Rotation of Crops 



it receives. For this reason it is said to be a 

 restorative plant. In cereals, on the contrary, 

 the whole is used — the straw as well as the 

 grain. Nothing remains in the ground but 

 the roots, and as they derive almost every- 

 thing from the ground, because of their scanty 

 foliage, they receive much more than they 

 give. They are exhaustive plants. 



So it would be impossible, without going to 

 ruinous expense in manure, to have a crop of 

 cereals every year on the same ground. But 

 what would happen if we were to use the wheat 

 and the potato alternately ? The latter, 

 deriving most of their food from the air, might 

 flourish in the ground that was too poor for 

 the wheat, and their buried tops would restore 

 some of its former fertility to the ground. 

 The wheat might then again be cultivated 

 with success. This practice which consists in 

 growing successively on the same ground 

 plants that do not injure one another and get 

 the best result from the manure expended, is 

 the rotation of which we have already spoken. 

 The object is to diminish the amount of 

 manure required while allowing continuous 

 crops. 



The fundamental principle of rotation con- 

 sists in causing an exhaustive plant to be 



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