400 



Journal of Agricultural Research 



Vol. XX, No. s 



It is evident that there exists a very good general correlation between 

 the quantity of soluble constituents in the soil and the quantity of sus- 

 pended material and that in both cases the magnitudes undergo very 

 marked variations coincidentally with seasonal changes and crop growth. 

 These fluctuations are far more pronounced, however, in the cropped 



e 



16 

 24- 



"f-0 

 4-8 

 56 

 64- 

 72 

 SO 

 66 

 96 

 /Of- 

 112 

 J 20 



pPS?" 



XT' 



CROP B/9RLEY 



7/ PL/9 NTS 



TUf?B/DtTY T//Q 



VJSC--0 



CfPOR A/ON£ 



Fig. 3. — Effect of crop on physical state and electrolyte concentration of the water extract of the soil. 



soils than in the uncropped soils. In other words, it is a fair conclusion 

 that the absorption of solutes by the plant has lowered the concentra- 

 tion of the soil solution at a period of 8 or 10 weeks after planting and 

 that the physical state of the soil has undergone an equally definite 

 change. It can scarcely be doubted that there is some definite relation 

 between the concentration and composition of the soil solution and the 



