6 o 
Journal of Agricultural Research 
Vol. VII, No. a 
Pasadena area falls short, approximately by 21 per cent, of having as 
large a number of soils with more than 0.1 per cent of nitrogen as the 
foreign-soil group. While, therefore, the soils of the Pasadena area 
approach more closely in nitrogen content those of the foreign group 
than do the soils of the Bay area, they are still distinctly inferior to the 
foreign soils. The effect of aridity of climate therefore makes itself 
plainly manifest in the Pasadena as it does in the Bay area series. It 
must be further remarked, however, that again owing to climatic con¬ 
ditions, a larger number of soils with less than 0.05 per cent of nitrogen 
are found in the Pasadena area than in the Bay area, and more of that 
class than among the foreign soils. The percentage of such is greater 
than 21 in the Pasadena area, as against 16 for the Bay area, and 14 for 
the foreign soils. Two soils out of the thirty-three in the Pasadena area 
contain less than 0.02 per cent of nitrogen, and two others contain less 
than 0.03 per cent of nitrogen. 
On the basis of the absolute values for the nitrate from the soil nitro¬ 
gen (Table IV, Group I) it would seem that the Pasadena area soils, 
though manifestly superior in nitrifying power as a class to the Bay area 
soils, are still far from being equal in that direction to the foreign soils. 
Thus, for example, 85 per cent of the soils in the Pasadena area produced 
less than 10 mgm. of nitrate nitrogen in 100 gm. of soil under the cir¬ 
cumstances described, while the foreign soils numbered only 27 per cent 
of such soils among them, it is therefore very clear that so far as abso¬ 
lute quantities of nitrate produced are concerned even the fertile Pasa¬ 
dena area soils are inferior transformers when compared with foreign 
soils. On the other hand, when compared with the Bay area soils on the 
basis of a 5-mgm. production of nitrate, the Pasadena soils are clearly 
superior. Thus, among the latter there are 20 soils of the class last 
mentioned, whereas among the Bay area there is but 1 such soil. 
On the relative basis, or that the criterion of which is percentage of 
soil nitrogen transformed into nitrate, the Pasadena area soils make 
even a better showing than on the absolute basis when compared with 
the Bay area soils. Likewise, they are less inferior when so judged in 
comparison with the foreign soils for obvious reasons concerned with 
the total nitrogen content. Thus 4 soils out of 33 (12 per cent) in the 
Pasadena area transforms more than 20 per cent of their total nitro¬ 
gen content into nitrate as against 11 out of 44 soils of that class, or 
25 per cent, in the case of the foreign soils. The highest individual 
record for percentage nitrogen transformation is attained equally by 
the Zelzah light loam and the Holland loam, which transform more than 
26 per cent of the total nitrogen present into nitrate. This, while very 
high, is below the record attained by several of the foreign soils. All 
of these considerations, moreover, must be viewed in conjunction with 
the fact that even the group of foreign soils contains a few arid or semi- 
arid soils similar to the California soils which are being studied here. 
