SOME MUTUAL RELATIONS BETWEEN ALKALI SOILS 

 AND VEGETATION. 



THE EFFECT UPON SEEDLING PLANTS OF CERTAIN COMPONENTS 



OF ALKALI SOILS. 



By Thomas H. Kearney and Frank K. Cameron. 

 INTRODUCTION. 



Everyone who is familiar with alkali soils knows that their charac 

 ter varies greatly in different localities, one salt or combination of 

 salts i^redominating over others which may he present.^ Sometimes 

 sodium carbonate, the dreaded ''black alkali," is relatively abundant 

 as compared with the other soluble soil components. In other cases 

 this salt may be entirely absent or present merely as a trace, while 

 one or more of the "white alkali" salts, e.g., sodium chloride or 

 sodium sulphate, plays the most important part. 



It is also known that these salts are not all equally injurious to veg- 

 etation. Sodium carbonate, for instance, is generall}^ believed to be 

 much more harmful than any other salt of common occurrence, owing 

 probably to its pronounced corrosive action on the plant tissues. 

 Gypsum, or the dihydrate of calcium sulphate, on the other hand, is 

 harmless and even beneficial in ordinar}^ cases. Experiments with 

 solutions of chemically equivalent strength show very marked differ- 

 ences in the action of different salts upon plant growth. Hence the 

 question whether the salt forming the greater part of the soluble com- 

 ponents of a given soil is, to take a concrete case, the very injurious 

 sodium carbonate or the relatively harmless sodium chloride, may 

 often determine whether that soil is utterly useless or quite valuable 

 to the farmer. 



It becomes, therefore, a question of great importance to everj^one 

 who is concerned with soils which contain an appreciable amount of 

 alkali to know definitely the relative harmfulness of the salts both 

 severally and in mixtures, since the latter is the condition under 

 which the}^ almost invariably occur in nature. 



Field observations will give some idea of how the soluble salt com- 

 ponents compare in this regard. But the conclusions are necessarily 

 somewhat vague and unsatisfactory; for in the field and under the 

 conditions that are found in nature it is practically impossible to study 



^See Bulletin No. 17, Division of Soils, U. S. Department of Agriculture (1901), 



7 



