Dec. 4, 1916 
Nitrification in Semiarid Soils 
435 
present in low concentrations. It is recognized that different organic 
fertilizers undergo biochemical decomposition in varying degrees in a 
given soil, and this for a number of reasons, some of which will be dis¬ 
cussed in a later paper. The writer holds, however, that the methods 
now employed by many students of nitrification, in which high con¬ 
centrations of nitrogenous materials are added and the nitrate determined 
at a fixed interval of time, are not only unsatisfactory but that the re¬ 
sults thus obtained are likely to be more misleading than informing. 
In the light of the results obtained in this investigation, it seems highly 
probable that at least some of the peculiarities that have been noted in 
previous nitrification studies will be found to disappear under the more 
rational procedure of studying the activities of the organisms in an 
environment as nearly similar to that of the field as possible. The writer, 
while criticizing the methods in common use, freely admits that some of 
the conclusions previously drawn by him from studies with Hawaiian 
soils are open to serious question because of the methods employed (14). 
The nitrate merely represents one of the end products formed; and in 
the case of an organic substance the intermediate products that are pro¬ 
duced may, either directly or indirectly through the effect upon other 
organisms, exert much influence upon the oxidation of ammonia. In 
the presence of large amounts of materials it is highly probable that the 
relations of the different groups of organisms present become greatly 
changed, with a consequent effect on the oxidizing activity of the nitri¬ 
fying organisms. 
It is, of course, a matter of scientific interest that certain soils are 
capable of supporting active nitrification of 1 per cent of dried blood, 
while others are not, and the reasons underlying these differences are 
matters deserving further study, but so far as the practical side of 
nitrification is concerned the writer holds that laboratory experiments 
should be conducted under conditions as nearly comparable with those 
that obtain in the field as possible, and that at the present time nothing 
more than scientific interest can safely be attached to the results obtained 
with the use of such abnormally high concentrations of nitrogenous 
materials as are commonly used in laboratory experiments on this subject. 
Many American bacteriologists have apparently accepted the conclu¬ 
sions of Stevens and Withers (29, 30) and have multiplied laboratory 
tests in a conventional way without seriously questioning the method. 
The result has been that the practical aspects of nitrification studies have 
become extremely empirical. While it has frequently been stated that 
nitrification in the laboratory is not strictly comparable with that in 
the field, the conditions obtaining in the nitrification of 1 per cent dried 
blood in the laboratory have been referred to as optimum conditions 
(27). The preceding data indicate, however, that such may be far from 
the case. The writer thoroughly agrees with the position taken by 
Lohnis and Green (25) and Allen and Bonazzi (2) in their recent discus¬ 
sions of this subject. 
