1914] Loughridge: Rumus and Nitrogen in Calif ornia Soil Columns 227 



would have greatly enriched the Mound soil with nitrogen from 

 the leguminous crop, but it seems to have produced but little if 

 any advantage over the orange orchard land ; in fact, the humus 

 of the latter is far richer in nitrogen, perhaps because of the use 

 of fertilizers. 



Santa Clara River Delta. — This comprises a broad region of 

 dark alluvial land and contains more or less alkali salts in places. 

 Water is usually found at a depth of eight or ten feet below the 

 surface. The delta is noted for its sugar-beet culture. A column 

 was taken near Springville by Mr. J. B. Neff to a depth of eight 

 feet, at which water was reached. 



Pleasant Valley Hill Slope.- — ^This column was taken from the 

 sandy slope of the hills north of the Southern Pacific Railroad 

 station of Camarillo. 



Table 28. — Humus in Soil Columns of Hillside and Delta of Santa 

 Clara Eiveb, Ventura County 



Range of most annual plant roots. 



