no MAINE AGRICQLTUBAL EXPERIMENT STATION. I914. 

 RULES FOR CALCULATING VALUATION OF FERTILIZERS. 



The commercial valuation will be accurate enough as a mean? 

 of camparison if the following rule is adopted: 



Multiply 3.9 by the percentage of nitrogen. 



Multiply 0.8 by the percentage of available phosphoric acid. 



Multiply 0.4 by the percentage of insoluble phosphoric acid. 



Multiply i.o by the percentage of potash. 



The sum of these 4 products will be the commercial valua- 

 tion per ton on the basis taken. 



Illustration. The table of analyses shows a certain fertilizer 

 to have the following composition : Nitrogen 3.30 per cent ; 

 Available phosphoric acid 8.00 per cent; Insoluble phosphoric 

 acid 1. 00 per cent ; Potash 6.00 per cent. The valuation in this 

 case will be computed thus : 



Nitrogen, 3-9X3-30 $12 87 



Available phosphoric acid, 0.8X8.00 6 40 



Insoluble phosphoric acid, 0.4X1-00 40 



Potash, 1.0X6.00 6 00 



$25 67 

 Potash in 191 5 Fertilizers. 



While there are twenty odd elements that enter into the com- 

 position of plants, nitrogen, phosphorus, potasium and calcium 

 are the important ones added in commercial fertilizers. Al- 

 though an acre of fertile soil contains tons of nitrogen, phos- 

 phoric acid and potash they are usually in forms unavailable to 

 plants. Growing plants take up and carry off in the resulting 

 crops a large amount of the available nitrogen, phosphoric acid, 

 potash and lime in a given soil. If the crops are fed upon the 

 farm and the resulting manures are saved a large part of the 

 manurial matter in a good available form will be returned to 

 the land. If, however, the crops are sold from off the farm 

 the farm is depleted by this loss of plant food which must be 

 made good in some way or other. Usually manures are applied 

 to soil for the double purpose of applying plant food in an avail- 

 able form and unlocking the unavailable compounds which are 



New England agriculture has been dependent for the last 

 generation upon the purchase of plant food to supplement that 

 already in the soil. 



