426 
Journal of Agricultural Research 
Vol. VII, No. 10 
fication. The results show, furthermore, that 1 per cent of dried blood 
may be an excessive concentration, even in a highly organic soil; less 
nitrate was formed in the samples for each foot where 1 per cent of 
dried blood had been added than in the control portions. 
A concentration of 0.1 per cent of dried blood, or an equivalent amount 
of nitrogen in the form of ammonium sulphate, underwent vigorous and 
practically equal nitrification in the soil from the first foot and was also 
actively nitrified in the subsoils from the second and third feet. Am¬ 
monium sulphate likewise underwent considerable nitrification in the 
samples from the fourth and fifth feet; but the amounts of nitrate pro¬ 
duced with a 0.1 per cent concentration of dried blood in soil from these 
depths were approximately the same as in the checks, indicating that a 
concentration of o. 1 per cent of dried blood may be excessive. 
Considering the fact that nitrification took place in the check portions 
and where ammonium sulphate was added, the conclusion seems war¬ 
ranted that the subsoil from this orchard at least possesses the potential 
capacity of producing nitrates down to a depth of 5 feet. 
However, the writer does not consider it safe to conclude from the 
preceding data that active nitrification takes place in the field in the 
subsoils of the orchard from which the above sample was drawn, since 
much more thorough aeration took place after the samples were drawn 
than ordinarily takes place in the subsoil in situ. 
The results, as a whole, again emphasize the importance of employing 
low concentrations of nitrogenous materials and show that the inability 
to nitrify a concentration of 1 per cent of dried blood is not confined to 
humus-poor soil, as suggested by Lipman and Burgess (24). 
EFFECTS OF ALKALI SALTS ON NITRIFICATION AS MODIFIED BY THE 
CONCENTRATION OF NITROGENOUS MATERIALS 
One of the most important soil questions in the semiarid region relates 
to the effects of alkali salts, particularly the carbonate, chlorid, and 
sulphate of sodium. As already stated, Lipman and his coworkers (17, 
18, 19, 22) have devoted considerable study to the biochemical effects 
of these salts. But the conclusions which were drawn relative to nitri¬ 
fication were based on the effects produced with a concentration of 1 or 
2 per cent of dried blood. In the light of the results presented above, 
it becomes a matter of interest to study the effects of alkali salts with 
the use of varying concentrations of nitrogenous materials. 
The soils used were drawn from the check and manured plots; the 
required amounts of the salts were added in solution after the dried 
blood or ammonium sulphate had previously been mixed with the soil. 
The same percentage of moisture and an incubation period of four weeks 
were employed, as in the previous series. Table V gives the results of 
this series. 
