422 
Journal of Agricultural Research 
Vol. VII, No. 10 
that from the control plot. It is not deemed necessary to dwell further 
on the ammonification of organic materials in these soils. Suffice it to 
say that the ammonia has been determined in a large number of instances 
throughout this work and without exception ammonification has been 
found to be active in every soil studied. The above data on ammonifi¬ 
cation are submitted merely to show that nitrification was not limited 
by inactive ammonification and not as a special contribution to the 
study of ammonification. 
Considering the amounts of nitric nitrogen found, it will be noted 
that little or no nitrification took place except in the soil previously 
treated with manure. In this case quite active nitrification took place* 
It is of special interest that only the most enfeebled nitrification of dried 
blood took place in the virgin soil; and although slightly more nitrate 
was formed in the virgin soil than in the check plot, the difference is too 
small to be noteworthy. 
Two of the plots (C and S) in the field experiments from which the 
above samples were drawn have been annually fertilized with dried blood 
for the past nine years (1907-1915). During the past two years (1914- 
15) the application has been made at the rate of 1,080 pounds per acre. 
Notable stimulation in the growth and yield of fruit has been produced. 
One of these plots (C) lies adjacent to the check plot used in the foregoing 
experiments. Soil samples drawn at frequent intervals during the past 
two years from this and other plots fertilized with dried blood have 
consistently shown a well-defined increase in nitric nitrogen over that in 
the unfertilized plots. Furthermore, considerable increases in the 
nitrate content have been found following each application of dried blood. 
It would seem, therefore, that dried blood undergoes active nitrification 
in the field where no other form of organic matter has been applied, 
notwithstanding the fact that the above data indicate that both the virgin 
soil and control plot are unable to nitrify dried blood. 
Two questions presented themselves: First, why does dried blood 
undergo active nitrification in the field but not in the laboratory? 
Second, why is it that dried blood undergoes active nitrification in the 
soil from the manured plot but apparently not in the control plot? 
Considerations arising out of these questions have led to an extended 
study of the factors affecting nitrification in the field and laboratory. 
NITRIFICATION AS AFFECTED BY VARYING CONCENTRATIONS OF 
MATERIALS 
As stated above, 1,080 pounds of dried blood per acre have been ap¬ 
plied annually for the past two years (1914-15) to plots C and S. Until 
the present year (1916) only one-third of this quantity was applied at 
one time, the remaining two-thirds being applied at intervals of about 
two months each. But assuming that the entire amount becomes thor¬ 
oughly mixed with the soil to a depth of 6 inches and estimating that the 
