Timely Hints eor Farmers. 95 



this may be permissible; but in arid regions the alkali thus added, 

 plus that already present, may be injurious, while the potash, for 

 which the ashes are chiefly valuable, is already abundant in most 

 Arizona soils* 



R. H. Forbes, 



Department of Chemistry. 



WHITE ALKALI. 

 No. i2> MarCh 15. 



White Alkali, notwithstanding its fair name, is probably 

 guilty of greater crimes against agriculture in Arizona than its 

 "black" partner. This is because it is present in our soils in 

 much greater total quantity, although pound for pound it does 

 not do so much damage. 



The chief constituents of white alkali are common salt, and 

 sodium sulphate, better known as Glauber's salt. Chlorides and 

 sulphates of calcium and magnesium sometimes also occur, All 

 of these salts result from the weathering of certain rocks, especially 

 those of volcanic origin, and like all forms of alkali, though sol- 

 uble in water, remain in the soil because there is not sufficient 

 drainage to carry them away. In some parts of Arizona, deposits 

 of rock salt, and of calcium and sodium sulphates, probably formed 

 by the evaporation of ancient salt lakes, are exposed and find their 

 way into our rivers. Through irrigation and evaporation these 

 dissolved salts are carried upon cultivated lands and left there. 

 The origin and quality of our irrigation waters is therefore a mat- 

 ter of greatest importance. 



The white character of alkaline salts in southern Arizona is 

 shown by twenty analyses of virgin soils from Salt River Valley, 

 Which averaged about twice as much of sodium sulphate and 

 chloride as of sodium carbonate. As far as has been observed, the 

 same holds true of the upper Gila Valley. The Salt and Gila 

 rivers, also, at most times, carry only the white alkaline salts in 

 their upper courses. 



The quantity of these salts in a soil which may be endured 

 by vegetation varies according to the kind of crop, the variety of 



