THE SOIL AS AN ASSET 233 



These experiments established one con- 

 clusion, i. e., that the rate at which plant food 

 enters solution in the soil is available, in 

 other words is fixed within narrow limits and 

 that it always tends toward an equilibrium 

 as the plant extracts its "food." Thus con- 

 tinuous leachings do not rob the soil of its 

 capacity for furnishing fresh solutions of fixed 

 densities and the addition of highly soluble 

 fertilizer salts, such as muriate of potash, or 

 ammonium phosphate, does not seem to affect 

 the density of the solution. The soil merely 

 absorbs the excess, holds it in reserve. 



A solution of 10 parts per 1,000,000 is al- 

 most infinitesimal, yet it is sufficient to support 

 plant growth, as has been shown by hundreds 

 of experiments. Average soil solutions cover- 

 ing thousands of experiments give about 27.3 

 parts of potash and 8.5 parts of phosphoric 

 acid. Do such low concentrations sustain and 

 promote plant life? 



Undoubtedly they can, and actually do. 



Many years ago it was found that mature 

 crops of good yield could be grown in well 

 water containing only 18 parts of potash and 

 2 parts of phosphoric acid. And very satis- 

 factory growth of wheat was obtained from 



