CROPS AND SOIL IMPROVEMENT 



as the purchase of bone that has been treated 

 in any way for removal of various substances 

 in it. 



Steamed Bone. When animal bone is boiled 

 or steamed under pressure for removal of the fat 

 and the cartilage, the content of nitrogen is re- 

 duced, and the percentage of phosphoric acid is 

 increased by this removal of fat and nitrogenous 

 substance. The nitrogen in steamed bone may 

 run as low as 1 per cent, and the phosphoric acid 

 may go up to 30 per cent. The composition of 

 steamed bone is so widely variable that the name 

 means little, and purchase should be made only 

 on guaranteed analysis. Some grades run very 

 low both in nitrogen and phosphoric acid, due 

 probably to adulteration. 



The boiling or steaming of bone makes fine grind- 

 ing possible, and the fineness and absence of fat 

 permit quick decay in the soil. Steamed bone 

 is an excellent source of phosphoric acid. The 

 availability is less immediate than that of acid 

 phosphate, but much greater than that of raw bone. 



Rock-phosphate. While the greater part of 

 our soils contains relatively scant stores of phos- 

 phoric acid, the deposits of this plant constituent 

 in combination with lime are immense. The rock 



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