214 University of California FuMications in Agricultural Sciences [Vol. 1 



(0.13 per cent) in the surface soil of Vacaville and Kenwood, 

 with the equivalent of about 5000 pounds per acre- foot ; the 

 general average of all surface soils being 0.10 per cent, or 4000 

 pounds per acre-foot. This is a very good amount. In a depth 

 of three upper feet, comprising the range of chief feeding roots 

 of the plant, we again find the highest percentage 'to be in the 

 Kenwood soil, with an average of 0.10 per cent for each foot, 

 or about 12,000 pounds of humus-nitrogen per acre in the three 

 feet. The Santa Rosa, Yountville, and Vacaville soils are nearly 

 equal in their amounts of 0.08 per cent. In the entire column 

 of twelve feet, the percentage of humus-nitrogen is greatest in 

 the Santa Rosa alluvial (0.05 per cent), while in the Russian 

 River alluvial and the Vaca Valley soils the percentage is 0.04 

 per cent. This high amount of humus-nitrogen in these soils 

 becomes gradually available to plants only through the action of 

 bacteria. 



The soils of the valleys north of the bay region may then be 

 considered as being well supplied in humus and humus-nitrogen, 

 which is well distributed throughout a depth of ten or twelve 

 feet, thus affording special inducements for deep rooting and 

 deep feeding of plants. 



The Bay Region 



Alameda Plains. — The bay shore rises gently eastward to the 

 foot of the Contra Costa Hills, a distance of about two miles. 

 On this slope the soil is largely of an adobe clay nature. The 

 city of Berkeley is situated on this slope, the University of 

 California being at the foot of the hills. A column of the clay 

 adobe was taken from the economic garden on the University 

 grounds. Southward from Berkeley and Oakland the slope 

 widens into a plain traversed by streams from the Coast Range 

 bordered by wide bands of a more loamy soil, and upon it are 

 found extensive farms. A column of the loam was taken from 

 the land of ]\Irs. Sanborn, south of Niles, and another from the 

 Meek place near Hayward. 



These are excellent soils, with fair humus and humus-nitrogen. 

 The Berkeley adobe is rich in nitrogen throughout. 



