190 THE FARMER OF TO-MORROW 



a problem of restoring the balance, giving this 

 or that mineral opportunity to catch up. 



The practice of maintaining fertility by 

 means of chemicals is of course the logical 

 sequence of such a theory. If a growing plant 

 has destroyed the balance of the mineral 

 nutrients in the soil, what is more simple than 

 to restore that balance by adding the required 

 nutrients so that all crops may have at all 

 times their optimum amount of "available" 

 food? 



The following quotations from Edward B. 

 Voorhees (Fertilizers. Fourth ed., 1902) sets 

 forth the established schools of practice in the 

 use of commercial fertilizers that have grown 

 out of the theories of Liebig: 



"Pages 182-185. The one [system of fer- 

 tilization] which has perhaps received the 

 most attention, doubtless largely because one 

 of the first presented, and in a very attractive 

 manner, is the system advocated by the cele- 

 brated French scientist, George Ville. This 

 system, while not to be depended upon ab- 

 solutely, suggests lines of practice which, 

 under proper restrictions, may be of very 

 great service. In brief, this method assumes 

 that plants may be, so far as their fertiliza- 

 tion is concerned, divided into three distinct 



