Oct. 9, 1916 
Nitrifying Powers of Humid and Arid Soils 
55 
Table; II .—Total nitrogen present transformed into nitrate in foreign soils 
Nitrifiable material. 
Soils transform¬ 
ing zo per cent 
or more of total 
nitrogen into 
nitrate. 
Soil nitrogen alone.. 
Per cent. 
68 
23 
47 
45 
Soil nitrogen plus ammonium sulphate.... 
Soil nitrogen plus dried blood. 
Soil nitrogen plus cottonseed meal..... 
Based on the absolute criterion of the production of 20 mgm. of nitrate 
nitrogen, or more, under the circumstances noted, sulphate of ammonia 
still remains the lowest in the scale with only 8 soils possessing such a 
record, the soil nitrogen is next with 9 soils in that class, cottonseed-meal 
nitrogen is next with 13 such soils, and dried-blood nitrogen stands best, 
with 31 such soils. The corresponding figures obtained when the pro¬ 
duction of 15 mgm. of nitrate is taken as a criterion are as follows: Soil 
nitrogen, 23 soils; ammonium-sulphate nitrogen, 11 soils; dried-blood 
nitrogen, 36 soils; and cottonseed-meal nitrogen, 28 soils. 
In brief, therefore, dried-blood nitrogen takes first place for the abso¬ 
lute amount of nitrate produced therefrom by the foreign soils, cotton¬ 
seed-meal nitrogen being second, soil nitrogen third, and ammonium- 
sulphate nitrogen last. On the relative basis, however, the dried-blood 
nitrogen goes from first to second place, and the soil nitrogen from 
third to first place, with the sulphate of ammonia remaining last, and 
the cottonseed meal third in order. 
EXPERIMENTS WITH CALIFORNIA SOILS 
In order to make the choice of California soils representative not only 
of the arid region but also of parts of the State with widely varying 
climatic and other conditions, soil types were chosen from two central to 
northwest soil-survey areas and from two southern California areas. 
These areas were the Ukiah and the Bay areas and the Riverside and 
the Pasadena areas. The rainfall for the first two areas varies from 20 
to 40 inches or more a year, depending oil the location; and nearly all 
of it falls during the winter. The precipitation for the Riverside and 
Pasadena areas varies from 7 to 12 inches or more, also limited almost 
entirely to the winter months. The nitrification tests were arranged as 
described above and in the same way as those of the foreign soils. The 
first area to be considered here is the Bay area, and Table III sets forth 
the results obtained with the soil types of that area and with the different 
forms of nitrogen. 
