EXPERIMENT STATION BULLETINS. 



645 



TABLE 9.— THE EFFECT OF WATER TABLE (TWELVE INCHES FROM THE SURFACE 

 ' ON SALT MOVEMENT. DURATION OF EXPERIMENT 43 DATS. 



CL.4Y LO.VM 



3iinch... 



4 inches . 



8 inches . 

 12 inches. 



}i inch. . . 



4 inches. 



8 inches . 

 12 inches. 



Fixe S.\n"d. 



Medium Sand. 



3.30 

 .022 

 .015 

 .017 



Still another series was run in which the water table was maintained 

 twenty-four inches from the surface. The salt remained very near the 

 surface inasmuch as the freezing point lowering of the soil four inches 

 from the .surface were the same in botli treated and untreated soils of 

 the same class. 



RAINFALL AND SOLUBLE SALT CONTENT OF SOILS. 



The rainfall affects the amount of soluble salts in the soil. The rate 

 at which different added salts are removed by washing as well as. their 

 residuary affect upon the soluble constituents of the soil has been ex- 

 tensively investigated by Bouyoucos. the results of which are in the 

 press. In this report however, are given the results of certain studies 

 of the effect of rain upon the salt content of the soil under field condi- 

 tions. Samples of soil have been taken before and after rains. In addi- 

 tion the effect of different amounts of added water has been considered. 



The data in table 15 shows that a two-inch rainfall on muck lands that 

 are slightly below the optimum water content for plant growth greatly 

 reduces the salt content of the surface layer and takes portions of it a 

 few inches below, yet there still remains appreciable quantities in the 

 surface layer of soil. Samples were also taken from several soil classes, 

 where the growth of vegetation was prevented, before and after 1.3 inches 

 of rainfall. The effect of this amount of precipitation was found to be 

 measurable as the data in table 10 show. 



