SECTION XVIII. CALCULATING FERTILIZER 

 FORMULAS 



FERTILIZERS are sometimes spoken of as chemicals. 

 Those made by mixing any two such chemicals are called 

 mixed, manufactured, or manipulated fertilizers. The laws 

 of most states require that there shall be printed on the out- 

 side of each bag of fertilizer a statement showing the per- 

 centage of nitrogen, phosphoric acid, and potash it contains. 

 No fertilizer should be bought until the buyer has calcu- 

 lated its commercial value from these figures on the bag, 

 using the method shown on page 103. After he has 

 calculated the commercial value, he should compare this 

 figure with the cash price asked by the seller. The two 

 figures should differ by only enough to pay the dealer a 

 fair profit and the cost of freight. 



The commercial value of a pound of nitrogen, phosphoric 

 acid, and potash is the average wholesale selling price of 

 these substances in the largest fertilizer markets. Chemists 

 average these prices every year, and publish the figures as 

 the commercial values for that year. Generally the com- 

 mercial value is about 1 5 cents per pound of nitrogen, 5 

 cents per pound of available phosphoric acid, and 5 cents 

 per pound of potash. 



How to calculate the commercial value. Multiply the 

 prices given above by the number of pounds of nitrogen, 

 available phosphoric acid, and potash respectively in a ton 



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