" It appears to me a matter of the greatest importance to regulate the application of manure to our fields, so that its constituents may become properly diluted and uniformly distributed amongst a large mass of soil. By ploughing in the manure at once,. it appears to me, this desirable end cannot be reached so perfectly as by allowing the rain to wash in gradually the manure evenly spread on the surface of the field." Among other conclusions regarding the common management of dung-heaps to which Dr. Wicker leads us, are the following : During the fermentation of dung, the phosphate of lime which it contains is rendered more soluble than in fresh manure. In the interior and heated portions of manure-heaps, ammonia is given off; but, on passing into the external and colder layers of dung-heaps, the free ammonia is retained in the heap.
Ammonia is not given off from the surface of well compressed dung heaps, but on turning manure-heaps it is wasted in appreciable quanti ties. Dung-heaps, for this reason, should not be turned more fre quently than absolutely necessary.
If rain is excluded from dungleaps, or little rain falls at a time, the loss in ammonia is trifling, and no saline matters of course are re tuure•1; but if much rain f.rlle, especially if in heavy showers, upon the dung.heep, a serious loss in ammonia, soluble organic matter, phos phate of lime, and wits of potash' is incurred, and the manure becomes rapidly deteriorated in value, whilst at the same time it is diminished in weight.
The worst method of making manure is to produce it by animals kept in open yards, since a large proportion of valuable fertilising matter is wasted in a short time; and after a lapse of 12 months, at least 2-3rde of the substance of the manure is wasted, and only 1.3rd, inferior in quality to an equal weight of fresh dung, is left behind. The most rational plan of keeping manure in heaps appears to be that adopted by Mr. Lawrence, of Cirencester, and described by him at length in Morton's Cyclopedia of Agrieulture;—w•hicla consists essentially in adding each day's store to a narrow heap, and covering it with earth at once, completing the heap es you go.
The great use of liquid manure on light soils is to impregnate them with soluble matter, which being diffused through their substance, supplies nourishment to the roots of plants, wherever they may shoot out. It may be applied to the land at any time before the seed is sown, and soon after, when the blade springs up or the seed begins to, form ; iu short, whenever the plant requires fresh nourishment, or when that which existed in the soil is diminished. Without liquid
manure, the poor ailicions sands of Flanders could never be cultivated, much less produce crops which vie in quantity and quality with those on the best SOBS. The quantity of farm-yard dung, in a very rotten state, which this soil would recinira according to the common system of manuring, could never be produced by all the straw which can be raised upon it in its first state of cultivation. But cattle produce urine, and this produces roots for cattle. The great effect of liquid manure has set the farmers on finding some artificial substitute for the simple urine and diluted dung of cattle. Such substitutes are obtained by mixing all kinds of refuse animal matter with water, and inducing putrefaction. The emptying., of privies from towns is scarcely a sub stitute ; for it is the same as the' liquid from the stables in a more con centrated form ; but the refuse of oil-mills and various manufactures, when diluted and mixed with a portion of putrid urine, soon become assimilated to it. This becomes a branch of trade in those countries where nothing will grow without manure, and is a resource where an increasing population demands the cultivation of inferior soils to supply the necessary increase of food, as well as an increase of produce from those which are naturally fertile.
The increase of manure by the formation of composts is well known in many parts of Britain, and by their means the laud has in many dis tricts being rendered much more productive. The fundamental principle upon which composts have been made, is that of impregnating portions of earth with those parts of the dung of cattle, which, from u-ant of management in the common dunghills, would have been dissipated and lost : and also accelerating or retarding the decomposition of animal and vegetable substances by the addition of earths, such as chalk, marl, clay, and even sand, according to the nature of the soil on which the compost is to be used. All solid manure which is to be ploughed into the ground should contain certain parts already soluble in water, which promote vegetation : while other portions should be in a progressive state, so as to afford a succession of soluble matter by a gradual and slow decomposition.