ALKALI 119 



ing or "crumbing" agencies, and if not present in too large 

 amounts tend to increase the readiness with which the soil can 

 be brought into good tilth. In this latter case, by separating in 

 the solid phase, or in forming a viscous soil solution, near the 

 saturation point, they sometimes produce a condition in the soil 

 simulating puddling, and where it occurs below the surface, called 

 an alkali hard-pan. 



The management of soils infested with alkali is possible in 

 accordance with a few well established principles. Substantial 

 progress has been made in selecting and breeding plants and 

 strains of plants adapted to such soils. Extreme cases are the 

 use of the so-called Australian salt-bushes as forage crops, and 

 the growing of date-palms which through generations of breed- 

 ing in the oases of the Sahara can thrive in lands so salty as 

 to destroy most of the halophilous plants. More interesting is 

 the unwitting development of the farmers of Utah of strains of 

 wheat and alfalfa which easily withstand three or four times as 

 high a salt content in the soil as do corresponding crops in other 

 alkali regions, such as New Mexico and Arizona. 1 Black alkali, 

 or one in which sodium carbonate is a prominent constituent, 

 is especially destructive to vegetation, not alone on account of a 

 toxic action on plants, but because in any considerable concen- 

 tration it has a corrosive action on the plant tissue. Not only 

 on this account but also because of its unfortunate effects on 

 the physical properties of the soil, black alkali has received un- 

 usual attention from soil investigators. Hilgard 2 has repeated- 

 ly urged the use of gypsum as an "antidote" to black alkali, as- 

 suming that under conditions of good drainage and aeration a 



1 Some mutual relations between alkali soils and vegetation, by 

 Thomas H. Kearney and Frank K. Cameron, Report No. 71, U. S. Dept. 

 Agriculture, 1902; The date-palm and its utilization in the Southwestern 

 states, by Walter T. Swingle, Bull. 53, Bureau of Plant Industry, U. S. 

 Dept. Agriculture, 1904; The comparative tolerance of various plants 

 for the salts common in alkali soils, by T. H. Kearney and L. L. Harter, 

 Bull. 113, Bureau of Plant Industry, U. S. Dept. Agriculture, 1907; 

 Tolerance of alkali by various cultures, by R. H. Loughridge, Bull. 133, 

 California Agr. Expt. Sta., 1901. 



2 Soils, by E. W. Hilgard, 1906, pp. 457-458. 



