. Principles of agricultural chemistry [microform] . Fig. 63.—Alkali spot remaining in reclaimed field, Utah. Bureau of Soils. sition of rocks. In climates where there is an abundance of rain,and much water passes through the soil, the alkali salts are^ Headdeu, Bulletin 178, Colorado Station. 26o principle;s of agricultural chemistry washed out about as fast as they are formed and carried intostreams, and thence to the sea. In arid climates, since the rainfall is not sufficient to wash outthe soluble salts, they accumulate. As long as these salts are dis-tributed uniformly through the mass of
. Principles of agricultural chemistry [microform] . Fig. 63.—Alkali spot remaining in reclaimed field, Utah. Bureau of Soils. sition of rocks. In climates where there is an abundance of rain,and much water passes through the soil, the alkali salts are^ Headdeu, Bulletin 178, Colorado Station. 26o principle;s of agricultural chemistry washed out about as fast as they are formed and carried intostreams, and thence to the sea. In arid climates, since the rainfall is not sufficient to wash outthe soluble salts, they accumulate. As long as these salts are dis-tributed uniformly through the mass of the soil, they cause no POUNDS OF SALT PEIR SOOOO 15,000 eOflOO 35,000. Fig. 64.—Salt content of sandy land and of gumbo soil, before and after irrigation. Irrigation causes the alkali to rise to near the surface of the gumbo soil. Bureau of Soils. injury, but the alkali may accumulate in the surface-foot of thesoil, or it may be carried away to accumulate in another field. When water comes in contact with the soil, it dissolves thesoluble constituents as far as it penetrates. If afterwards it SOIL Df;FiciENciEs 261 rises and evaporates, it leaves there all the alkali which it held insolution. Thus the alkali originally distributed through the soilmay be concentrated near the svuface, thereby causing injury toplants. Checking evaporation by cultivation, mulching or shad-ing the land by crops, will check the rise of alkali. It sometimeshappens that the alkali is concentrated in the eleventh or twelfthfoot of the soil. Under moderate irrigation, the water will notpenetrate to this depth, but excessive irrigation will carry waterto such depths as to dissol
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