470 University of California Publications in Agricultural Sciences [Vol. 3 



Comparison of Chemical Data 



The total nitrogen content of the samples of each type varies 

 within somewhat wide limits. The average amounts for the several 

 types are distinct, though the variations are such that some of the 

 quantities of one type overlap those of another type. It is believed 

 that for the types selected the field differentiations do indicate dif- 

 ferences. 



Regarding the humus content of the four types under considera- 

 tion, the results are somewhat different. The average amounts of 

 humus are almost alike in three of the four types, while the nitrogen- 

 poor San Joaquin soil has an average of about half that of the others. 

 Within the type the soils may be very nearly alike in the humus con- 

 tent, as is the case in two of the types, or may be widely variable, as 

 in the Hanford fine sandy loam. It should be noted that the amount 

 'of humus as shown by the method used, is not indicated by the inten- 

 sity of the color either of the soil or of the resulting extract. This 

 confirms the findings of Gortner, which are cited elsewhere. 



There was quite a wide range shown in the results of the deter- 

 mination of the loss on ignition. The Diablo and Altamont soils, be- 

 cause of the heavier textures and the relatively large amounts of com- 

 bined water, and of considerable amounts of CaC0 3 in at least one 

 case, gave high losses on ignition. The averages were close, 6.8% for 

 the Diablo, and 6.7% for the Altamont. The Hanford soils were 

 lower, though with a wider range. Soil no. 14, with 6.9% loss on igni- 

 tion, shows almost double that of any other soil in the type. The San 

 Joaquin soils, with an average of 2.6%, show the lowest average loss 

 on ignition. The smaller amounts of organic matter in these soils is 

 one reason for the smaller loss. . The two heavier types have averages 

 close together, and the lighter types have averages not far apart, but 

 because of the wide variations within each type, the results of the 

 determination of the loss on ignition certainly do not show that all 

 soils classified in one type are closely similar. 



Hall and Russell, in their discussion of the soils of southeastern 



England, 35 consider of value the ratio of j—v- — — r^— -but apply- 



% loss on ignition, 



ing this ratio to the California soils under consideration does not seem 



to give any relations of value. The Diablo ratio varies from 0.0136 to 



0.0158, the Altamont from 0.0141 to 0.0204, the San Joaquin from 



0.0144 to 0.0232, and the Hanford from 0.011 to 0.0172. 



30 Jour. Agr. Sci., vol. 4 (1911), pp. 182-223. 



