66 
Journal of Agricultural Research 
Vol. VII, No. a 
nitrate, and 23 soils, or about 43 per cent of the whole number in this 
area, which nitrify 10 per cent or more of the nitrogen present. When 
compared with 66 per cent of the soils with such a record among the 
foreign group with the soil nitrogen alone, it still seems clear that the arid 
soils are inferior as nitrifying media. Nevertheless one remarkable figure 
must not be lost sight of among the relative data of Table V, Group II— 
that is, the 94 per cent transformation of the totai nitrogen present 
into nitrate by the Tejunga fine sand. This means an almost complete 
nitrification of both soil nitrogen and sulphate of ammonia nitrogen 
added in one month under the conditions noted. 
In the case of dried-blood nitrogen, the Riverside area soils again 
behave typically. Fifty per cent of all the soils produce in the abso¬ 
lute, as reference to Table V, Groups III and IV, will show, less nitrate 
from dried blood plus soil nitrogen than from the latter alone. In the 
Riverside area, however, even more markedly than in the two preceding 
California areas, there is a considerable number of soils producing large 
quantities of nitrates from soil plus dried-blood nitrogen. Two points 
of difference are noted between the Riverside area soils on the one 
hand and the two groups just mentioned on the other. There are 
more soils of the class just described in the Riverside area soils than in 
the Bay area or Pasadena area soils, and very few of them contain 
nearly as much as 0.1 per cent of total nitrogen. Besides, the absolute 
quantities of nitrate produced are in four or five cases exceptionally 
high. It must be noted, however, that in only one case does the nitrifi¬ 
cation of dried blood exceed that of the soil nitrogen when the soil is 
stony, sandy, or gravelly and contains little loam or clay. Even that 
one exception shows but feeble powers of nitrification. In the other 
cases the soils vary from fine sandy loams with large internal surface 
to clay loams and clays with larger internal surface. Likewise, it will 
be noted that in the cases of the 3 soils with more than 0.1 per cent 
total nitrogen every one made a very good showing in the nitrification 
of dried-blood nitrogen. It will further be observed that of the 12 soils 
producing more than 25 mgm. of nitrate nitrogen in this series only one 
contained less than 0.04 per cent of total nitrogen. 
On the relative basis it follows that the Riverside area soils must 
surpass the Bay area soils in efficiency in the dried-blood series and that 
they must equal the Pasadena area soils, but they do not do either with 
respect to the foreign soils. For example, five soils in the group now 
under consideration transform more than 20 per cent of the blood plus 
soil nitrogen into nitrate, and six more transform more than 15 per 
cent of the total nitrogen present in that manner. This is a record only 
slightly behind that of the Pasadena area soils, but as far behind that of 
the foreign soils as it is ahead of the Bay area soils. So far as maximum 
transformation is concerned, however, the Tejunga fine sandy loam in 
the Riverside area surpasses any soil in the Pasadena area by nitrifying 
