CHAPTER X 

 PHOSPHATE FERTILIZERS 



Although nitrogen is the most expensive fertilizing 

 element the farmer buvs and is usually considered the most 

 important, phosphorus is actually the element which should 

 cause him the greatest concern. The soil contains no more 

 phosphoric acid than nitrogen, the average of good culti- 

 vated soil being not far from 0.15 to 0.2 per cent. Phos- 

 phorus is necessary for the production of seed, inducing 

 early and full maturity. It occurs for the most part in the 

 grain at harvest and is thereby sold from the farm, little 

 being left in stems and leaves to be returned to the soil as 

 litter. Finally, phosphorus cannot be added to the soil 

 by the growth of any special crop. It is not like nitrogen 

 which can be obtained by legumes from the exhaustless at- 

 mospheric source. Phosphorus must be purchased and added 

 to the soil, or the soil becomes exhausted. Supplies brought 

 up from the subsoil either by capillarity or the growth of 

 deep rooted crops are not sufficient to add materially to the 

 amount in the surface soil. Continued cropping and no return 

 result in a loss of phosphorus. Phosphate fertilizers, then, 

 are of prime importance. 



169. Raw Bone. — Bones when fresh contain about 40 

 per cent, of organic matter, 53 per cent, of inorganic matter 

 and 7 per cent, of water. The organic matter consists of 

 fat and ossein, the latter a nitrogenous compound. The 

 inorganic matter is mostly tricalcium phosphate, Ca3(PO.i)2. 

 It comes on the market as raw bone-meal, and coarse ground 

 bone, containing about 4 per cent, nitrogen and 22 per cent, 

 phosphoric acid. The presence of the fat makes fine grinding 

 impossible and it is not used much as a fertilizer. The 

 fat prevents bacterial action, thus checking nitrification, and 



