462 



SOILS. 



Possible Injury to Land by Excessive Leaching. It should 

 not be forgotten, however, that excessive leaching of under- 

 drained land by flooding is liable to injure the soil in two 

 ways : first, by the removal of valuable soluble plant-food ; and 

 further, by rendering the land less retentive of moisture, such 

 retention being favored by the presence of small amounts of 

 alkali salts, not sufficient to injure crops. After the salts have 

 been carried down to a sufficient depth to prevent injury to 

 annual crops, and with proper subsequent attention to the pre- 

 vention of surface evaporation, the flooding will not need to 

 be repeated for several years. Thus in many soils excellent 

 crops may be grown even in strong alkali land, pending the 

 establishment of permanent drainage systems. 



The importance of thoroughly washing the alkali deeply into the 

 soil before the seed is planted, and keeping it there by proper means 

 until the foliage of the plant shades the soil sufficiently to prevent the 

 rise of moisture and alkali, is well illustrated in fields in the region of 

 Bakersfield, Cal., where alfalfa is now growing in soils once heavily 

 charged with alkali. From one of these fields samples of soil were 

 taken where the alkali was supposed to be strongest beneath the alfalfa, 

 and also from an adjoining untreated alkali spot, which was said to 

 represent conditions before alfalfa was planted. The results are given 

 in pounds per acre in four feet depth. 



Here the surface foot of the natural soil contained nearly 140,000 

 pounds of common salt, a prohibitory amount. Similar experience has 

 been had near Yuma, Arizona. 



Difficulty in Draining "Black" Alkali Lands. An import- 

 ant exception to the efficacy of draining, however, occurs in 

 the case of black alkali in most lands. Tn this case either the 

 impervious hardpan or (in the case of actual alkali spots) the 



l Bull. 133, Cal. Expt. Sta., by R. H. Loughridge. 



