these soils, there was a 
considerable increase in the ammonia content of each of the five soils 
included in the experiment. The percentage of nitrogen recovered as 
ammonia at the end of six weeks varied from 18.25 * n soil U to 38.37 in 
the virgin soil. The increase in nitric nitrogen in these soils is extremely 
variable. In the virgin soil and soil B only 1.22 per cent of the nitrogen 
added in dried blood was recovered as nitrates, while in soils P and U 
32.65 and 36 per cent, respectively, were recovered. The percentage of 
nitrogen lost varied from 13.05 in plot F to 47.96 in plot B. 
When 2 per cent of red clover was added, there was an appreciable 
increase in the ammonia content of all of the soils. However, the average 
percentage of nitrogen recovered as ammonia is only 4.5. The lowest 
increase in nitrates is in the virgin soil and amounts to 26.51 per cent 
