EXPERIMENT STATION BULLETINS. 655 



TABL,E 21.— EFFECT OF PLANT GROWTH ON THE SOLUBLE SALT CONTENT OF SOILS. 



It seems justifiable to conclude that under the condition of these 

 experiments, that is relatively small volumes of soil, the soluble salt 

 content of soil may be largely utilized by the plants thus reducing the 

 concentration of the soil solution to a minimum. Whether this j)he- 

 nomenon occurs in the field where the quantity of soil exposed to the 

 action of the plant roots is very large, is more doubtful. 



B. FIELD STUDIES. 



To throw some light upon this question several classes of soil were 

 sampled under different crops. For comparison small areas were scraped 

 free of vegetation early in the spring and maintained so throughout 

 the season, both virgin and adjacent field soils being included. On 

 June 13th samples were taken of the surface ^,4 inch and of the soil imme- 

 diately below to depths of six and twelve inches, respectively. Con- 

 tamination of the lower sections was prevented by inserting a metal tube 

 to the depth of six inches and taking the sample through it. The samples 

 were taken directly to the laboratory, spread out in a thiu layer, allowed 

 to become air dry, made up to a uniform water content and the freezing 

 point lowerings determined in the usual manner. 



The results are presented in table 22. 



