COMMERCIAL FERTILIZERS 209 



example could be made from feldspar rock, apatite 

 rock, and leather. The leather contains nitrogen, 

 the apatite contains phosphoric acid, and the feldspar, 

 potash. Such a fertilizer would have no value when 

 used on a crop, because all of the plant food elements 

 are present in unavailable forms. Hence, in purchas- 

 ing fertilizers, it is necessary to know not only the 

 percentage composition, but also the nature of the 

 materials from which the fertilizer was made. 



267. Inspection of Fertilizers. — In many states 

 laws have been enacted regulating the manufacture 

 and sale of commercial fertilizers, and provision is made 

 for inspection and analysis of all brands offered for 

 sale. The label on the fertilizer package must specify 

 the percentage amounts of nitrogen, available phos- 

 phoric acid and potash. Inspection has been found 

 necessary in order to protect the farmer and the honest 

 manufacturer. 



Occasionally a fraud is revealed like the following : 7 ° 



Natural plant food $25 to $28 per ton. 

 Composition. Per cent. 



Total phosphoric acid 22.21 



Insoluble " " 20.81 



Available " " 1.40 



Potash soluble in water o. 13 



Actual value per ton, $1.52. 



268. Mechanical Condition of Fertilizers. — When 

 a fertilizer is purchased, the mechanical condition 

 should also be considered. The finer the fer- 



