1914] Loughridge: Mumus and Nitrogen in California Soil Columns 217 



The humus in the Berkeley clay is surprisingly rich in 

 nitrogen — that of the eighth foot reaching 24 per cent — but 

 otherwise the general average of the entire column is 10.20 per 

 cent, which is higher than has been thus far observed in any of 

 the columns except the tule marsh of Stockton. The percentage 

 of nitrogen in the humus of the other five columns is not especi- 

 ally high. For the upper three feet of the Berkeley column the 

 average of humus-nitrogen in the soil is 0.13 per cent, or approxi- 

 mately 5200 pounds for each foot. This is a high amount and 

 is probably largely due to the excellent cultivation the soil has 

 had for years past. 



The percentage of humus in the sandy loam soil taken near 

 Santa Rita in the central part of Livermore Valley is surprisingly 

 low in the upper part of the column, and, as a result, the sur- 

 face was found dry and crusted over to such an extent that 

 it had to be broken up before the auger could be used. Green- 

 manure crops should be grown and turned under for several 

 successive years in this soil, for by this the texture of the soil 

 would be improved, more nitrogen introduced, and better crops 

 obtained. A comparison of the soils of the two sections shows 

 that those of the bay shore are richer in humus and in nitrogen, 

 both in the surface foot, in the surface three feet, and in the 

 entire column, than those east of the Contra Costa hills. 



South of the Bay Region 



Santa Clara Valley. — This valley, reaching from the Bay of 

 San Francisco southward for seventy miles into San Benito 

 County has a variety of soils. Around the bay, back from the 

 salt marshes, there is a black clay adobe. A column of this was 

 taken from the Morse Seed Farm near Santa Clara. 



South of San Jose the lands are more loamy in character and 

 are represented by a column taken from near Gilroy, by ]\Ir. F. 

 E. Johnson. 



The valley west of San Jose has a soil more sandy in nature 

 and more or less gravelly, on which is located extensive orchards. 

 A column of this soil, seemingly representative of this land, was 

 taken from the El Quito ranch south of Saratoga. 



