THE PRINCIPLES OF FERTILIZER PRACTICE 483 



profit from the use of the fertilizer depends on the interrela- 

 tion of a number of factors more or less variable from season 

 to season. 



The selection of a suitable fertilizer, as to carriers and com- 

 position, entails, after the need of the crop and soil are de- 

 cided, a careful study of the guarantee. Should the guarantee 

 be such as that just cited, a large amount of information is 

 at hand concerning the forms of the carriers and the availa- 

 bility of the important constituents. This knowledge, prop- 

 erly correlated with the probable needs of the crop and the 

 soil, will determine whether a particular brand should be pur- 

 chased or not. The real question here is not so much the 

 actual quantities of the elements in a ton of the fertilizer, 

 as it is their balance among themselves. The actual pounds of 

 nitrogen, phosphoric acid, or potash applied to the acre can 

 be governed by the rate at which the mixture is added. 



The purchase of high-grade goods is the second important 

 point to be considered. Data collected from practically every 

 State show that the higher the grade of the fertilizer, both as 

 to availability and as to the percentage of the constituents 

 carried, the greater is the amount of nutrients obtained for 

 every dollar expended. ' Avoiding the abnormal war 

 prices, thefollowiBg data from Vermont^ for 1909 seem 

 representative : 



Table XCVIII 





Cost (in Cents) of One Pound of 



Cents' Worth 



OF jt^UTRIENTS 



Mixed Fertilizer 



NH3 



PA 



K,0 



Eeceived for 

 Every Dollar 



Expended 



Low grade , 



Medium grade 



High, grade 



32 

 26 

 23 



7.6 

 6.3 

 5.7 



S,5 

 7.0 

 6.3 



50 

 60 

 67 







* Hills, J. L., Jones, C, H., and Miner, H. L., Commercial Fertilisers; 

 Vt. Agr. Exp. Sta., Bui. 143, pp. 147-149, 1009. 



