COMMEMCIAL FEBTILIZEMS 511 



preparation or in their composition. Another discrep- 

 ancy arises from the fact that all soils do not respond in 

 the same relative degree to any one fertilizer. Thus, 

 Sackett ^ found that in some soils dried blood was am- 

 monified more rapidly than was cottonseed meal, while 

 in other soils the reverse was true; and that a similar 

 difference obtained in soils with respect to the ammoni- 

 fication of alfalfa meal and flaxseed meal. It would 

 therefore appear to be impossible to make any close dis- 

 tinctions in the relative availability of the nitrogen in 

 various organic nitrogenous fertilizers. A considerable 

 number of these experiments are, in the aggregate, useful 

 in pointing out the probable relative availabilities of the 

 more widely differing nitrogen-bearing substances. 



FERTILIZERS USED FOR THEIR PHOSPHORUS 



Phosphorus is generally present in combination with 

 lime, iron, or alumina. Some of the phosphates contain 

 also organic matter, in which case they generally carry 

 some nitrogen. Phosphates associated with organic 

 matter decompose more quickly in the soil than do un- 

 treated mineral phosphates. 



430. Bone phosphate. — Formerly bones were used 

 entirely in the raw condition, ground or unground. When 

 ground they act as a fertilizer more quickly than when 

 unground. Raw bones contain about 22 per cent of phos- 

 phoric acid and 4 per cent of nitrogen. The phosphorus 

 is in the form of tricalcic phosphate (Ca3(P04)2). 



Most of the bone now on the market is first boiled or 



1 Sackett, W. G. The Ammonifying Bfficiency of Certain 

 Colorado Soils. Colorado Agr. Exp. Sta., Bui. 184, pp. 3-23. 

 1912. 



