242 SYSTEMS OF PERMANENT AGRICULTURE 



There are several points especially favorable to the use of natural 

 rock phosphate where proper conditions can be provided: 



The first is the fact that phosphorus in fine-ground raw phos- 

 phate can be obtained, delivered to the heart of the corn belt, for 

 about 3 cents a pound, or for $7.50 for a ton of phosphate contain- 

 ing 250 pounds of phosphorus, or perhaps $9.00 for a ton contain- 

 ing 300 pounds of phosphorus; while phosphorus will cost about 

 10 cents a pound in steamed bone meal, 12 cents a pound in acid 

 phosphate, and about 30 cents a pound in ordinary so-called com- 

 plete fertilizers. In the adoption of systems of permanent agri- 

 culture, one can easily afford to apply to the soil, in natural phos- 

 phate, larger quantities of phosphorus than are removed in the 

 largest crops, and thus provide a truly permanent system with 

 respect to phosphorus. 



The second point is that lower grades of phosphate can be used 

 for direct application to the soil than can be utilized in the manu- 

 facture of acid phosphate. For acid-phosphate manufacture the 

 raw material must be not only high in phosphorus, but it must be 

 low in certain forms of impurities, such as iron and aluminum 

 compounds, which, if present, require much larger use of sulfuric 

 acid and also make an unsatisfactory product; but phosphates of 

 moderate phosphorus content and even with considerable iron and 

 aluminum present, which have hitherto been left on the dump piles 

 as worthless, are now being used for direct application to the land 

 in connection with liberal amounts of farm manure or clover or 

 other forms of decaying organic matter. Other low-grade phos- 

 phates are being mined and ground for direct use. If 12^ per 

 cent phosphate (62^- per cent tricalcium phosphate) is worth $7.50 

 per ton, then 10 per cent phosphate (50 per cent pure) is worth 

 $6.00 a ton; and even 8 per cent phosphate (160 pounds of phos- 

 phorus per ton) is worth $4.80 a ton, which would allow $2.00 a 

 ton for the fine-ground phosphate on board cars in bulk at the mine, 

 and $2.80 for freight, the average rate from the Tennessee phosphate 

 district to southern Illinois points. The possibility of using these 

 low-grade phosphates, of which there are immense deposits, is of 

 enormous importance in the general adoption of permanent sys- 

 tems of soil improvement. 



A third point in favor of raw phosphate, in common with bone 



