

FIXATION 197 



largely to the physical and chemical action of the soil 

 solution. The soil solution from different soils varies 

 with the composition and degree of disintegration of 

 the soil particles, and in the same soil at different times 

 there are variations in its composition. The soil solution 

 is more important as an agent for bringing about chem- 

 ical and physical changes in the soil than as a store- 

 house of plant food. It is not possible to exhaust a soil 

 of all of its water-soluble salts by one or more leachings. 

 There appears to be a variable but fairly continuous 

 solubility of soil constituents. King has shown that 

 soils of high productiveness contain a larger amount of 

 soluble salts than soils of low fertility. 97 



