THE TREATMENT OF ALKALI. 39 



sive adlion exerted by the alkali salts upon the root 

 crowns and upper roots of plants is the most common 

 source of injury, there is another kind of damage 

 which manifests itself, 'mainly in the heavier class of 

 soils thus afflidled, when the soluble salts consist 

 largely of carbonates of soda and potash. This is the 

 great difficulty, or almost impossibility, of producing a 

 condition of true tilth, in consequence of the now well- 

 known tendency of alkaline solutions to maintain all 

 true clay in the most impalpably divided or tamped 

 condition, that of well- worked potter's clay, instead of 

 the flocculent condition it assumes in a well-tilled soil. 



Waters Carrying Alkali. — There are some 

 classes of water which it is not advisable to use for 

 purposes of irrigation. Thus it was at one time pro- 

 posed to use the waters of Kern and Tulare lakes in 

 California for irrigation, but careful investigation 

 showed that these waters were strongly alkaline and 

 that their continued use would deposit on the surface 

 a sufficient coating of salt to render the lands sterile. 

 The beds of these lakes are coated with a deep stratum 

 of alkali. Similarly some artesian waters, and even 

 the waters from some flowing streams, like the Salt 

 Creek in Southern Arizona, for instance, would result 

 in the produdlion of alkali. 



Alkali is chiefly the result of defedlive irrigation by 

 permitting evaporation of sub-surface water, thereby 

 leaving alkali on the surface ; but the largest propor- 

 tion of damage is brought about by the rise of the sub- 

 surface water-level by lateral soaking from high-line 

 canals, and the trouble is greatly aggravated and ex- 

 tended by the extravagant use of water. 



