THE YOUNG FARMER 



23 bushels; and hay 4,190 pounds per acre. 

 In the first instance the value of the pro- 

 ducts has been $15.75 an acre > while in the 

 other case it has been $22.90 an acre. 



Having worked out a cropping system 

 that gives the proper yearly production of 

 several crops desired, the next question to 

 decide is how this cropping system and the 

 disposition of the crops is going to affect 

 the fertility of the soil. From a financial or 

 economic point of view the most important 

 soil element is nitrogen. First, because it 

 costs from 18 to 20 cents a pound, while 

 phosphoric acid can be purchased at five 

 cents, potash at four cents ; and, second, be- 

 cause of the readiness with which nitro- 

 gen may disappear from the soil under im- 

 proper management, either through nitrifi- 

 cation and leaching or by denitrification and 

 passing back into the air. 



Assuming a given type of management, 

 the question is, How much of the required 

 nitrogen will be obtained from the legumes 

 in the cropping system, how much from the 

 manure, and how much must be purchased 

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