But where upland marle, or even clay, can be had, for the purpose of forming compost manures with the barn dung and the addition of some lime, as is described under manures, &c. we should advise to the rotation first described, or something similar, in which the root crops should form a prominent part; and in such case, let the manure be plentifully applied to the drilled crops. At first, perhaps, some of the crops would not be so abundant; but under this management the soil would be constantly improving, and of course the crops increasing. At first, perhaps, rye should be substituted for the wheat crop, but each addition to the soil of the caluminous and calcarious matter, of which the compost is principally composed, would render the land better adapted for grain crops of every description.
It is a matter of the first importance to the cultivator to possess an adequate knowledge of the different substances which may be used with advantage for fertilizing his land, of the different soils to which such substances are best adapted, of the proper quantities to be used, and of the most advantageous time and manner of their application. There is but little even of the richest earths that will not become exhausted with constant cropping without manure; and soils are seldom so sterile, but that with a proper application of suitable manures to them, they may be made the residence of plenty.
Manures are of different kinds: of animal, of vegetable, of fossil, and of mixed; of each of which notice will be taken in their order.
The flesh of animals is an excellent manure for all soils, and is used to a considerable extent on the sea coast, where fish are caught in plenty. It is believed that flesh is used to most advantage in composts, and the same may be observed with more certainty in regard to the use of the blood. The shavings of the horney substances of animals, have very desirable effects as a manure, in dry soil, by enduing such with a greater power to retain moisture: and the same may also be observed of the hair and wool. The bones, when calcined, are also valuable, as they are principally phosphate of lime. The miasma, produced by the putrefaction of the flesh and blood of animals, is also food for plants, or at least its presence assists their growth. The urine is a fertilizer principally by reason of the salt it contains, and probably also by its producing miasma.
When animals die, it is usual to let them lie above ground, to the annoyance of the public; but, if covered with earth, this together with the flesh, &c. of the animal, would be converted into good manure.
Of vegetable substances, it may be generally observed, that almost every sort of vegetable, not of woody texture, buried in the soil while green, is more or less efficacious as a manure; and that many sorts of these, when turned under where they grew, and while in a green state, will add much more fertility to the soil than their growth extracted from it; but that the same growth, when suffered to ripen on the ground, and then turned under, after the exhaustion of its juices, will not generally repay the soil the nutriment it extracted from it while growing. It would seem that the ripening of plants is the principal cause of the exhaustion of soils, and, for this reason, green dressings, that is, ploughing of green crops under, has been found advantageous in enriching lands. Where green dressings are resorted to, as a manure, such growth should be selected for the purpose as are cheap in the article of seed, and at the same time quick and bulky in their growths. Buckwheat has been much used for the purpose, though perhaps some other plants should be preferred. The growth should be turned under when in blossom; and, in order that this be done effectually, it should be laid prostrate, by running the roller over it, in the same direction in which the plough is to follow; after which, the ground should not be stirred again till this manure has sufficiently rotted. Generally, we think it would be most advisable to sow on the lay or furrow, by which the green crop is turned under.
There may be some instances where manuring with green dressings may be advisable, particularly where it can be done without preventing the growth of any intervening crop: Where this is not practicable, we should hardly advise to this method of manuring, unless in cases where other manures were not to be obtained. One case we will however mention, where a green dressing might be given to advantage. Suppose, for instance, a crop of rye, oats, or barley, harvested, and the ground cleared of the crop by the 20th of July; in that case, let the stubble be immediately turned under, and the ground harrowed in with buckwheat; by the 20th of September this growth would be fit to be turned under, when a crop of wheat might be sown on the lay. It should be understood, that rye is one of the best crops to precede a crop of wheat, or to follow it. In the same manner, therefore, the crop for a green dressing may be raised in the wheat stubble turned under, and the green crop turned under for a crop of rye.
