CHAPTER XI 



MOVEMENT OF SOLUBLE SALTS THROUGH 



THE SOIL 



The greatest problem connected with the utilization of 

 alkali lands is control of the movement of soluble salts. 

 Were it possible to handle the land economically so that 

 the movement of the alkali would be continually down- 

 ward into the subsoil, or better, into the drainage system 

 where it would be permanently removed from the feeding 

 zone of the plants, the alkali problem would be solved. 

 The upward translocation of enormous quantities of 

 soluble salts into the top foot or two of soil has ruined 

 vast areas of the most productive lands of the arid regions. 



Salts in Natural Soils. Where undisturbed by flooding 

 and where the water-table is a considerable distance be- 

 low the surface, soluble salts tend to accumulate at some 

 distance beneath, rather than at the surface of arid soils. 

 The rainfall is light and frequently so distributed that the 

 moisture penetrates to a distance of only 3 to 4 feet 

 in most soils. Much of the water that enters the soil 

 is needed by the plants growing upon it and this water is 

 extracted some distance below the surface. A large part 

 of the movement of salts is in connection with capillary 

 action, and because the capillary movement of moisture 

 to the surface of the soil is reduced by the rapid drying 

 out of the surface soil, little of the water is allowed to 

 evaporate at the surface and deposit its soluble salts. 



Since there is little movement of water except through 



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