SUCCESSION OF CROPS. 121 



crops upon the same soil, of causing different vegetables 

 iQ succeed one another, and of understanding the effect 

 of each upon the soil, that can alone establish that good 

 order of succession which constitutes cropping. 



A good system of cropping is, in my opinion, the best 

 guarantee of success that the farmer can have ; without 

 this, all is vague, uncertain, and hazardous. In order to 

 establish this good system of cropping, a degree of knowl- 

 edge is necessary, which unhappily is wanting to the 

 greater part of our practical farmers. I shall here state 

 certain facts and principles, which may serve as guides in 

 this important branch of agriculture. 



More extensive information upon this subject may be 

 found in the excellent works of Messrs. Yvart and Pictet.* 



Principle 1. All plants exhaust the soil. 



Plants are supported by the earth, the juices, with which 

 this is impregnated forming their principal aliment. Water 

 serves as the vehicle for conveying these juices into the 

 organs, or presenting them to the suckers of the roots by 

 which they are absorbed ; thu-s the progress of vegetation 

 tends constantly to impoverish the soil, and if the nutritive 

 juices in it be not renewed, it will at length become per- 

 fectly barren. 



A soil well furnished with manure may support several 

 successive crops, but each one will be inferior to the pre- 

 ceding, till the earth is completely exhausted. 



Principle 2. All plants do not exhaust the soil equally. 



Plants are nourished by air, water, and the juices con- 

 tained in the soil ; but the different kinds of plants do not 

 require the same kinds of nourishment in equal degrees. 

 There are some that require to have their roots constantly 

 in water ; others are best suited with dry soils ; and there 

 are those again, that prosper only in the best and most 

 richly manured land. 



The grains and the greater part of the grasses push up 

 long stalks, in which the fibrous principle predominates; 

 these are garnished at the base by leaves, the dry texture 

 and ' small surface of which do not permit them to absorb 

 much either of air or water ; the principal nourishment is 

 absorbed from the ground by their roots ; their stalks fur- 

 nish little or no food for animals ; so that these plants 



* " Cours complet d' Agriculture," articles AssoleTtieiU et Succession 

 de Ctdiure, par Yvart. — " Traite de Assolemens," par Ch. Pictet. 

 11 



