November, 1920] tertilizee inspection, 1920. 5 



low-priced fertilizer may have a much greater agricultural 

 value upon a certain soil than a high-priced fertilizer and 

 upon another soil the opposite might be true. In selecting 

 a fertilizer it is therefore just as important that the farmer 

 consider the needs of his particular soils and crops as it is 

 to secure the commercially cheapest fertilizer. This sug- 

 gests the real need for more experimental work to determine 

 the fertilizer needs of the soils of our state. 



METHOD OF CALCULATING RELATIVE COMMER- 

 CIAL VALUE. 



The commercial value of a fertilizer is based upon the 

 content of available nitrogen, "phosphoric acid" (P2O5) 

 and potash (KjO). If we know the guaranteed analysis 

 and the commercial value of a pound of each of the plant 

 foods, we can calculate the relative values of fertilizers. 



The terms unit of nitrogen, unit of phosphoric acid or 

 unit of potash are sometimes used to express the amounts 

 instead of the per cent. The term "unit" means 20 lbs. 

 per ton (2000 lbs.) or 1 per cent. One unit then means 1 

 per cent of a ton or 20 lbs. A fertilizer having 3 per cent 

 nitrogen has three units of nitrogen per ton, or 60 lbs. per 

 ton. 



It is impossible to give accurate figures for the cost of 

 the different plant foods for the past season because, due 

 to unsettled conditions, there were rather wide fluctuations. 

 The following list of prices, however, approximates the cost 

 to the manufacturers of the ingredients for mixed fer- 

 tilizers. 



To these must of course be added the cost of mixing, 

 bagging, freight and manufacturers' and dealers' profit to 

 obtain the sale price. For the comparison of the relative 

 value, however, these figures will be satisfactory. 



