CHAPTER XVI 



ROTATIONS 



If a farmer raises corn in a certain field one year, and the 

 next year sows the same field in oats, sowing clover 

 with the oats, so that the third year he has clover in the same 

 field, and then in the fourth year he plants the field in corn 

 again and follows it again with the oats and clover, he is rais- 

 ing crops in rotation. A rotation, then, is raising two or more 

 crops in such a way that they follow each other in a definite 

 order. If two crops alternate with each other on the same 

 field, a two-course rotation is said to be followed. When three 

 crops are used it is a three-course rotation, and so on. When 

 a rotation is followed out completely, the farmer has as many 

 fields as he has crops in his rotation, or some multiple of the 

 number. 



The farmer raises crops in rotation in order to get the 

 largest returns from his land. Larger total returns will be 

 obtained from a piece of land when it is rotated in corn, wheat 

 and clover, for example, than if corn or wheat is grown every 

 year on the same piece of ground. 



A properly selected rotation enables the farmer to keep up 

 the fertility of his land. It does this in several ways. In the 

 first place, while all crops use the same kinds of plant food 

 they do not use them in the same amounts. Corn uses nitro- 

 gen, phosphoric acid, and potash, but it does not use so much 



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