26 THE HANDBOOK FOR PRACTICAL FARMERS 



which it is applied, and does not necessarily haTe any connection 

 with the price or trade value. For example, on a soil already 

 well supplied with nitrogen and potash a ton of acid phosphate 

 costing twenty dollars may have the same or a greater value 

 than the same amount of complete fertilizer costing fifty dollars 

 per ton. 



Calculating and comparing trade values. — To calculate the 

 price per unit, the price per ton should be divided by the per cent 

 of plant food contained. Thus, for example, if it is desired to 

 determine , what sixteen per cent acid phosphate, selling at 

 twenty-four dollars per ton, is worth per unit, divide twenty- 

 four dollars by sixteen, which gives one dollar and fifty cents 

 as the price per unit. To determine the price of potash in an 

 0-12-4 fertilizer, selling at thirty-four dollars per ton, first 

 deduct the value of the twelve units of phosphoric acid which, 

 at one dollar and fifty cents, is eighteen dollars. This leaves 

 sixteen dollars as the price of the four units of potash. Dividing 

 sixteen dollars by four, gives four dollars as the price per unit 

 of potash. If, next, it is desired to know the price of nitrogen 

 in a 2-12-4 fertilizer, selling at forty-six dollars per ton, deduct 

 first the value of the twelve units of phosphoric acid and four 

 units of potash, which is thirty-four dollars. This leaves twelve 

 dollars as the price of the two units of nitrogen. Dividing twelve 

 dollars by two, gives six dollars as the price per unit of nitrogen. 



Quantity and kind of fertilizer to use. — The quantity of 

 fertilizer used must be related to the value of the crop treated. 

 The higher the acre value of a crop, the larger the quantity of 

 fertilizer that ma3^ be used profitably. The season when a crop 

 growls influences the need for fertilizers. Grain and ha}^ crops 

 may usually receive an application of two hundred to four hun- 

 dred pounds, potatoes six hundred to one thousand pounds, 

 garden and vegetable crops one thousand to two thousand 

 pounds, and fruits five hundred to eight hundred pounds. 



Crops that mature seed are usually those most benefited by 

 phosphorus. Crops that make a large vegetative growth i'n 

 leaves, roots, and flowers, and are used for those parts, are 

 especially benefited by nitrogen. Potassium is most used in stem 

 and root plants; this element gives stiffness to straw, and is 

 especially beneficial to leguminous crops and to root crops. 



Plants that start growth in early spring or late fall generally 

 are benefited by the addition of a little available fertilizer, 

 especially nitrogen. 



In the absence of knowledge that the soil is well supplied with 



