434 
Journal of Agricultural Research 
Vol. VII, No. 10 
of nitrate formed and the percentage of the nitrogen added that was 
nitrified. 
When i per cent of dried blood was used, the nitrifying activity was 
found to be feeble or even negative in certain soils in which i per cent of 
bone meal and 0.2 to 0.3 per cent of ammonium sulphate underwent 
active nitrification, as was previously found by Lipman and Burgess 
(24). However, when low concentrations of dried blood were employed, 
such as are used in the field, active nitrification took place in every case; 
and when equal amounts of actual nitrogen were added, it was found 
that the yields of nitrate were quite similar, whether the nitrate had been 
derived from dried blood, bone meal, or ammonium sulphate. High 
concentrations of bone meal with a nitrogen content corresponding to 
that furnished by 1 per cent of dried blood were also toxic to nitrifica¬ 
tion, very much as was the case with 1 per cent of dried blood. 
Experiments were made with widely different types of soil from a 
number of localities in southern California. It was found that the 
inability to nitrify 1 per cent of dried blood is not confined to any one 
type of soil nor to soils low in organic matter. The results as a whole 
seem to warrant the conclusion, however, that the soils of southern 
California in general are capable of supporting active nitrification of 
dried blood, provided it be added in concentrations corresponding to 
field practice. 
It w T as found that the effects produced by the addition of alkali salts 
varied greatly when different concentrations of nitrogenous materials 
were employed. In a given soil a concentration of 0.05 per cent of 
sodium carbonate was distinctly toxic to the nitrification of 1 per cent 
of dried blood, while as high a concentration as 0.4 per cent produced 
no effects on the nitrification of 0.1 per cent of dried blood. Likewise, 
0.1 per cent of sodium carbonate was toxic to the nitrification of 0.15 
per cent of ammonium sulphate, and markedly stimulating when 0.0625 
per cent of ammonium sulphate was used. Similar statements may be 
made with regard to the effects of sodium sulphate. 
The results also show that widely different conclusions may be drawn 
from laboratory experiments when different periods of incubation are used. 
Nitrites were found to accumulate in large amounts where excessive 
amounts of nitrogenous materials were employed. In some cases 
the nitrite content greatly exceeded the nitrate content after an in¬ 
cubation period of several weeks. Likewise, the addition of alkali salts 
may suppress nitrate formation, while at the same time permitting nitrite 
formation to proceed actively. 
It is necessary to make allowance for the nitrite present in the de¬ 
termination of nitrate by the aluminum reduction or phenol-disulphonic- 
acid methods, but the error introduced by nitrite is far greater with the 
former method than with the latter. 
It is not intended to give the impression from the above that all 
nitrogenous materials will undergo nitrification at equal rates when 
