Notwithstanding some apparently contradictory opinions, it is pretty generally acknowledged by those who have had long experience of its use, that urine and similar animal substances have a more powerful effect on the soil, when they have undergone a certain degree of putre faction, than when they are used in a fresh state, and that this is produced with the least loss of substance when the liquid has been confined in close vaulted cisterns which admit the external air only partially. On light soils this liquid has it most fertilising effect, if it is used frequently in small portions at a time. On vary heavy soils this effect is not so apparent, and for such soils the liquid is accordingly mixed with sand or any light earth before it is applied ; or, instead of using it at once upon the land, it is poured over the litter, which has been collected in a heap or In a yard, after having served for the cattle. This litter, having been deprived of the urine which would otherwise have mixed with it, would rot very slowly and produce a very inferior kind of manure, unless it were moistened, and fermentation were excited by pouring the half-putrefied urine over it. It may be objected that if the urine Is only collected to moisten the straw which has served as litter, it would be as well to let it be mixed at first, without the trouble of pumping it up and the expense of a cistern to hold it. But we shall soon see that there is a very wide difference. In the common mode of collecting farm-yard dung, the straw is very un equally impregnated with animal matter : at one time it will contain a large portion and run rapidly into fermentation ; at another, there will be so little, that it is with difficulty that heat Is excited in it. By separating the urine and litter, the straw will go much further, and can be mixed with the urine at the most advantageous time ; thus it forms a much richer manure in a smaller compass, from not being so much diluted with water. Should there be a deficiency of straw, earth or sand will supply its place, in as far as soaking up the rich juices; for the addition to-the manure from the decomposition of the straw itself is very small in proportion to that which animal juices afford. If the liquid is collected from a stable or a yard where cattle are kept as soon as it is produced, and is carried 6ff into a cistern, there will be a much better and drier bed left for the cattle, especially if the rain be kept off by light shades. When the litter is soiled to a certain degree, it may be removed to a heap in a proper place, where its conversion into rich dung may be effected by the addition of putre fying urine, than which nothing will so soon rot vegetable fibres, if the air be admitted to the heap. The portion which is not wanted for some time may he left to decompose more slowly ; and as the time approaches when it is wanted for the land, it may be managed so as to be in that state which experience has shown to he most effective in the improvement of the crops.
There Is some appearance of certainty and regularity in this mode of making a dunghill, which there scarcely is in the common practice of accumulating straw, dung, and urine without any regularity in a farm-yard, turning it over when the cattle' leave it for the pastures, and carrying so many cart-loads per acre on the land to be manured, without any measure of Its comparative strength. One portion is often almost burnt black, and another appears like the fresh litter of the stables, not being even thoroughly soaked with moisture. It is true that good farmers pay more attention to their dung-heaps, and •endeavour to carry out the manure in a proper state ; but how much more readily would this be accomplished by the help of a large cistern full of the richest animal matter in a state of partial putrefaction.
' In situations where straw bears a high price, it may be doubtful whether a cistern might not permit a considerable profit to be made by the sale of a portion of the straw, without any diminution of the manure required for the farm, since for light soils the liquid might be used alone, and for stiffer soils it might be mixed into a compost with earth, chalk, and any kind of refuse vegetable matter of less value than straw. It was an opinion expressed by a celebrated agriculturist * to the late Mr. Rham, that he considered the use of straw in dung to be merely as a sponge to hold the liquid animal matter in its pores or tubes. In fact, straw or old thatch merely rotten by long exposure to air and moisture is of little or no value as a manure, although it will sometimes produce good potatoes, by rendering a stiff soil pervious and porous ; but, in a light soil, a gallon of urine is worth ten times its weight of rotten straw. This doctrine may appear strange to some agriculturists, but it will bear the test of experiment.
It is well to add here the conclusion to which Dr. Valcker's re searches into the composition and management of yard manure have led him. We extract them in au abridged form from his papers in the 'Journal of the Agricultural Society.' " Perfectly fresh farm-yard manure contains but a small proportion of free ammonia.
" The nitrogen in fresh dung exists principally in the state of insoluble nitrogenised matters.
"The soluble organic and mineral constituents of dung are much more valuable fertilisers than the insoluble. Particular care, therefore, should be bestowed upon the preservation of the liquid excrements of animals, and for the same reason, the manure should be kept in per fectly waterproof pits, of sufficient capacity to render the setting up of dung-heaps in the corner of fields, as much.as It is possible, unneces-ary. Farm-yard manure, even in quite a fresh state, contains phosphate of lime, which is much more soluble than has hitherto been suspected. The urine of the horse, cow, and pig, does not contain any appreciable quantity of phosphate of lime, whilst the dminings of dung-heaps con tain considerable quantities of this valuable fertiliser. The drainings of dung-heaps, partly for this reason, are more valuable than the urine of our domestic animals, and therefore ought to be prevented by all available means from running to waste.
" The most effectual means of preventing loss in fertilising matters is to cart the manure directly an the field whenever circumstances allow this to be done.
" On all soils with a moderate proportion of clay, no fear need be entertained of valuable fertilising substances becoming wasted if the manure cannot be ploughed in at once. Fresh, and even well rotten dung contains very little free ammonia ; and since active fer mentation, and with it the further evalutiou of free ammonia, is stopped by spreading out the manure on the field, valuable volatile manuring matters cannot escape into the air by adopting this plan. As all soils with a moderate proportion of clay possess in a remarkable degree the power of absorbing and retaining manuring matters, none of the saline and soluble organic constituents are thus wasted, even by a heavy fall of rain. It may, indeed, be questioned, whether it is more advisable to plough in the manure at once, or to let it lie for some time on the surface, and so give the rain full opportunity to wash it into the soil.