Animals are among the most essential agents in the maintaining of the fertility of the land. Farm manures are of great value, not only for the plant-food they contain, but for the humus that they contribute and the organisms that they carry.
Composition and Characteristics of Manures (Brooks)
For practical purposes, one will be sufficiently accurate in estimating well-kept barnyard (or cattle) manure to contain one-half of one per cent each of nitrogen and potash, and one-third of one per cent of phosphoric acid. On this basis, a ton of manure would contain 10 lb. each of nitrogen and potash, and 6f lb. of phosphoric acid. A cord of well-preserved manure kept without loss of urine and without exposure to the weather will weigh a little more than three tons. A cord of such manure, therefore, should contain about thirty pounds of nitrogen and potash and twenty pounds of phosphoric acid.
Stable or horse manure.
The manure from horses is generally more valuable than that from the other larger domestic animals, excepting sheep, provided it has been well kept. It is richer in nitrogen, and usually also in phosphoric acid and potash, than the manure of either cattle or hogs. It contains relatively little water, and ferments rapidly.
Experiments at the Cornell Experiment Station showed horse manure to have the following composition: water, 48.69 per cent; nitrogen, 0.49 per cent; phosphoric acid, 0.26 per cent; potash, 0.48 per cent. Plaster was very freely used in this experiment, and this doubtless reduced the percentages, so that the figures are undoubtedly below the average.
Sheep manure is generally accumulated under the animals with sufficient litter to keep the latter dry and clean. Under these conditions, there is commonly no appreciable loss either of urine or of ammonia because of excessive fermentation. The amount of urine voided by sheep is relatively small, and the elements of value in sheep manure ordinarily suffer less loss than is common in the case of other kinds of farm manure. When sheep manure is finally removed from the pens and put into loose piles, as is often the case, in order that it may be worked into suitable mechanical condition to spread, it very rapidly undergoes decomposition, and heats quickly. It is then likely to lose a part of its nitrogen in the form of ammonia. To prevent this, it is well to scatter kainit or land-plaster as the pile is built up. The average of four analyses of sheep manure made at the Massachusetts Experiment Station showed it to contain: water, .2922 per cent ; nitrogen, 1.44 per cent; phosphoric acid, .92 per cent; potash, 1.17 per cent. Sheep manure is now sometimes collected, dried, and ground, and put on the market as sheep guano. In this form it is a concentrated manure, especially valuable for dressing lawns, for use in hothouses, and like purposes.
The manure made from swine undoubtedly varies more widely than that from the other domestic animals, because of the wider variations in the nature of their food and the conditions under which they are kept. The excrements of swine on most farms are not kept by themselves but are mixed with other manures, and this in general would seem to be the better system of management. Hog manure, if kept by itself, is relatively watery, and is usually poor in nitrogen and rich in phosphoric acid. It decomposes slowly, and must be ranked as a cold manure.
Comparison of Manure from Different Animals (Brooks)
Having made separate statements on the qualities and characteristics of the manure from cattle, horses, sheep, and swine, we may now compare these manures in tabular form: —
Composition of fresh excrement of farm quadrupeds. One thousand pounds of fresh dung contain: —