96 Bulletin No. 34. 



soil, drainage and method of cultivation. In general from o. 1 to 

 0.5 per cent of alkaline salts, according to the kind, is fatal to most 

 cultivated crops. Sulphate of soda is least harmful, common salt 

 next, and carbonate of soda most injurious of the three. 



On this point Dr. Hilgard says that for barley the largest 

 amount of alkaline salts that can be tolerated in the soil and sub- 

 soil, under otherwise favorable conditions, and with salts consist- 

 ing of not over half of carbonate of soda, lies somewhere bstween 

 .150 and .203 per cent of the soil. Whitney and Means state that 

 "The limit of excess of alkali in the soils at Billings (Montana) 

 * was found to be about .45 of one per cent. 



This is equivalent to about 15,000 pounds par acre one foot deep." 

 The character of the alkali at Billings is stated to be entirely 

 "white" thus permitting' the presence of a larger percentage than 

 if carbonate of soda were present. 



As in the case of black alkali, white alkali does most of its 

 damage near the surface of the soil. When in solution in ground 

 or irrigating water it is carried with the water wherever it goes, 

 until evaporation occurs, when it can no longer follow. 



At the surface of the soil, therefore, where evaporation takes 

 place, the alkali concentrates until it is locally destructive to plants. 

 It follows that where and when evaporation is greatest this pro- 

 cess of concentration is most rapid. In hot and windy weather, 

 or in exposed situations the "rise of the alkali" for this reason 

 occurs most promptly. 



The most effective cure for white alkali is removal by flooding 

 and drainage. This method of course requires abundant water 

 and good drainage, and can by no means be applied to all situ- 

 ations. Some of the most alkaline districts in Arizona are very 

 favorably situated for drainage. South of Tempe, in the Buckeye 

 country, and on the upper Gila, water is comparatively abundant, 

 and these lanis, being underlaid in some localities by gravel and 

 lying near the river, are admirably drained. There should be 

 little difficulty in flooding the alkali from at least portions of all 

 these districts. 



But where water is scarce and drainage is poor, other expedients 

 must be take n. Deep cultivation is one of these. The more deeply 

 an alkaline crust is plowed under the longer will it take to again 



