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



The two clay soils from Santa Clara and Gilroy are rich in 

 humus to depths of three and four feet respectively, and in the 

 latter tlie percentage is quite large through the entire column. 



In the Santa Clara column there is a sudden and great fall 

 in percentage below the third foot, where the color also sharply 

 changes from very black to gray. In this soil the clay percentage 

 is very high, producing such a compact and severe texture as 

 to prevent the downward distribution of any mass of plant roots. 



The El Quito soil, if a true representative of the orchard 

 lands of the west side of the valley, clearly lacks a sufficient 

 supply of humus in the upper surface foot, though lower down 

 in the column the percentage is very fair. A soil from Cupertino 

 also had a low percentage in its surface foot ; the humus, how- 

 ever, in both the El Quito and Santa Clara soil is surprisingly 

 poor in nitrogen. A green-manure crop, rich in nitrogen, is 

 clearly needed to produce conditions for high fertility. The 

 Gilroy column has a fair amount of nitrogen. 



