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.
SECTION III.—OF THE RELATIVE GROWTH OF
THE DIFFERENT ANIMAL MANURES.
The fertilizing power of animal manures, in general, is dependent, like that of the soil itself, upon the happy admixture they contain of a great number, if not of all, those substances which are required by plants in the universal vegetation of the globe. Nothing they contain, therefore, is without its share of influence upon their general effects, yet the amount of nitrogen present in each affords the readiest and most simple criterion by which their agricultural value, compared with that of vegetable matters and with that of each other, can be pretty nearly estimated.
In reference to their relative quantities of nitrogen, therefore, they have been arranged in the following order, the number opposite to each representing the weight in pounds which is equivalent to or would produce the same sensible effect upon the soil as 100 lbs. of farm-yard manure.
It is probable that the numbers in this table do not err very widely from the true relative value of these different manures, in so far as the organic matter they severally contain is concerned. The reader will bear in mind, however,
1. That the most powerful substances in this table, woollen rags, for example,—2½ lbs. of which are equal in virtue to 100 lbs. of farm-yard manure,—may yet shew less immediate sensible effect upon the crop than an equal weight of sheep’s dung, or even of urine. Such dry substances are long in dissolving and decomposing, and continue to evolve fertilizing matter, after the softer and more fluid manures have spent their force. Thus, while farm-yard manure or rape dust will immediately hasten the growth of turnips, woollen rags will come into operation at a later period, and prolong their growth into the autumn.
2. That besides their general relative value, as represented in the above table, each of these substances has a further special value not here exhibited, dependent upon the kind and quantity of saline and other inorganic matter which they severally contain. Thus three of dry flesh are equal to five of pigeons’ dung, in so far as the organic part is concerned; but the latter contains also a considerable quantity of bone-earth and of saline matter scarcely present at all in the former. Hence pigeons’ dung will benefit vegetation in circumstances where dry flesh would in some degree fail. So the liquid excretions contain much important saline matter not present in the solid excretions,—not present either in such substances as horn, wool, and hair,—and, therefore, each must be capable of exercising an influence upon vegetation peculiar to itself.