224 University of Calif ornia PuMications in Agricultural Sciences [Vol. 1 



columns there is a decrease downward, indicating that the 

 humification was of plant roots rather than of vegetable matter 

 deposited from overflow as the land was being built up. 



A comparison of the results of the examination of the first 

 foot gives an average of 2.08 per cent of humus north of the 

 bay, 1.82 per cent for the bay region, and 1.93 for the region 

 south, while for the three upper feet the averages are 1.55, 1.59, 

 and 1.45 per cent respectively. This shows quite a close agree- 

 ment in the soils of the valleys of the three divisions. 



A glance over the tables brings out the fact that the Santa 

 Clara soil has a higher amount of humus (4. -43 per cent) in the 

 tirst foot than any soil of the state, except the marsh soils, and 

 that nine of the twenty-five columns of the Coast Range have 

 more than 2 per cent in the surface foot, while in all others but 

 two there is more than 1 per cent. 



The portion of the soil column lying below the first foot is 

 richer in humus than that of other agricultural regions. There 

 is more than 1 per cent in each of the four upper feet of ten 

 of the twenty-four columns of the Coast Range; in the columns 

 from Santa Rosa, Russian River, AValnut Creek, and Berkeley 

 this percentage extends through five feet, while in the soil from 

 Lompoc and Arroyo Grande it reaches through seven feet. 



The humus of the Santa ]\Iaria soil is richest in nitrogen, 9.57 

 per cent, that of Livermore Valley being next with 8.78. The 

 surface soils whose humus is poorest in nitrogen according to 

 the analyses are King City and Santa Clara adobes. The general 

 average for the twenty-four columns is 5.36 per cent. 



The percentage of nitrogen in the surface soil is highest in 

 the soils from Arroyo Grande, viz., 0.16 per cent, or approxi- 

 mately 6400 pounds per acre. Gilroy has 0.15 per cent, Berkeley 

 0.14 per cent, Lompoc, Vacaville, and Kenwood 0.13 per cent 

 each, and Santa Clara, El Verano, Santa Maria, and Yountville 

 each has more than 0.10 per cent. 



Humus in ihe Upper Three Feet. — The percentage of humus 

 in the upper three feet has a summation of 10.89 for the Santa 

 Clara, a little more than 6 per cent for Gilroy, Berkeley, and the 

 two Arroyo Grande columns, and 5.57 per cent for Lompoc, but 

 all others are below this. 



