ROTATION OF CROPS. 



And farther, crops whose consump- 

 tion returns to the soil a sufiioienl 

 quantity ofmanure, shall be cultivated 

 at intervals sufficient to maintain or 

 increase the fertility of the farm. 



" And, ilh, when land is to be laid 

 down to grass, this shall be done wlien 

 the soil is fertile and clean. 



" These rules may be applied to the 

 plants wliich form the subject of 

 common cultivation in the fields. In 

 this country, the plants chiefly culti- 

 vated on the large scale are, the 

 cereal grasses, chiefly for the farina 

 of their seeds ; certain leguminous 

 plants, as the bean and the pea ; plants 

 cultivated for their fibres, as the flax 

 and hemp ; for their leaves, roots, 

 and tubers, as the turnip, the cab- 

 bagc, and the potato ; and certain 

 leguminous and other plants for for- 

 age or herbage. The plants of these 

 different classes are yet to be descri- 

 bed ; and they are now only referred 

 to with relation to the order in which 

 they may succeed to each other in 

 cultivation. The \st class of these 

 plants consist of the cereal grasses. 

 These are chiefly wheat, Indian corn, 

 barley, oats, and, partially, rye. All 

 these plants are, in an eminent de- 

 gree, exhausters of the farm. They 

 are all suffered to mature their seeds, 

 and are wholly or partially carried 

 away from the farm. Farther, from 

 the manner of tlieir growth and mode 

 of cultivation, they all tend to favour 

 the production of weeds. For these 

 reasons, and on the general principle 

 that plants of the same or similar 

 kinds should not follow in succession, 

 the cereal grasses should nut succeed 

 each other, but should be preceded 

 or followed by some crop which either 

 exhausts the soil less, or admits of a 

 more perfect eradication of weeds. 



" 2d. The leguminous plants culti- 

 vated for their seeds, as the bean and 

 the pea, are ail exhausters of the soil. 

 Tliey ripen their seeds, and the seeds 

 are for the most part carried off the 

 farm. Some physiologists suppose 

 that they are less exhausters of tiie 

 soil tlian the cereal grasses. But the 

 essential diflerence between them, 

 when considered with relation to 



their effect upon the soil, is that, from 

 their growth and ihe manner of cul- 

 tivating them, they are greatly less 

 favourable to the production of weeds 

 than cereal grasses. By their broad- 

 er system of leaves, they tend to stifle 

 the growth of weeds more than the 

 cereal grasses ; and, farther, they ad- 

 mit of tillage during a great part of 

 their growth. This is especially the 

 case with the bean [and maize], 

 which is therefore regarded as a use- 

 ful cleaning crop, and so is cultivated 

 in rotation with the cereal grasses, 

 as a means of preserving the land 

 clean. 



" 3d. Hemp and flax, which are 

 cultivated for their fibres. The ex- 

 haustion of hemp and flax is not great 

 when they produce no seeds. All 

 plants cultivated for their oils are ex- 

 hausters of the soil. They are suf- 

 fered to form and ripen their seeds, 

 and their stems afford no return of 

 manure to the farm. 



"The next class of plants, from the 

 large return of manures which the 

 consumption of them affords, may be 

 regarded as enriching or restorative 

 crops, in contradistinction to the 

 others, which may be termed ex- 

 hausting crops : 



" 1. The turnip, the rape, and other 

 plants of the cabbage genus, cultiva- 

 ted for their roots and leaves, and 

 consumed upon the farm. 



" 2. The potato, the carrot, the 

 parsnip, the beet, and other plants 

 cultivated for their tubers and roots, 

 and consumed upon the farm. 



" 3. The leguminous plants, the 

 clover, the tare, the Incern, and oth- 

 ers, when cut green for forage, and 

 consumed upon the farm. 



" The plants of the latter class, 

 namely, the leguminous, wlien mixed 

 with gramineous plants, as the rye 

 grass, are commonly termed the arti- 

 ficial grasses, but would be more cor- 

 rectly termed the cultivated herbage 

 or forage plants. They are often suf- 

 fered partially to ripen their seeds, 

 ; and are made into hay ; and in this 

 case they follow the general law, ex- 

 ! hausting the soil more than when 

 1 used green. And when the hay crop 



671 



