DAVIS] STUDIES OF COMMERCIAL FERTILIZERS 125 



values quoted are nitrogen 19 cents, phosphoric acid 6 cents, 

 and potash 6 cents. On this basis the value of 32.8 pounds of 

 nitrogen at 19 cents is $6.23 ; of 160 pounds of phosphoric acid at 

 6 cents is $9.60; of 60 pounds of potash at 6 cents is $3.60. 



(3) Add the values thus obtained in (2) : $6.23 plus $9.60 

 plus $3.60 = $19.43. The selling price of such a fertilizer may- 

 be from $27 to $30 a ton, or at a profit of $7.57 to $10.57. This 

 profit covers cost of mixing, freight, storage, agent's commission, 

 loss from credit and bad debts. 



In buying a complete commercial fertilizer the total value of 

 plant food should be calculated, and this amount subtracted from 

 the dealer's price. The difference should not exceed a reasonable 

 allowance for profit,^ — ^for example, if the total value of plant food 

 is $19.43 per ton and the dealer's price is $30.00 a ton, the difference 

 or profit of $10.57 is "too great. 



Problems: 



1. Find the value of plant food in a ton of 1-10-4 fertilizer. 



2. If a 4—8—4 fertilizer sells at $32 a ton and 1-7-5 fertilizer 

 at $26 a ton, which fertilizer allows the greater profit to the dealer? 



3. A fertilizer tag shows the following guaranteed analysis: 



Water 12 to 14 per cent 



Ammonia 2 " 3 " 



Available phosphoric acid 8 "10 " 



Phosphate of lime 21 "25 " 



Insoluble phosphoric acid 2.5 " 3 " 



Potash 8 " 9 " 



Sulfate of potash 12 " 14 " 



What is the percentage each of nitrogen, phosphoric acid, and 

 potash that should be considered in estimating the value of this 

 fertilizer ? 



4. Secure from dealers lists of fertilizers containing guaranteed 

 analyses and prices per ton. Calculate food value of plant food 

 in each and compare with selling price. Sometimes prices are 

 quoted at so much per unit. A unit is 20 pounds. To find price 

 of a ton multiply price of one unit by 100. 



Application: 



These problems illustrate a practical application of arithmetic 

 in estimating the value of a commercial fertilizer. One should 



