30 IRRIGATION FARMIXG. 



Glauber's salt and common salt do not possess this prop- 

 erty, the soils impregnated with them remain chiefly 

 white and are known as white alkali lands. 



Formation of Alkali Salts. Alkali is a natural 

 element of the earth, the same as other minerals. Wln-n 

 the rocks on the mountains pulverize and the sediments 

 wash down on the plains, they bring the alkali along and 

 deposit it in the soil. The same alkali salts are formed 

 everywhere in the world, but in countries having abun- 

 dant rainfall they currently wash through the soil into- 

 natural drainage, while in regions where rainfall is defi- 

 cient the scant moisture carries them down only a little 

 way into the soil, from which they rise to the surface by 

 the evaporation of water, and are thus accumulated at 

 or near the top of the soil. It is right thero that nearly 

 all the damage is done. The water in the depths of the 

 soil is rarely strongly enough impregnated to hurt the 

 roots of plants directly. The alkali is all through the 

 soil, but is usually worse within a few inches of the sur- 

 face. It rises to the surface with each wetting of the 

 ground, in the same manner as a wick. Different wicks 

 will raise water or coal oil to different hights, according 

 as they are closely woven, or loose like candle wi eking. 

 The close wick will raise the fluid higher in the end, but 

 it will raise to the highest point more slowly than with 

 the loose wicking. Just so in the soils. The close ones 

 will raise the soil water from a greater depth than will 

 the loose, sandy ones, but the latter will bring it up 

 quicker to the full hight to which it can rise. 



Soils Containing Alkali. Alkali is always worse 

 in clay soils than in sandy ones. This is because it rises 

 to the surface from a greater depth. In the arid coun- 

 try the rains often wet the soil only a few inches deep. 

 and the alkali forms at the bottom of the moisture and 

 makes hard cakes called hardpan, for hardpan is only a 

 soil full of alkali packed hard. We rarely come in con- 



