PROFITS DETERMINE USE OF FERTILIZERS 207 



the one crop to which it is applied. Though it may be good business 

 practice to apply fertilizers to a crop and increase the net profits, 

 yet it is still better practice to accomplish this in such a way as to 

 effect a more permanent improvement of the soil, which will serve 

 to benefit several crops in succeeding seasons. 



Profits Determine Use of Fertilizers. The use of commercial 

 fertilizers depends mainly upon whether or not the value of the 

 increased yields more than offset the cost of the application (Figs. 

 137 and 138). On many soils the use of commercial fertilizers 

 does not pay (Fig. 139). The best returns from fertilizers are 



FIG. 139. Corn stimulated by complete fertilizer applied in the hill (125 pounds per 

 acre). No appreciable difference in yield at harvest time. Soil in good state of fertility. 

 (See page 208.) 



obtained when soils are sufficiently supplied with moisture and 

 organic matter (compare Figs. 140 and 141). 



The cost of fertilizers varies in different sections, depending 

 largely upon the distance from distributing centers. Fertilizers 

 are usually purchased on the unit basis. One per cent of a ton, 

 or twenty pounds, is called a unit. Normal prices for nitrogen 

 have been about three dollars per unit; phosphoric acid (P2O 5 ) 

 from twenty to forty-five cents in rock phosphate, and about one 

 dollar in soluble phosphates; and potash about one dollar to 

 one dollar and forty cents per unit. 



The World War had a decided effect on fertilizer prices. The 

 price paid for nitrogen was six to seven dollars per unit; soluble 



