A judicious rotation, or round of crops, has long been considered, in England, essential to good husbandry: and so it is by skilful farmers in our own country; particularly in the middle States, where clover, so highly important in the rotation, has, for more than thirty years, been rendered wonderfully productive, by the application of plaster of Paris. The most usual course in England has been (excepting on stiff clayey soils) first year turnips, manured and kept clean by hoeing; the second year barley, with clover seed; the third year the clover mown for hay; and its second crop, at wheat seed time, ploughed in, and, where necessary to fill the seams, the ground harrowed, the wheat sown, and then harrowed in. This is called "wheat upon a clover lay."--But by the long and frequent repetition of clover, (that is, once in _four_ years) in their rotations, lands in England became (as they express it) "sick of clover:" and I have been informed that some lands in our middle States, long subjected to the like application of clover, exhibit like symptoms of disease or failure. But Mr. Arbuthnot introduced clover once in _three_ years, without suffering by such more frequent repetition. "He attributed the failure of this plant to shallow and ill-executed ploughing; the result (says Mr. Young) justified his opinion." Mr. Young mentions a lecture he had read to the Board of Agriculture, "on the means by which a farm can be made, by a right proportion of all the products, to support itself, without foreign assistance, in a state of high fertility, a question depending on the quantity or weight of dung resulting from the consumption in litter of a given weight of straw." This lecture I have not seen. But he considers the question as successfully decided, in Mr. Arbuthnot's practice, in the following manner; 134 sheep and 30 lambs were turnip fed, in a pen on a headland, well littered with straw: in six weeks they required nearly six tons of straw [to give them clean and comfortable beds:] and in that time made 40 tons of dung, equal to that brought from London [stable dung it is to be presumed.] So every ton of litter produced near seven tons of dung.--But this weight must have been obtained chiefly by the earth of the headland absorbing the urine, of which, when fed on turnips, sheep make great quantities, and being finally mixed with their dung and litter. This recital reminds me of the recommendation, in my address to this Society, in May, 1818, to carry earth into the barn yard, once in every two weeks, from spring to autumn; adding to every layer of earth a coat of litter. I should then have advised a plentiful spreading of litter, had I not known that our courses of husbandry in Essex yielded very little straw.