CROPS AND SOIL IMPROVEMENT 



tions of fertilizer materials, using them in various 

 quantities. Each manufacturer has given a mix- 

 ture a brand of his own, and confusion reigns. 

 There is no formula for a soil or crop that will 

 remain absolutely the best, even for one particular 

 field. It represents one's judgment of the present 

 need, and is employed subject to change, just as is 

 the prescription of a physician. It is usually only 

 an approach toward the most profitable amount 

 and kind of plant-food that may be supplied. The 

 one important consideration is that no manu- 

 facturer can know the need nearly so well as the 

 intelligent farmer who knows the history of his 

 field and constantly tests its ability. 



A Few Combinations are Safest. It is the 

 best judgment of scientists to-day that greater 

 results would be obtained from the use of com- 

 mercial fertilizers if the number of formulas could 

 be reduced to ten, or even a less number. The 

 satisfactory fertilizers fall into three classes : 



1. The phosphatic fertilizer, carrying phosphoric 

 acid to land that gets its nitrogen from clover or 

 stable manure, and that continues to supply its 

 own potash. Such a fertilizer should have a high 

 content of phosphoric acid in order that the freight 

 charge, per pound of plant-food, may be as low 



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