But the contents of the barn-yard, and the excrements of cattle, are the principal sources of manure of the vegetable kind; and of these it is necessary to treat particularly, as well of the qualities of the different sorts, as of their most advantageous applications to soils. The sorts of dung or excrement to be noticed, are those of horses, neat cattle, sheep, and swine. The dung of swine is most valuable, where properly applied; that of sheep is the next; that of cows ranges in the third degree, and that of horses in the fourth. The dung of the latter, if suffered to lie in a heap till it becomes thoroughly heated, assumes a white, or mouldy colour, and is then of but little value. It is of a warm nature, and is best adapted for being well buried in moist or clayey soils; cow dung on the contrary, is most suitable for dry soils; sheep dung answers best on the soils for which that of horses is best suited, but is very valuable for almost any soil. Hog dung should only be applied to dry arable lands, and is most powerful in those of a sandy or gravelly nature. Dung, of all sorts, loses much of its valuable qualities by exposure to frequent rains, particularly when lying at but little depth over a considerable surface. Its good qualities are best preserved by lying in large heaps, and if under cover so much the better. The stercorary is the most effectual method for preserving barn dung, and it is believed that every farmer will find his money well expended in the erection of this receptacle for the contents of that part of his barn-yard, which is not used in the spring. The stercorary may serve for a sheep fold during winter, and will thus answer a two fold purpose. It may be, for instance, 40 feet in length, 16 in breadth, and of suitable height. The floor is to be made of a layer of clay, with the surface smoothly paved with small stones, and highest in the middle, so that the juices of the dung may run off to the sides, where a gutter receives this liquid, and carried it into a reservoir, sunk at one end, into which a pump is to be fixed to raise the liquid and throw it back over the heap. The floor, gutter, and reservoir, are on a plan similar to those of a cider press. The liquid that runs from the heap is the most valuable part, and should never be lost: this plan is therefore calculated to preserve it; and, for the purpose of absorbing the whole of it, any dry vegetable matter, or rich earth, may be laid over the heap, and this liquid thrown on that, which will serve to convert the whole into good manure. The juices and the soluble and gaseous parts of the excrements of cattle, together with the stale, are what principally affords nutriment for growing plants; and every means by which these can be saved, by their being absorbed in other substances, of rich earthy or vegetable matter, would seem to be well worthy of attention. We will next designate what is usually considered the methods most proper for the application of dung.
Where lands are in grasses of the fibrous rooted kinds, it is the generally received opinion of the best cultivators, that barn dung, as well as every other kind, should be applied as a top dressing, that is, by spreading it on the surface; but that for tap rooted grasses, or those whose roots extend deeply, as well as for all grain and root crops, this manure should be buried in the soil, at such depths as are best suited to the nature of the roots of the plants to be cultivated. The operation of barn dung, and of all vegetable and animal substances used in manure, seems to be this: If laid at a certain depth beneath the surface of the soil, in the progress of their decomposition their soluble parts pass into the form of gas, or vapour, and of course rise to the surface, and in their ascent are more or less absorbed by the roots of the plants; on the contrary, if these manures be laid on the surface, these soluble parts, in the progress of decomposition, never become aeriform, but are washed downwards, in their liquid state, where they are in like manner absorbed by the roots of the plants. This is probably as correct an explanation as can be given of the effect of these manures. It is well known, that ground long used as a graveyard, becomes very fertile, notwithstanding the substances which are the cause of such fertility, are laid at a very great depth.
It has been held by some English writers that barn dung should be well rotted previous to its application as a manure, but this opinion is rejected by Sir Humphrey Davy, one of the most scientific agriculturists of Great Britain, and also by Arthur Young, Esq. Mr. Davy contends that this manure may in most instances be as well applied fresh as in any other way, by its being laid at a proper depth beneath the surface, and that in scarcely any instance it is advisable that it should undergo more than the first stage of decomposition before it is used. When well rotted it is, however, more efficacious for a single crop, but its use is of much shorter duration. It seems, also, to be generally agreed that using this manure for drill crops, burying it at a good depth, and raising the plants over the dung thus buried, is the best possible way in which it can be used. We lately saw an account published of upwards of 100 bushels of Indian corn to the acre being raised by this mode of culture. The success of Mr. Cobbett, and others, in raising great crops of ruta baga by this method of using this manure, seems to demonstrate its utility, if evidence was wanting further than what appears in English publications on the subject.