72 
Journal of Agricultural Research 
Vol. VII, No. a 
In addition to these observations, it may be remarked that in the last 
column, in the foreign soils, dried blood stands first, as it does in the Bay 
and Ukiah areas, and soil nitrogen stands third. Sulphate of ammonia 
in the foreign soils again takes last place instead of a close second, as in 
the Riverside and Pasadena areas, afid cottonseed meal stands second 
instead of first. 
COMPARISON OF FOREIGN AND CALIFORNIA SOILS 
It has been shown that 52 per cent of the foreign soils, which include 
several arid or semiarid soils, produce more than 15 mgm. of nitrate nitro¬ 
gen out of the total soil nitrogen present. Neither the Bay nor the Ukiah 
areas includes any soil of such nitrifying activity. However, it was not 
expected that they would produce the same number of milligrams 
of nitrate nitrogen, but merely an amount having an approximately 
similar ratio to the total nitrogen as that in the foreign soils. While 
the Riverside and the Pasadena areas, with 24 per cent and 18 
per cent, respectively, of soils with an equivalent nitrifying power to 
that of the foreign soils mentioned, are much more active than those of 
the other two arid-soil areas just referred to, their records are still far 
behind those of the foreign soils. These comparative data were arranged 
as noted on the basis of equivalent quantities of total nitrogen, a basis 
employed because of the claim which has been made that the quantity 
of nitrogen rendered available in a soil is always a certain constant pro¬ 
portion of the total nitrogen present in soils. If the latter theory is 
tenable, arid soils are certainly very much more feeble in the nitrification 
of soil nitrogen than humid soils. But if the theory above mentioned 
is incorrect, the data are all the more emphatic as to the considerable 
disparity (in favor of the humid soils) between the nitrifying power for 
soil nitrogen of soils of the arid and humid regions. 
On the assumption that the stimulating or depressing effect of a certain 
nitrogenous material on the soil's nitrifying power under laboratory con¬ 
ditions is a justifidble criterion, the percentage of soils in every group 
which produced less or more nitrate from soil plus fertilizer nitrogen than 
from soil nitrogen alone have been noted. Table IX has been arranged 
on the basis of all those calculations. 
Table IX. —Percentage of soils in every area which produced less nitrate with fertilizer 
plus soil nitrogen than from soil nitrogen alone 
Source of nitrogen. 
Soil. 
Sulphate of 
ammonia 
and soil. 
Dried blood 
and soil. 
Cottonseed 
meal and 
soil. 
Foreign. 
Ukiah... 
88 
28 
20 
35 
46 
40 
Bay.. 
l6 
43 
26 
Pasadena.. 
21 
63 
21 
Riverside. 
II 
50 
II 
