1919] Pendleton: A Study of Soil Types IM 



SUMMARY 



Presumably typical samples of four soil types were collected for 

 laboratory and greenhouse study from widely distributed Localities in 

 the state of California. The field appearance of each sample was 

 usually sufficient to warrant the classification as it exists. 



Physical Relations 



1. The mechanical analysis by the Hilgard elutriator shows that 

 the soils of a given type are in some cases quite divergent from each 

 other in their content of certain of the sizes of partich s. The mechan- 

 ical analysis by the Bureau of Soils method shows that 6 of the '_' 1 

 soils were not true to their type names, and that of those soils within 

 the type there is considerable variation. 



2. The moisture equivalents for the several types show distinct 

 enough values to substantiate the field separation. 



3. The hygroscopic coefficients vary widely within each type and 

 the types are not shown to be distinctly different by this criterion. 



Chemical Relations 



1. The total nitrogen averages vary markedly from type to type, 

 with the Altamont clay loam containing three times that in the San 

 Joaquin sandy loam. 



2. The average humus content of the San Joaquin samples is 

 about half that of the other types. The variations in the humus con- 

 tent between the types are small, considering the diverse nature of the 

 types and the large range in the amount of humus within the type. 



3. The loss on ignition shows a considerable variation within the 

 type and no significant distinction between the four types. 



4. The average total calcium content of the types is distinct, 

 though the wide range within each type minimizes the significance of 

 the variation in the averages. 



5. With regard to magnesium, the types are neither distinct nor 

 are the soils within the type closely similar. 



6. The average phosphorus content of the types is distinct, though 

 the ranges within the several types frequently overlap. 



7. The total potassium results do not show the types to be distinct 

 nor the soils within a type closely similar. 



