376 THE SMALL GRAINS 



very finely divided particles and, in the Palouse country, 

 have, in recent times, been shifted* by wind action and 

 deposited as dunes. In California the principal cereal 

 section lies in the flood plains of the Sacramento and 

 San Joaquin rivers. In many places the soil is heavy and 

 sticky, and, when dry, is worked with much difficulty. 

 The Imperial valley soil is an enormous silt deposit 

 brought by the Colorado River and said to be over 700 

 feet deep in places. 



404. Topography and drainage. The surface features 

 between mountains in most of this area are similar to 

 those of the Great Plains, except as to the plant cover, 

 which, wherever there is any, is composed generally of 

 shrubs instead of grasses, because of the lack of summer 

 rains. The volcanic soils of the northwest absorb and 

 hold water tenaciously. The usually light precipitation 

 makes drainage, of course, unnecessary, under dry-farm- 

 ing. There is, however, much irrigation throughout the 

 area, and wherever that is practiced, drainage is very 

 necessary to prevent excessive deposits of alkali. These 

 deposits at or near the surface constantly increase through 

 irrigation, until they become a serious menace to the crop, 

 unless the applications of water are moderate or there is 

 good drainage. 



405. Soil amendments. Acid soils are found occa- 

 sionally in the Pacific Coast lands, but in the Western 

 area generally there is little need of lime for correcting 

 soil acidity. Lime, in many places, may be of use in 

 loosening heavy, clay, adobe soils. Under irrigation, 

 gypsum may be profitably used in some localities, as a 

 corrective for sodium carbonate called " black alkali." 

 Potassium is rarely needed for present uses, and a potash 

 fertilizer will not, therefore, usually need to be applied, 



