CHAPTER VIII.
THE COMPOSITION AND PROPERTIES OF FARM-YARD AND LIQUID MANURES.
In the preceding chapter, a general manure has been defined as one containing all the constituents of the crop to which it is to be applied, in a state fitted for assimilation. This condition is fulfilled only by substances derived from the vegetable and animal kingdoms, and most effectually by a mixture of both. On this account, and also because its properties are such as enable it to act powerfully on the soil, farm-yard manure must always be of the highest importance. It is, in fact, the typical manure, and in proportion as other substances approach it in properties and composition, is their value for general purposes on the farm.
Farm-yard manure is a mixture of the dung and urine of domestic animals, with the straw used as litter; and its value and composition must necessarily depend upon that of these substances, as well as on the proportion in which they are mixed. The dung of animals consists of that part of their food which passes through the intestinal canal without undergoing assimilation; the urine containing the portion which has been assimilated and is again excreted, in consequence of the changes which are proceeding in the tissues of the animal. Their composition is naturally very different, and must be separately considered.
Urine.—Urine consists of a variety of earthy and alkaline salts, and of certain organic substances, generally rich in nitrogen, dissolved in a large quantity of water. That of the different domestic animals has been frequently examined, but the analyses of Fromberg give the most complete view of their manurial value:—
| Horse. | Swine. | Ox. | Goat. | Sheep. | |
| Extractive matter soluble in water | 2·132 | 0·142 | 2·248 | 0·100 | 0·340 |
| Extractive matter soluble in spirit | 2·550 | 0·387 | 1·421 | 0·454 | 3·330 |
| Salts soluble in water | 2·340 | 0·909 | 2·442 | 0·850 | 1·957 |
| Salts insoluble in water | 1·880 | 0·088 | 0·155 | 0·080 | 0·052 |
| Urea | 1·244 | 0·273 | 1·976 | 0·378 | 1·262 |
| Hippuric acid | 1·260 | ... | 0·550 | 0·125 | ... |
| Mucus | 0·005 | 0·005 | 0·007 | 0·006 | 0·025 |
| Water | 88·589 | 98·196 | 91·201 | 98·007 | 92·897 |
| ——— | ——— | ——— | ——— | ——— | |
| 100·000 | 100·000 | 100·000 | 100·000 | 99·863 |
Composition of the Ash of these Urines.
Human urine has been accurately examined by Berzelius, although his estimate of the proportion of urea is generally admitted to be above the average. His analysis gives the following numbers:—