Section Ii.—of Digested Animal Manures.

Practical men have long been of opinion that the digestion of food, either animal or vegetable,—the passing of it through the bodies of animals,—enriches its fertilizing power, weight for weight, when added to the land. Hence, in causing animals to eat up as much of the vegetable productions of the farm as possible, it is supposed that not only is so much food saved, but that the value of the remainder in fertilizing the land is greatly increased. In a subsequent section we shall see how far theory serves to throw light upon these opinions. (See Section IV., p. 182 to 186.)

I. LIQUID EXCRETIONS.

The digested animal substances usually employed as manures are, the urine of the cow and the sheep, the solid excrements of the horse, the cow, the sheep, and the pig, the droppings of pigeons and other birds, and night-soil. The liquid manures act chiefly through the saline substances they hold in solution, while the solid manures contain also insoluble matters, which decay slowly in the soil, and there become useful only after a time. The former, therefore, will influence vegetation more powerfully at first; the action of the latter will be less evident, but will continue to operate for a much longer period.

Urine.—Human urine consists, in 1000 parts, of

Water, 932 Urea, and other organic matters containing nitrogen, 49 Phosphates of ammonia, lime, soda, and magnesia, 6 Sulphates of soda and ammonia, 7 Sal ammoniac and common salt, 6 ---- 1000

A thousand pounds of urine therefore contain 68 lbs. of dry fertilizing matter of the richest quality, worth, at the present rate of selling artificial manures in this country, at least 20s. a cwt. As each person voids almost 1000 lb. of urine in a year, the national waste incurred in this form amounts, at the above valuation, to 12s. a head. And if five tons of farm-yard manure per acre, added year by year, will keep a farm in good heart, four cwt. of the solid matter of urine would probably have an equal effect; or the urine alone discharged into the rivers by a population of 10,000 inhabitants would supply manure to a farm of 1500 acres, yielding a return of 4500 quarters of corn or an equivalent produce of other crops.

The urine of the cow is said to contain less water than that of man, though of course much must depend upon the kind of food with which it is fed. Reckoning, then, the large quantity of liquid manure that is yielded by the cow (2000 or 3000 gallons a year), we may safely estimate the solid matter given off by a healthy animal in this form in twelve months at 1200 to 1500 pounds weight, worth, if it were in the dry state, from £10 to £12 sterling. In the liquid state, the urine of one cow collected and preserved as it is in Flanders, is valued in that country at about £2 a year. Any practical farmer may calculate for himself, therefore, how much real wealth, taking it even at the Flemish value, is lost in his own farm-yard—how much of the natural means of reproductive industry passes into his drains or evaporates into the air.

This liquid manure is invaluable, when collected in tanks, for watering the manure and compost heaps, and thus hastening their decomposition; but great part of it may also be sprinkled directly upon the fields of grass and upon the young corn, with the best effects. It must, however, be permitted to stand till fermentation commences, and afterwards diluted with a considerable quantity of water, before it will be in the best condition for laying on the land.

Urate.—In order to obtain the virtues of animal urine in a concentrated form, the custom has been adopted of mixing burnt gypsum with it, in the proportion of 10 lbs. to every 7 gallons, allowing the mixture, occasionally stirred, to stand some time, pouring off the liquid, and drying and crushing the gypsum. This is sold by manure manufacturers under the name of urate. It never can possess, however, the virtues of the urine, since it does not contain the soluble saline substances, which the gypsum does not carry down with it. Except the gypsum, indeed, 100 lbs. of urate contain no greater weight of saline and organic matter than 10 gallons of urine. If it be true, then, as the manufacturers state, that 3 or 4 cwt. of urate are sufficient manure for an acre, the practical farmer will, I hope, draw the conclusion,—not that it is well worth his while to venture his money in trying a portion of it upon a piece of his land,—but that a far more promising adventure will be to go to some expense in saving his own liquid manure, and, after mixing it with burned gypsum, to lay it abundantly upon all his fields.

