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favorable conditions. Tf all plants draw from the 

 earth the same elementary principles they do not 

 draw them in the same proportions nor in the same 

 combinations, and their regular succession allows 

 each in its turn to draw the nourishment best fitted 

 for it. Every one knows, without it being neces- 

 sary for me to explain, the little- advantage to be 

 gained by cultivating the same plants in the same 

 fields for several years in succession : the land soon 

 loses all the substance required by the plant and 

 the crops gradually grow less and less. It can 

 hardly be objected that in uncultivated lands we see 

 indefinitely reproduced, with equal strength of vege- 

 tation, plants spontaneously produced, for we can 

 find in their very diversity a simultaneous rotation 

 which prevents the destruction of the equilibrium 

 of the soil. In a good system of rotation, care must 

 be taken to take a natural order, that is to say 

 the preceding crop prepares and gives way to the 

 succeding one. 



For example beets require a clean, mellow, and 

 deep soil : to have clean soil, for any given year, a 

 plant must be cultivated the preceding year, which 

 by its vigorous growth has choked the greater part 

 of the weeds or which has allowed them to be des- 

 troyed by being cut before their seed has arrived at 

 maturity. 



A rotation of three or four years is often followed. 



In Europe, I have often observed the following 

 four year system. 



