THE SOIL SOLUTION 



285 



of the solution in these soils through the growing season by 

 the freezing point method corroborates the conclusions drawn 

 from the water extracts. The investigation also indicates that 

 large amounts of nutrients are made available by cultivation, 

 fallowing, and cropping and that, from the standpoint of the 

 soil solution, the ordinary farm practices are inherently sound. 

 Hoagland 's data regarding some of the soils studied is given 

 in Table LXIII. The moisture content was approximately the 

 same for each soil. 



Table LXIII 



THE CONCENTRATION OF THE SOIL SOLUTION IN PARTS PER MIL- 

 LION FROM A GOOD AND POOR SOIL EACH FALLOWED OR 

 CROPPED TO BARLEY. 



Further investigations of Hoagland with Martin x indicate 

 that the effect of cropping on the soil solution persists for 

 a considerable period. A marked relationship was also noted 

 between the soil solution and the physical condition of the 

 soil, due to a change in the colloidal matter with season. An 

 increase in colloidal matter was noted when the soil solution 

 was depleted of its solutes by plant activities. 



1 Hoagland, D. E., and Martin, J. C, Effect of Season and Crop 

 Growth on the Physical State of the Soil; Jour. Agr. Res., Vol. XX, 

 No. 5, pp. 397-404, 1920. 



