314 PRINCIPLES OF AGRICULTURAL CHEMISTRY 



Commercial Valuation. The commercial value of a fertilizer is 

 the selling price of the plant food ingredients as determined by 

 market and trade conditions. The agricultural value, or crop- 

 producing power, often has no relation to the commercial or mar- 

 ket value of the material. Thus it frequently happens that an 

 element costs less in a highly available form than in a less avail- 

 able form. Organic nitrogen may cost more than nitric nitrogen, 

 while the nitric nitrogen is more available and would have a 

 greater crop-producing power if properly applied. 



The commercial value is usually fixed by the cost of the plant 

 food in the raw materials in ton lots at retail, and frequently at 

 the seaboard. Cost of transportation must be added. Fluctua- 

 tions in the values take place according to trade conditions. 



An illustration of the commercial value is as follows : Suppose 

 that 14 per cent, phosphoric acid costs $16.80 a ton. A ton con- 

 tains 14x20 = 280 pounds available phosphoric acid, so that one 

 pound costs 6.0 cents. This is the commercial or trade value. 



If the commercial valuation of phosphoric acid is 6 cents, 

 potash 6 cents and nitrogen 20 cents, it does not follow that a 

 pound of nitrogen will give an increase of crop worth 20 cents, 

 or that a pound of phosphoric acid will give a 6 cent increase, or 

 that the effect will be in that ratio. 



1911 



Cents per pound 



Nitrogen in nitrates 16.0 



Nitrogen in ammonia salts 16.0 



Organic nitrogen in dry and fine ground fish and blood- 23.0 



Organic nitrogen in cottonseed meal and castor pomace- 21.0 

 Organic nitrogen in fine ground bone and tankage and 



mixed fertilizers 20.0 



Organic nitrogen in coarse bone and tankage 15.0 



Phosphoric acid soluble in water 4.5 



Phosphoric acid soluble in ammonium citrate 4.0 



Phosphoric acid in fine ground bone and tankage 4.0 



Phosphoric acid in coarse bone and tankage 3.5 



Phosphoric acid insoluble (in water and in ammonium 



citrate ) in mixed fertilizers 2.0 



Potash in high grade sulphate and in mixtures free from 



muriate (chloride) 5.0 



Potash as muriate 4.5 



Potash in cottonseed meal and castor pomace 5.0 



