200 THE FARMER OF TO-MORROW 



should be considered in this connection. The 

 first is the question of commercial fertilizers. 

 If the productivity of the soil of a State de- 

 pends ultimately and literally upon our re- 

 turning an equivalent amount of plant-food 

 constituents to the soil to replace that re- 

 moved by the crop, then the life of the nation 

 will ultimately depend upon the available de- 

 posits of nitrates, phosphates, and potash 

 compounds. It is clearly impossible with the 

 available data to give any expression of the 

 amount of such replacement which has been 

 made in the past, but from what we know, 

 so far as the actual importation of mineral 

 material foreign to the farm is concerned, it 

 is negligible. 



"The use of commercial fertilizers is not old. 

 The potash deposits of Germany were first 

 worked in 1862, the phosphate deposits of 

 South Carolina in 1868. Phosphates were dis- 

 covered in Florida in 1888 and in Tennessee 

 in 1894. It may be said that the general use 

 of commercial fertilizers began in the United 

 States about the year 1865. 



"The other matter which should receive at- 

 tention is the influence of material in the form 

 of foodstuffs imported from less densely set- 

 tled countries to those of greater population 

 as a possible source of introducing foreign 

 mineral matter to maintain the productivity 

 of the soil of the older and more densely set- 



