172 ON ROTATION OF CROPS. 



allowed only one year's repose occasionally, and during 

 that season it is repeatedly turned over by the plough ; 

 every part is thus exposed to the atmosphere, whence it 

 absorbs oxygen, and the weeds, being buried by the 

 plough, serve to enrich, instead of exhausting, the land. 



The system of assolemens we owe to those excellent far- 

 mers the Belgians. It is of two descriptions : the first 

 consists in the judicious cultivation of such a succession 

 of crops, that they shall derive benefit instead of injury 

 from each other ; the second is that of raising two crops 

 simultaneously, which shall mutually benefit each other. 

 As we have no precise term to express these processes, I 

 shall take the liberty of using the French word assolement. 



Those of the first description, which our farmers de- 

 nominate a rotation or course of cropping, is particularly 

 adapted to northern climates. 



Emily. And of what description are the crops which 

 ought to be cultivated in rotation ? 



Mrs. B. Before this point can be determined, we must 

 endeavor to solve the problem why one crop is prejudicial 

 to another of the same family ; why two sorts of grain 

 cannot be raised in succession without the latter degene- 

 rating ; whilst leguminous plants succeeding a crop of 

 grain are improved by it. 



Emily. I thought that the first crop, especially if one 

 of grain, which requires so much nourishment, would in- 

 jure the soil for any succeeding crop by exhausting it of 

 nutritive particles. 



Caroline. But since it appears that leguminous plants 

 can follow grain with advantage, it seems evident that 

 these two crops must feed upon different kinds of nourish- 

 ment, and thus the one will not interfere with the other. 



Emily. You forget, Caroline, that plants cannot se- 

 lect their food, but suck up whatever comes within reach 

 of their roots, and is sufficiently minute to find entrance 

 there. All plants must, therefore, feed upon the same 

 nutritive particles. 



Caroline. Then I will suggest another explanation. 

 Perhaps the roots of plants which succeed each other 

 without injury may be of different lengths, and one crop 



946. What is the system of assolemsl 947. For what climates is 

 rotation of crops particularly adapted 1 ? 948. What does Mrs. B. 

 gay must be ascertained before stating what description of crops should be 

 cultivated in rotation 1 ! 949. How does Caroline think this problem 

 may be solved'? 



