400 



University of California Publications in Agricultural Sciences [Vol.3 



Humus 



Diablo clay adobe. — The variations in the humus content of the A 

 samples (table 16, and fig. 15) are moderate, 1.1% to 1.4%, while the 

 B and C horizons do not agree so closely with each other or with the 



% 



9 



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/ 



/ 



/ 



/ 



-J- 



/ 



/ 



/ 



/ 



-/- 



/ 



-X 



Loss on 

 Ignition 



MgO 



K 2 



Humus 



.— CaO 



6 Soils 



Fig. 15. Graph showing the loss on ignition, the amount of humus, and 

 the percentages of calcium, magnesium, and potassium in the four samples 

 of Diablo clay adobe. 



surface foot. The average content of humus in the A samples is 

 1.26%, in the B samples 0.95%, and in the C samples 0.75%. It is 

 worthy of note that soil no. 2, with the lightest color of the four, and 

 what might be supposed to be a lower humus content, has next to the 

 highest amount. 



