196 
Journal of Agricultural Research 
Vol. IX, No. 7 
It is seen that the addition of 1 per cent of dried blood caused a large 
increase in the ammonia content of soils H, B, and virgin, a smaller 
increase in soil F, and a comparatively small increase in soil U. The 
percentage of nitrogen recovered as ammonia from the dried blood varies 
from 4.69 in soil U to 34.79 in soil B. There was no increase in nitric 
nitrogen in the virgin soil at any time during the incubation period of 
six weeks. On the other hand, the results indicate that there was a 
slight reduction of nitrates as compared with the amount found in the 
control. The increase in nitric nitrogen in soils H and B is very little; 
but in soils F and U there is a decided increase after the first 14 days, 
and the increase continues throughout the incubation period. In soil 
U 51.43 per cent of the nitrogen added in dried blood was recovered as 
nitrates after six weeks' incubation. In soils H, B, and virgin none of 
the nitrogen added as dried blood was recovered as nitrates. The loss 
of nitrogen from the addition of 1 per cent of dried blood varies from 
13.27 per cent in soil U to 58.16 per cent in soil H. 
The addition of 2 per cent of vetch caused an increase in the ammonia 
content of all of the soils, but the amount of increase is small as com¬ 
pared with the increase from dried blood. At the conclusion of the 
experiment the percentage of nitrogen recovered as ammonia varied 
from 2.58 in soil U to 20.83 i n soil B. After 14 days there was an increase 
in nitrates in all of the soils to which vetch had been added, but the 
increase in the virgin soil and soil B were very small, and during the latter 
part of the incubation period the virgin soil, to which 2 per cent of vetch 
had been added, contained less nitric nitrogen than the control. In soil 
U 40.37 per cent of the nitrogen added in vetch was recovered as nitrates 
after six weeks' incubation, the virgin being the only soil in the series 
which failed to give less than 17.61 per cent of nitrogen as nitrates. 
Soil H and the virgin soil show a slight loss of total nitrogen, while soils 
F, B, and U show slight gains, varying from 9.51 to 18.1 per cent of the 
nitrogen added. 
The addition of melilotus caused only a small increase in the ammonia 
in soils U and F, but considerable increases in soils H and B and the 
virgin soil. At the conclusion of the experiment the ammonia recovered 
from melilotus varied from 1.45 per cent in soil H to 23.97 P er cent in 
the virgin soil. After 14 days' incubation soils U and F showed a marked 
increase in nitrates, soils H and B comparatively small increases, while 
the virgin soil showed no increase. There are gains in nitrates in all of 
the soils of from 14 to 42 days, and at the conclusion of the experiment the 
percentage of nitrogen recovered as nitrates from melilotus varies from 
27.19 in the virgin soil to 84.46 in soil F. There is a decided increase in 
the total nitrogen in all of the soils receiving melilotus. In soil F the 
increase amounts to more than the nitrogen added in melilotus. 
Soybeans, unlike vetch or melilotus, caused very little or no increase 
in the ammonia content of the soils. The increase in nitrates is also 
