THE USE OF FERTILIZERS 



217 



cost of the fertilizer decreases after the lowest application, and 

 that for the very heavy application there is an actual loss. 



275. Conditions that influence the effect of fertilizers. — 

 The extent to which fertilizers are utilized by crops depends 



is 



POUHDS OF FLOATS APPLIED PER. X7CRE 



pounos 



800 /200 



OF PLOPT5 APPLIED 



/600 2000 



PER PCR.E 



34W 



Fig. 32. — In the upper diagram the heavy line shows how the yields of 

 corn were increased by graduated applications of phosphoric acid in floats. 

 It will be seen that the increases in yields were proportionately much greater 

 for small applications than for large. 



The lower diagram illustrates the rate at which the cost of the fertilizer 

 approaches and finally passes the value of the product as the size of the appli- 

 cation increases. 



on the presence or absence of certain conditions. The entire 

 amount of any constituent of a fertilizer is never recovered by a 

 crop in any one year. This is a very important consideration 

 in the manuring of land, for under conditions as they fre- 

 quently exist, the use of fertilizers is wasteful and extravagant. 



