208 University of California Publications in Agricultural Sciences [Vol. 1 



The humus of both plains and the red lauds is fairly 

 rich in nitrogen; but the amount for the soil itself is below the 

 normal of 0.05 per cent minimum, except in the first foot. These 

 lands therefore need not only more humus but a humus that is 

 very rich in nitrogen. A leguminous crop, such as the spring 

 vetch, should alone be used for humification, for by it the land 

 secures a greater amount of green stuff, a far greater amount 

 of nitrogen than if grass, rye, or alfileria were used, and such 

 nitrogen is derived chiefly from the atmosphere. 



SOIL COLUMNS OF THE LOWER FOOTHILLS OF SIERRA NEVADA 



The lower foothills of the Sierra Nevada rising from the 

 valley plains to an elevation of 2500 feet above sea-level forms 

 an important fruit-bearing region. The soils derived from slate 

 and granite are often shallow on the hillsides but deep in the 

 valleys. 



Table 18. — Humus in Soil Columns of Foothills 



Range of most annual plant roots. 



