PHOSPHORUS 187 



one million for home consumption, and an equal amount for 

 exportation, chiefly to Great Britain, Germany, and other parts 

 of Europe. 



It is estimated that the total phosphate deposits of the world 

 thus far discovered will still furnish 'somewhere from 200 million 

 to 500 million tons of high-grade phosphate rock. Some phosphate 

 deposits have recently been found in Wyoming, Idaho, and Utah, 

 and doubtless still other extensive deposits will be discovered in 

 various parts of the earth; but, nevertheless, the world's total 

 supply of high-grade phosphate is apparently very limited when 

 measured by crop requirements, as evidenced by the enormous 

 shipment of phosphate from America to Europe, despite the exten- 

 sive and long-continued search by geologists for any undiscovered 

 European deposits. (See also Appendix.) 



Facts worthy of careful consideration are that the Chilian gov- 

 ernment derives a large revenue from export duties on sodium 

 nitrate, from the world's greatest natural deposits of combined 

 nitrogen, an element which the Chilian landowners can always 

 secure, however, from the inexhaustible atmospheric supply; 

 whereas, from the United States we are exporting half of our total 

 production of phosphates with no restrictions, although we are 

 thus shipping away from our lands the only element we shall ever 

 need to purchase in order to maintain the fertility of our own soils. 

 The laws of Norway greatly restrict the exportation of phosphate 

 from that country. 



To restore to the soils of the United States the phosphorus 

 removed by the corn crop alone, would require the annual applica- 

 tion of our total annual production of phosphate rock, counting 

 23 pounds of phosphorus for a hundred-bushel crop of corn, and 

 2\ billion bushels as the average corn crop of the United States. 



The Florida phosphates are classed chiefly as hard rock and soft 

 rock, the South Carolina phosphates as land rock and river rock; 

 and the Tennessee phosphates as brown rock and blue rock. The 

 quality is usually expressed as percentage of purity; that is, 

 percentage of tricalcium phosphate. 



The South Carolina land rock is the lowest in phosphorus, averag- 

 ing less than 50 per cent calcium phosphate, or less than 10 per cent 

 of phosphorus. The South Carolina river rock and the Florida 



