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University of California Publications in Agricultural Sciences [Vol.3 



NITRIFICATION29 



The most noticeable thing about the nitrification results is the 

 very wide range of variation in the various representatives of the 

 Hanford fine sandy loam as compared with the quite uniform and 

 consistent results obtained with the other types. 



Diablo clay adobe. — The percentage of nitrogen nitrified (table 

 37, 38, and fig. 23) is uniformly low. The B samples showed a less 

 vigorous nitrifying flora (except in the case of no. 6) than the sur- 

 face ones. Dried blood in the quantities used seems to depress the 





A S. N. + Cottonseed Meal 

 A S. N.+ (NH0*SO4 



A S. N.+ Dried Blood 

 A Soil Nitrogen 



1 2 5 6 Soils 



Percentages of N. Nitrified 



Fig. 23. Graph showing the percentages of nitrogen in various nitrogen 

 containing materials nitrified in the four samples of the Diablo clay adobe. 



normal activity (A horizon average 0.81%), while the (NH 4 ) 2 S0 4 

 (A horizon average 3.03%) and the cottonseed meal (A horizon 

 average 2.91%), as compared with the incubated control tend to in- 

 crease the percentage of nitrogen nitrified. It should be kept in mind 

 that an absolute increase in the nitrogen content may accompany a 

 decrease in the percentage, due to the greatly increased amount of 

 nitrogen present after the addition of a nitrogenous substance. The 

 variation of the samples within this type is very moderate as compared 

 with the San Joaquin and Hanford types. 



29 The figures used in the discussion shows the percentages of the nitrogen in 

 the cultures which were nitrified. There are two tables for the samples of each 

 type. The percentages of nitrogen nitrified are rearranged in a second table for 

 greater ease in comparing results. 



