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



tendency to form a plowsole and to make the soil loose and of 

 good texture for a downward development of the grain roots, 

 which may thus secure the benefits of the humus, would tend 

 greatly to increase the grain yields of the valley. This was shown 

 in the experiments of Professor G. W. Shaw at Ceres and Tulare,^ 

 where during a period of three years by this method the average 

 yield of wheat was thirty-five and thirty-three bushels respec- 

 tiveh', during which period the average wheat for the state was 

 14.5 bushes per acre. No irrigation or fertilization was used in 

 his experiments. 



The humus-nitrogen of the upper three feet of the composite 

 column is 6.27 per cent of the humus, which is higher than in 

 any of the other composite columns in the table. In the soil 

 itself, however, there is but an average of 0.04 per cent, or 1600 

 pounds per acre-foot. 



Sierra Nevada Foothills. — The composite of three columns 

 from the Sierra Nevada foothills shows more humus in the first 

 foot than in that of the Sacramento Valley or Southern Cali- 

 fornia. That of the second foot is, however, somewhat less, and 

 there is a greater decrease in the lower part of the column, the 

 sum being but 3.39 per cent in the eight feet. ]\Iore than one- 

 half of the humus is held in the upper three feet. 



The humus-nitrogen in the upper three feet of the composite 

 column is 5.4 per cent of the humus, or 0.05 per cent in the soil, 

 and is equivalent to 2000 pounds for each acre-foot in the three 

 feet. 



Coast Range Valleys. — The composite column of the twenty- 

 four soils of the valleys of the Coast Range shows a general 

 average of nearly 2 per cent of humus in the surface foot and thus 

 is far above each of the other columns, except the marshes and 

 meadowlands. Not only that, but it is the only composite column 

 of the uplands which ha.s more than 1 per cent in the subsoils 

 immediately below the first foot. The percentage of humus in 

 each of the succeeding feet throughout the twelve feet is also 

 higher than in any other of the composite columns; the twelfth 

 foot has nearly one-half of 1 per cent and the sum of the entire 

 column is 9.38 per cent. The humus is not a.s rich in nitrogen 



8 Bull. No. 211, Calif. Agr. Exp. Sta. 



