1914] Loughridge: Humus and Nitrogen in Calif ornia Soil Columns 215 



Table 20. — Humus in Soil Columns of Alameda Plains, Alameda County 



Berkeley Haywaed Niles 



Humus- Humus- Humus- 

 Soil Nitrogen in Soil Nitrogen in Soil Nitrogen in 



Clav 31.93 , '^ , Clay 9.21 , ^ , Clay 10.76 , -^ , 



Ft. Humus Humus Soil Humus Humus Soil Humus Humus Soil 



1 Black clay .... 2.13 6.67 .14 Loam 1.81 4.65 .08 Dark loam .... 1.10 5.36 .06 



2 Black clay .... 2.07 5.97 .12 Loam 1.04 5.67 .06 Dark loam .... 1.00 4.20 .06 



3 Black clay .... 1.84 7.33 .14 Loam 74 6.26 .05 Dark loam 78 5.04 .04 



4 Black clay .... 1.90 4.68 .09 Loam 80 4.73 .04 Dark loam 56 5.01 .03 



5 Yellow clay.. .95 7.05 .07 Loam 92 4.58 .04 Dark loam 44 5.74 .03 



6 Yellow clay.. 1.06 5.37 .06 Loam 78 6.48 .05 Dark loam 38 5.17 .02 



7 Yellow clay.. .48 16.45 .08 Loam 68 6.18 .04 Dark loam 40 5.27 .02 



8 Yellow clay.. .37 24.10 .09 Loam 57 5.26 .03 Dark loam 62 8.15 .05 



9 Yellow clay.. .36 12.50 .05 Loam 38 7.90 .03 Dark loam 70 4.01 .03 



10 Yellow clay.. .36 14.70 .05 Sandy 32 6.58 .02 Dark loam 68 4.54 .03 



11 Yellow clay.. .45 9.35 .04 Dark loam 41 6.85 .03 Dark loam 56 4.51 .03 



12 Yellow clay.. .49 8.16 .04 Dark clay 80 1.28 .01 Dark loam 46 6.10 .03 



Sumof per cents 12.46 9.25 7.68 



Average per foot 1.04 10.20 .08 .77 5.53 .04 .64 5.25 .03 



Upper 3 feet : * 

 Sum of per cents 6.04 3.59 2.88 



Average per foot 2.01 6.70 .13 1.19 5.60 .06 .96 4.90 .05 



* Range of most annual plant roots. 



East of Contra Costa Hills. — Eastward across the Contra 

 Costa hills several narrow valleys connect the large and fertile 

 Livermore Valley with the bay shore on the north, and repre- 

 sentative columns of soils were taken from three of these. 



Ignacio Valley. — Along Walnut Creek there is a narrow belt 

 of black clay-loam soil bordered by land more adobe-like in 

 nature which extends to the low mesa and hills. The higher land 

 on the mesa and bordering it in the valley has a stiff and black 

 adobe clay soil about three feet in depth and underlaid by a 

 whitish material. The column of the former was obtained from 

 the place of Professor F. T. Bioletti, one mile north of Walnut 

 Creek, Contra Costa County. 



San Ramon Valley. — This valley is a continuation southward 

 of Walnut Creek Valley, but wider and with more extensive 

 black adobe soils, a column of which was obtained in the vicinity 

 of San Ramon post office, Contra Costa County. 



