EFFECT ON PLANT GROWTH OF SODIUM SALTS IN 



THE SOIL 



By Frank B. Headley, Superintendent, Truckee-C arson Field Station, E. W. Curtis, 

 Scientific Assistant, and C. S. ScoField, Agriculturist in Charge, Office of Western 

 Irrigation Agriculture, Bureau of Plant Industry 



INTRODUCTION 



In connection with an attempt to utilize for crop production certain 

 salty land on the Truckee-Carson Field Station, at Fallon, Nev., it has 

 been necessary to make numerous determinations as to the limit of the 

 salt content of the soil tolerated by crop plants. These determinations 

 have shown that this limit of tolerance is not a fixed and definite point, 

 but is instead extremely variable. Not only is it influenced by many 

 factors, such as kind of soil, kind of salt, and kind of plant, but the same 

 crop plant shows marked differences in tolerance at different periods of 

 its growth. These facts make the problem of dealing efficiently with 

 the reclamation of alkali land a very complex one.' 



In the present instance the more abundant and deleterious salts are 

 those of sodium. These sodium salts occur as carbonates, bicarbonates, 

 chlorids, and sulphates, and the proportions of each in different parts of 

 the field are extremely variable. This variability of the proportions in 

 which these salts occur confused the results of the early attempts to 

 determine the limits of tolerance for the different crope. In order to 

 establish a basis from which to proceed with the work, a series of pot 

 cultures was carried on in which the soils were artificially impregnated 

 with solutions of the different salts. These experiments have served to 

 show the limit of tolerance to each of the four salts of one crop, wheat, 

 in the seedling stage. They have also brought out a point which has not 

 generally been taken into account in similar experiments — that the 

 limit of tolerance of plants is dependent not upon the quantity of salt 

 added to the soil but upon the quantity which exists in the soil solution 

 and which is recoverable from the soil by water digestion. 



It appears that the discrepancy between the amount of salt added to a 

 soil and the amount which can be later recovered from it is sometimes 

 very great. Different soils show different results in this respect; and 

 some of the salts, particularly the carbonates and sulphates of sodium, 

 are absorbed by the soil to a greater extent than sodium chlorid. Thus, 

 if the limit of tolerance of a plant is given in terms of the quantity of salt 

 which must be added to a soil to inhibit growth, this limit will be found 



1 For literature germane to this subject see Harris, F. S. Effect of alkali salts in soils on the germina- 

 tion and growth of crops. In Jour. Agr. Research, v. 5, no. 1, p. 52-53. 1915. 



Journal of Agricultural Research, Vol. VI, No. 23 



Dept. of Agriculture, Washington, D. C August 28, 1916 



2 G-93 



(857) 



