202 
Journal of Agricultural Research 
Vol. IX, No. 7 
At the time the samples were taken the ammonia in the eight soils 
varied from 0.32 mgm. in soil C to 0.88 mgm. in soil S. There was little 
change in the ammonia content of the control samples at any time during 
the incubation period of 90 days, whether the samples were held in the 
incubator at 28° C. or in the field at 17 0 to 20°. 
The nitric nitrogen in the soils at the time the samples were taken 
varied from 0.18 mgm. in soils B and T to 0.57 mgm. in soil F. After 
14 days’ incubation at 28°, the control samples showed an appreciable 
increase in nitrates. From 14 to 28 days there appears to have been 
little additional increase in soils B, T, C, E, and U. On comparing the 
nitrates in the control samples after 28 days’ incubation in the two series, 
it appears that the increase in nitrates is about the same, regardless of 
the temperature at which the soils were held. From 28 to 56 days there 
is a rather marked increase in nitrates in the control samples in the 
incubator and also in the field. From 56 to 90 days there was a still 
further increase in nitrates in most instances; and on comparing the 
nitrates found in the samples held in the incubator and samples held in 
the field, it appears that the difference in temperature has had little 
effect on tht increase in nitrates in these soils. 
When 0.1 per cent of dried blood was added, there was an increase in 
the ammonia after 14 days in all of the soils except O and E. After 28 
days’ incubation the soils receiving 0.1 per cent of dried blood contained 
only a little more ammonia than the control samples. It would seem 
that the difference in temperature had little or no effect on the accumu¬ 
lation of ammonia in the soils at any time during the incubation period of 
56 days, when o. 1 per cent of dried blood was added. There was a marked 
increase in nitrates in all of the soils receiving 0.1 per cent of dried blood 
after 14 days’ incubation at 28°. On comparing the amount of nitrates 
found in the soils held at 28° and those held at from 17 0 to 20°, it is seen 
that the amount of nitrates produced from 0.1 per cent of dried blood is 
quite uniform in all of the soils, and it would seem that the difference in 
temperature has not been an influential factor in determining the rate 
of nitrification. 
The addition of 1 per cent of dried blood caused a very large increase in 
ammonia. After 14 days’ incubation at 28°, the ammonia varied from 
56.28 mgm. in soil U to 89.04 mgm. in soil T. From 14 to 28 days there 
appears to have been a slight reduction in the ammonia content of some 
of the soils, although it is still extremely high in all cases. On comparing 
the amount of ammonia found in the soils held in the incubator and those 
held in the field soils, it would seem that the soils held in the incubator 
contained somewhat more ammonia. After 56 days the ammonia is still 
high in all of the soils, whether held in the incubator or in the field, thus 
indicating that nitrification has been very incomplete, even after 56 days’ 
incubation. 
The increase in nitrates from the addition of 1 per cent of dried blood 
after 14 days’ incubation varies from o in soils B and C to 26.11 mgm. in 
