266 AGRICULTURAL EXPERIMENT STATION. [Jan. 



of different brands of fertilizers does not necessarily stand 

 in a direct relation to their particular fitness, without any 

 reference to the particular condition of the soil to be treated 

 and the special wants of the crops to be raised by their 

 assistance. 



To select judiciously from among the various brands of 

 fertilizers offered for patronage requires, in the main, two 

 kinds of information, namely, we ought to feel confident 

 that the particular brand of fertilizer in question actually 

 contains the guaranteed quantities and qualities of essential 

 articles of plant food at a reasonable cost, and that it con- 

 tains them in such form and such proportions as will best 

 meet existing circumstances and special wants. In some 

 cases it may be mainly either phosphoric acid or nitrogen or 

 potash ; in others, two of them ; and in others again, all 

 three. A remunerative use of commercial fertilizers can 

 only be secured by attending carefully to the above-stated 

 considerations. 



To assist farmers not yet familiar with the current mode 

 of determining the commercial value of manurial substances 

 offered for sale in our markets, some of the essential con- 

 siderations, which serve as a l^asis for their commercial 

 valuation, are once more stated within a few subsequent 

 pages. 



The hitherto customary valuation of manurial substances 

 is based on the average trade value of the essential fertil- 

 izing elements specified by analysis. The money value of 

 the higher grades of agricultural chemicals and of the higher- 

 priced compound fertilizers depends, in the majority of 

 cases, on the amount and the particular form of two or three 

 essential articles of plant food, i. e., phosphoric acid, nitro- 

 gen and potash, which they contain. To ascertain by this 

 mode of valuation the approximate market value of a fertil- 

 izer (z. e., the money worth of its essential fertilizing in- 

 gredients), we multiply the pounds per ton of nitrogen, 

 €tc., by the trade value per pound; the same course is 

 adopted with reference to the various forms of phosphoric 

 acid and of potassium oxide. We thus get the values per 

 ton of the several ingredients, and, adding them together, 



