In many countries there are other vegetable products, which are required for the food of the inhabitants, or supply the raw materials of manufactures : these must be introduced into the rotations, according to their effect on the soil and the cultivation they require. Indian corn. or maize, aud French beaus, for their seed, are cultivated iu more Noutheni climates as field crops. Potatoes are now an essential product in some districts, and ono which, after :naive, produces the greatest quantity of food for man from a given portion of land. But potatoes require much manure, and cannot profitably be cultivated to a very great extent as a farm produce, nor repeated on the same land, for any length of time, oftener than ouce iu eight or ten years ; they should believer always enter jute the rotation in that portion of the land sa Melt is to be much worked, cleaned, and manured after a crop of corn.
11e have ourselves for many years adopted a rotation without being tied down to any positive rule, which has been suggested by circum stances, and in some measure regulated by our conviction of the truth of the theory we have attempted to elucidate. In a clayey loam on an impervious subsoil, but mostly completely drained, we have bad turnips and swedes on high ridges, tares. mangel-wurzel, potatoes, and a portion of rye to cut up green ; succeeded by barley and oats sown with clover, rye-grass, and other biennial grass seeds. These were mown for hay the first year, and sometimes the second also, but generally depastured one year at least ; then followed beans, and after these wheat. The green crops were put in after repeated aud deep tillage, and with an ample allowance of manure. The whole of the layer was topairessed with peat or coal ashes in the first year, and what manure could be gut or spared was put on the second year before wiuter, when it was ploughed up. All the corn crops were put in upou one shallow ploughing. We have had no reason ro repent of pursuing this course : but we allow that one year only iu clover would probably be more profitable. The land is not sufficiently fertile by nature to bear wheat after the first year of clover, instead of feeding or making it into hay. This would bring it to some of the rotation adopted in rich alluvial soils. It is a rule which should never be transgressed, that after every crop reaped there should be a remnant of manure auflIcient to ensure a good crop the next year ; and that dab should always be in the land, and considered AS stock in trade en capital invested at good interest. By means of judicious rotations and
tillage a much greater quantity of produce may be raised at a certair expense of labour and capital, than by any desultory and mode of cropping. The farmer should find it his own interest td cultivate his land according to the most approved principles, and the landlord should impose only such restriction as will prevent the tenant from injuring himself by diminishing tho produce of his farm.
It is in the relation of crops to manure—to tho need of it for them and the supply of it through them, that the practical man sees the advantage of rotations. There is a need of rotations arising out of mu relations to our labourers who want constant employment—to our Hal stock, which need constant food—to the soil, which will not continue t< produce the same plant perpetually—to the plants we cultivate, whicl grow more luxuriantly in rotation than in constant succession. And the explanation of this last fact has been founded on the ideas that (1' crop. poises' the land for themselves ; (2) that they exhaust the land for thenutelves ; (3) that they improve the ground for their successors Turnip. for instance consumed on the land bring on it more nitro genoua matter than was given them in their manure ; and so the land is enriched by this pMetice and rendered fit for graio, which on the tla r hand mes more nitrogcuous matter than it can in genera naturally obtain.
The tonsils-Mg are our common rotations— Lis the Norfolk rotation-2, the North of England modification of it —3, Mr. Thomas's, of Lidlington, modification of it-4, a common modification of it in Norfulk-5, tho East Lothian 6-field rotation-6, a common modification of it-7, the Whitfield 8-field course-8, Hewitt Davis'e light laud rotation-9, the rotation of the Cottesweld Gloucestershire-10, common in the fens of Lincolushire-11, in clay-lands, East Lothian-12, carse•lands of Scotland-13, clay-lands of Essex. These rotations vary greatly in their manure producing power. By some one cwt. of meat may be made per acre—by others not a quarter of a cwt.—By some therefore there is food per acre for an ox, making 20 tons of dung for every 4 acres, and on others hardly one for every 16 acres.