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



Surface foot Upper 3 feet Entire column 



Yuba City, Sutter County 2,000 lbs. 4,800 lbs. 11,200 lbs. 



Chico, Butte County 2,000 lbs. 4,800 lbs. 10,800 lbs. 



Stockton, San Joaquin County 2,000 lbs. 3,600 lbs. 11,600 lbs. 



Russian River, Sonoma County 2,800 lbs. 9,600 lbs. 26,400 lbs. 



Santa Paula, Ventura County 2,800 lbs. 7,200 lbs. 15,600 lbs. 



Santa Clara, Santa Clara County.... 2,800 lbs. 4,800 lbs. 20,400 lbs. 



Modesto, Stanislaus County 400 lbs. 1,200 lbs. 3,200 lbs. 



Even in the upper foot of each of the above there is from 

 2000 to 2800 pounds, with the exception of tnat of ^Modesto, which 

 has only 400 pounds of phosphoric acid per acre. 



When we consider the fact that 0.05 per cent or 2000 pounds 

 per acre of available phosphoric acid is regarded as a sufficient 

 amount for soil fertility for present needs, we can readily see 

 that these particular soils, except that from Modesto, are abund- 

 antly supplied with phosphoric acid for many years. 



Analyses of the first, sixth, and twelfth foot respectively of 

 the columns also show the presence of large percentages of 

 available potash. 



Comparison of Arid and Humid Soils 



A comparison between the soils of the arid and humid regions 

 brings out the very great advantage possessed by the former and 

 especially by those of California over the humid, as shown in the 

 first part of this bulletin. But it is especially marked in the 

 amount and distribution of humus in the soils of the respective 

 region.^- The general average in 280 soils of the humid portion 

 of the United States is 2.63 per cent, and if we add to this the 

 5.26 per cent in eleven tropical soils of Hawaii the average is 

 brought to 2.73 per cent, or approximately 109,200 pounds per 

 acre in a depth of twelve inches. 



The average of the 331 California soils and forty-four from 

 Idaho, Arizona, and Oregon is 1.28 per cent for the surface foot, 

 or less than one-half that of the humid region. For the first 



1- It has been a rather difficult matter to secure data on humus in the 

 soils east of the Mississijjpi River for the reason that in their analysis 

 some of the chemists have failed to separate it from the percentage of 

 aggregate "organic matter." 



