544 SOILS: PBOPEMTIES AND MANAGEMENT 



The effect of sodium chloride on clay-bearing soils 

 is to liberate certain plant nutrients, among which are 

 calcium, magnesium^ potassium, and phosphorus. This 

 action, although limited in amount, is probably, in some 

 cases at least, partly responsible for the beneficial action 

 of common salt. 



The structure of the soil is improved by the applica- 

 tion of sodium chloride, just as it is by lime, although 

 usually not to the same extent. 



Another effect of salt is to conserve and distribute 

 soil moisture. Its conserving action is probably due to 

 an increase in the density of the soil-water solution, thus 

 retarding transpiration. The film movement of water is 

 likewise increased by the presence of salt in the solution, 

 and in this way the upward movement of bottom water 

 is facilitated and the supply within reach of the roots 

 maintained in time of drought. 



It has been seen that sodium is not one of the substances 

 essentiaUo the growth of plants. But that sodium may 

 be substituted, in part, for the potassium absorbed by 

 agricultural plants in their normal growth, has been 

 shown in this country by the experiments of Wheeler 

 and Adams ; ^ and the more ready availability of the 

 sodium applied as a chloride than of the potassium in 

 its natural condition in some soils probably accounts in 

 part for the beneficial effects of this salt. 



It is not all soils, however, that are benefited by salt, 

 its usefulness not being of such wide application as that 

 of lime. Certain crops, as previously mentioned, are 

 injured by the presence of chlorine. 



1 Wheeler, BT. J., and Adams, G. E. Coneeraing tlie Agri- 

 cultural Value of Sodium Salts. Rhode Island Agr. Exp. Sta.. 

 Bui. 106. 1905. 