II. SOLID EXCRETIONS.

Cow and Horse Dung.—So much of the saline, nutritive, and soluble organic matters from the cow pass off in the liquid form, that cow dung is correctly called cold, since it does not readily heat and run into fermentation. Mixed with other manures, however, or well diffused through the soil, it aids materially in promoting vegetation. The horse being fed generally on less liquid food, and discharging less urine, yields a hotter and richer dung, which, however, answers best also when mixed with other varieties. The dung of the swine is soft and cold, like that of the cow, containing, like it, at least 75 per cent. of water. As this animal lives on more varied food than any other reared for the use of man, the manure obtained from it is also very variable in quality. Applied alone, as a manure to roots, it is said to give them an unpleasant taste, and even to injure the flavour of tobacco. It answers best for hemp, and, it is said, also for hops; but, mixed with other manures, it may be applied to any crop.

Night-soil is probably the most valuable, and yet, in Europe at least, the most disliked and neglected of all the solid animal manures. It varies no doubt in richness with the food of the inhabitants of each district,—chiefly with the quantity of animal food they consume,—but when dry, no other solid manure, weight for weight, can probably be compared with it in general efficacy. It contains much soluble and saline matter, and as it is made up from the constituents of the food we eat, of course it contains most of those elementary substances which are necessary to the growth of the plants on which we principally live.

Attempts have been made to dry this manure also, so as to render it more portable,—to destroy its unpleasant smell, so as to reconcile practical men to a more general use of it,—and by certain chemical additions, to prevent the waste of ammonia and other volatile substances, which are apt to escape and be lost when this and other powerful animal manures begin to putrify through decay. In Paris, Berlin, and other large cities, the night-soil, dried first in the air with or without a mixture of gypsum or lime, then upon drying plates, and finally in stoves, is sold under the name of poudrette, and is extensively exported in casks to various parts of the country. In London also it is dried with various mixtures, while in others of our large towns an animalized charcoal is prepared by mixing and drying night-soil with gypsum and ordinary wood charcoal in fine powder.

The half-burned peat above described (p. 80,) would answer well for such a purpose, while few simple and easily attainable substances would make a better compost with night-soil, and more thoroughly preserve its virtues, than half-dry peat or rich vegetable soil, mixed with more or less marl or gypsum. It is impossible to estimate the proportion of waste which this valuable manure undergoes by being allowed to ferment, without mixture, in the open air.

Taffo.—In China it is kneaded into cakes with clay, which are dried in the air, and, under the name of taffo, form an important article of export from all the large cities of the empire.

Pigeons’ Dung.—The dung of all birds is found to possess eminent fertilizing virtues. Some varieties are stronger than others, or more immediate in their action, and all are improved for the use of the farmer by being some time kept, either alone or in compost. In Flanders the manure of one hundred pigeons is considered worth 20s. a year for agricultural purposes.

Guano is the name given by the natives of Peru to the dung of sea-fowl, which in former periods used to be deposited in vast quantities on the rocky shores and isles of the Peruvian coast. The numerous shipping of modern times has disturbed and driven away many of the sea-fowl, so that comparatively little of their recent droppings is now preserved or collected. Ancient heaps of it, however, still exist in many places, more or less covered up with drifted sand, and also more or less decomposed. These are now largely excavated for exportation, not only to different parts of the coast of Peru, as seems to have been the case from the most remote periods, but also to Europe, and especially to England. It is at present sold at 20s. a cwt. in this country, and is capable of entirely replacing farm-yard dung,—that is to say, turnips may be manured successfully with guano alone;—but it has not yet been satisfactorily determined that the English farmer can afford to use it in this way to any extent, at the price now asked for it.

The dung of birds possesses the united virtues of both the liquid and solid excretions of other animals. It contains every part of the food of the bird, with the exception of what is absolutely necessary for the support and for the right discharge of the functions of its own body. It is thus fitted, therefore, to return to the plant a greater number of those substances on which plants live, than either the solid or the fluid excrements of other animals; in other words, to be more nourishing to vegetable growth.