Oct. 9, 1916 
Nitrifying Powers of Humid and Arid Soils 
61 
Some very interesting data are available in Table IV, Group II, which 
gives the results with sulphate of ammonia. Thus, only about 21 per cent 
of the soils in the Pasadena area produced less nitrate from the sulphate 
of ammonia nitrogen plus the soil nitrogen than from the latter alone. 
It is interesting to note that the percentage of such soils is so nearly 
the same in the two arid-soil series thus far considered, even though 
the latter are in other respects very different. To emphasize again the 
wide difference existing in respect to the sulphate-of-ammonia nitrogen 
between the humid (as illustrated by the foreign) and the arid soils, 
one need but recall that 88 per cent of the humid soils failed to respond 
to sulphate of ammonia, whereas only 20 per cent of the arid soils 
behaved in that manner. 
As other points of interest in Table IV, Group II, may be mentioned 
the following: (1) Only four soils in the whole series transform less than 
5 per cent of the total nitrogen present into nitrates. (2) Six soils of 
the series transform more than 20 per cent of the total nitrogen present 
into nitrates. (3) In one soil, the Dublin clay, over 37 per cent of 
the total nitrogen present is nitrified, and another soil, the Hanford fine 
sandy loam, approaches closely to that record. (4) Both soils, the 
Zelzah light loam and the Holland loam, which have the highest record 
on the relative basis in Table IV, Group I (soil nitrogen alone), lose in 
nitrifying power very markedly when sulphate of ammonia is added to 
them, while the Dublin clay and the Hanford fine sandy loam, which do 
only moderately well with soil nitrogen alone, make the highest records, 
as above indicated, with soil nitrogen plus sulphate-of-ammonia nitrogen. 
(5) It should be noted that in the sulphate-of-ammonia series no soil 
loses its original nitrate content without replacing and adding to it by 
nitrification. A loss of the soil's original nitrate content does, however, 
occur in the case of two soils, the Chino loam and the Yolo loam, in the 
series with soil nitrogen alone. All of these points, moreover, are of great 
interest in comparison with the results for the Bay area soil series as 
obtained by the use of sulphate of ammonia. In general, of course, the 
superiority at nitrification of the soils in the Pasadena series to that of 
the Bay area series is more emphasized in Table IV, Group II, than here¬ 
tofore. 
In the experiments with dried blood in the case of the Pasadena area 
soils (see Table IV, Group III), results totally different in nature from 
those obtained with sulphate of ammonia are noted. Thus, 63 per cent 
of all the soils tested produce less nitrate under the circumstances above 
described when dried blood plus the soil nitrogen are available for nitri¬ 
fication than when only the soil nitrogen.is present. This is 20 per cqnt 
in excess of the number of such soils in the Bay area, despite the fact 
that the latter area contains less soils than the Pasadena area with a 
percentage of nitrogen higher than 0.1. Again, however, as in the case 
of the Bay area, several of the soils produce in absolute quantities much 
55856 °— 16——2 
