1919] 



Pendleton: A Study of Soil Types 



421 



less (even to denitrification) absolutely and relatively as compared 

 with the surface horizons, than the amount fixed by the P> and C 

 horizons of the soils nos. 20 to 25 inclusive. 



Comparing' the nitrogen fixation of the various types, there seeii) 

 to be no characteristic differences between the heavy Altamonl and 

 Diablo typos, while the lighter Hanford and San Joaquin types arc 

 considerably different from each other. As a whole there is bu1 a fair 

 degree of similarity between the samples of a given type. The degree 

 of variation within types is large. 



Table 33 — Nitrogen Fixation 

 Diablo Clay Adobe 



Milligrams X per gram of mannite 



A 



B 



Increase Increase Increase 



Checks over Checks over Clucks over 



Sample Cultures average checks Cultures average checks Cultures average checks 



Table 34 — Nitrogen Fixation 



Altamont Clay Loam 



Milligrams N fixed per gram of mannite 



A 



B 



[ncn Increase Inci 



Checks over Chocks over Checks over 



Sample Cultures average checks Cultures average checks Cultures average ehe.-ks 



