1919] 



Pendleton : A Study of Soil Types 



401 



AUamont clay loam. — Here the variations in the humus content 

 (table 17, and fig. 16) are small in the A horizon, 1.1% to 1.3%. The 

 average is 1.24%. The B and C samples show a good parallelism 

 among themselves, but not so good when compared with the surface. 

 The average of the B horizon is 0.81V' , and of the C horizon 0.57%. 



% 



9 



\ 



\ 







-V 



\ 



\ 



A 



\ 



\ 



\ 



\ 



\ 



^r 



\ 



\ 



V 



/ 



/ 



/ 



/ 



V 



y 



Loss on 

 A Ignition 



^L- 





MgO 



K 2 



Humus 



3 4 7 Soils 



Fig. 16. Graph showing the loss on ignition, the amount of humus, and the 

 percentages of calcium, magnesium, and potassium in the three samples of Alt a 

 niont clay loam. 



San Joaquin sandy loam. — This type contains a considerable quan- 

 tity of humus (table 18, and fig. 17) when one takes into considera- 

 tion the popular criteria for the presence of humus, for the red to 

 reddish brown San Joaquin soils are very different from the brown 

 Altamont or the black Diablo soils. The samples of this type gave 



