1914] Loughridge: Humus and Nitrogen in California Soil Columns 245 



Table 39. — Humus in Soil Columns of Pitt River and Butte Valleys 



Pitt River Valley Butte Valley 



MODOC COUNTY SISKIY'OU COUNTY 



Altueas Klamath 



Humus- Humus- 

 Soil Nitrogen in Soil Nitrogen in 



Clay 29.60 , -^ , Clay 11.00 , ^ ^ 



Ft. Humus Humus Soil Humus Humus Soil 



1 Clay 3.05 1.93 .06 Marsh loam.. 3.75 9.15 .34 



2 Clay 1.45 3.39 .05 Marsh loam.. 3.20 7.10 .23 



3 Clay 1.01 5.85 .06 Marsh loam.. 3.02 9.07 .27 



4 Clay 87 3.22 .03 Marsh loam.. 2.84 8.88 .25 



5 Clay 51 1.09 .01 Ashy loamt - .91 7.70 .07 



6 Clay 34 1.65 .01 Ashy loamf - .74 7.58 .06 



7 Water Dark clay 06 



8 Dark clay .... tr. 



Sum of per cents 7.23 14.52 



Average per foot 1.20 2.85 .03 1.81 8.25 .20 



Upper 3 feet : * 



Sum of per cents 5.51 9.97 



Average per foot 1.84 3.72 .06 3.32 8.44 .28 



* Range of most annual plant roots, 

 t Infusorial earth. 



Both of the above soils are rich in humus, though differing 

 greatly in other respects. The Alturas is a clay soil under culti- 

 vation in alfalfa, and while its humus is poor in nitrogen the 

 amount given to the soil is fair. On the other hand, the Klamath 

 column is from tule-marsh lands, containing a larger proportion 

 of decaying vegetable matter, and consequently is quite rich in 

 humus. The latter is especially rich in nitrogen and as a con- 

 sequence the soil is also well supplied in nitrogen through its 

 upper four feet. The fifth and sixth foot are largely made up of 

 diatomaceous earth in which the humus has suddenly diminished 

 to less than 1 per cent. 



Surprise Valley. — Eastward from Alturas, the Warner range 

 of mountains separates the Pitt Riv'Cr Valley from Surprise 

 Valley with its three large lakes. The land of the eastern side 

 of this valley is strongly charged with alkali salts, but on the 

 west the broad slope from the mountains to the lake presents 

 excellent agricultural capabilities, the production of alfalfa seed 

 being quite a prominent industry. A column of soil ten feet deep 



