8 CONTROL SERIES NO. 122 



For the smallest size packages intended almost solely for use on small lots of 

 potted plants, the total amount expended by any one individual is so small 

 that the economic factor is hardly worth considering. In this case the convenience 

 of handling a small package and the lack of odor or dust while applying the fer- 

 tilizer to the plants probably far outweigh the extra cost, especially so far as most 

 women are concerned. However, the amount spent for fertilizer for average 

 outside garden use is large enough, especially if hydroponic fertilizer is purchased, 

 to justify examination of the value the purchaser Is getting for his money. 



The preceding table lists the average price the consumer pays for each pound 

 of plant food (nitrogen, phosphoric acid, and potash) in purchasing any of the 

 brands listed. For example, in ten pounds of a 4-8-4 grade there are 4 tenths 

 of a pound of nitrogen, 8 tenths of a pound of phosphoric acid, and 4 tenths of a 

 pound of potash, or a total of 1.6 pounds of plant food, considering onh' the three 

 major elements. If the ten pounds of fertilizer sells for $1.00, the average cost 

 per pound of actual plant food is 1.00 divided by 1.6, or 62.5 cents a pound. It 

 ma\' be said here that most of the minor elements are needed in such small quan- 

 tities that their cost compared to that of the major elements is practically neg- 

 ligible. 



Calculation of Shortages 



For calculating the approximate commercial shortages per ton the following 

 figures were used: 



Retail Cost 

 Per Unit 



Nitrogen: 



Water-soluble and synthetic organic $2.00 



Water-insoluble of good quality and 



Water-soluble amounting to one-eighth of the percentage of 

 water-insoluble nitrogen found when the percentage of 

 water-insoluble nitrogen exceeds .50 8.00 



Available phosphoric acid 1.40 



Potash : 



Muriate '. 85 



Sulfate 1.10 



From cotton hull and boll ashes and wood ashes 1.26 



These values represent the a\'erage retail cost to the consumer of the plant 

 food elements In unmixed materials. This does not include mixing and overhead 

 costs which increase the retail cost of these elements In mixed goods. 



To compensate for the Increased unit cost in mixed goods the commercial 

 shortage as found by using our values is multiplied by the factor: Actual retail 

 selling price divided by our calculated guaranteed value. 



Example: A 5-8-7 fertilizer selling for $39.00 a ton analyzes: 



Total nitrogen 4.67 



Water-insoluble nitrogen .88 



Available phosphoric acid 7.43 



Potash 7.13 



Shortage: Nitrogen 33, X$2.00 = $0.66 



Available phosphoric acid 57 X 1.40 = .80 



Total $1.46 



