ALKALI SALTS 



397 



soil. Certain of the alkali salts exert a deflocculating 

 action on clay soils and effect an indirect injury in that 

 way. 



Fig. 57. — Diagram showing the amount and composition of alkali salts 

 at various depths. Tulare, California. 



308. Accumulation of alkali. — The alkali salts, being 

 readily soluble, are carried by the soil water where there 

 is any lateral movement, as is often the case where land 

 slopes to some one point. Low-lying lands adjacent to 

 such slopes are thus likely to contain considerable alkali, 

 and the " alkali spots " of semiarid regions and the 

 large accumulations of alkali in many of the valley lands 

 of arid regions are traceable to this cause. 



309. Irrigation and alkali. — In irrigated regions, the 

 injurious effect of alkali is in many cases discovered only 



