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.

Farm-yard manure, 100 Solid excrements of the cow, 125 ” ” ” horse, 73 Liquid ” ” cow, 91 ” ” ” horse, 16 Mixed ” ” cow, 98 ” ” ” horse, 54 ” ” ” sheep, 36 ” ” ” pig, 64 Dry flesh, 3 Pigeons’ dung, 5 Flemish liquid manure, 200 Liquid blood, 15 Dry blood, 4 Feathers, 3 Cow hair, 3 Horn shavings, 3 Dry woollen rags, 2½

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.

Hence the practical farmer sees the reason why no one simple manure can long answer on the same land; and why in all ages and countries the habit of employing mixed manures and artificial composts has been universally diffused.