EXPERIMENT STATION BULLETINS. 185 



AGRICULTURAL VALUE, 



The agricultural value of a fertilizer is entirely distinct from the com- 

 mercial value. The two have no true relation. The agricultural value 

 of a fertilizer is measured by the value of the increase of crop produced 

 by its use, and is naturally variable depending on many conditions. It is 

 unquestionably true that any fertilizer has a greater agricultural value 

 in some localities than in others, depending of course upon the character 

 of the soil and somewhat upon the crop grown, at the same time however, 

 the commercial value woijld be practically the same regardless of the 

 localit3% 



Commercial fertilizers should be selected with the view of supplement- 

 ing the natural resovirces of the soil and the manures produced upon 

 the farm, consequently the agricultural value of the fertilizer would 

 depend largely upon how wisely this selection was made. 



COST OF COMMERCIAL FERTILIZERS. 



It is probably true that a large percentage of the farmers using com- 

 mercial fertilizers are largely influenced in their selection of a particu- 

 lar brand by the selling price, without giving due regard to the amount 

 and kinds of plant food it contains. That this is so is evidenced by the 

 large number of low and medium grade fertilizers found on sale through- 

 out the state. 



The particular value of a commercial fertilizer is to furnish to the 

 growing crop the necessary elements of plant food, that is, nitrogen, 

 phosjjhoric acid and potash, which the soil is no longer able to furnish 

 in sufficient quantities. That fertilizer, then, which will supply the 

 nitrogen, phosphoric acid and potash, in available forms, at the least 

 cost per pound should be selected. It matters little under what name 

 it is sold. 



For the purpose of studying more closely the variation in the com- 

 position and cost per pound of the plant food elements, an arbitrary 

 division has been made of complete fertilizers into four separate classes, 

 based upon their commercial valuation; that is, the price at which the 

 separate unmixed materials in one ton of fertilizer could be purchased 

 for cash at retail in the larger fertilizer centers, such as Detroit and 

 Chicago. 



Our classification is as follows: 



1. Low-grade fertilizers, those having a commercial valuation of less 

 than flO.OO a ton. 



2. Medium-grade fertilizers, those having a commercial valuation 

 greater than $16.00 and less than |20.00 a ton. 



3. Medium high-grade fertilizers, those having a commercial valua- 

 tion greater than |20.0i3 and less than 125.00 a ton. 



4. High-grade fertilizers, those having a commercial valuation greater 

 than 125.00 a ton. 



The 123 complete fertilizers analyzed are distributed among the four 

 classes as follows : 



Low-grade 29 or 23.0 per cent. 



Medium-grade .• 48 or 30. " " 



Medium high-grade 23 or 18.7 " " 



High-grade 23 or 18.7 " " 



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