The Content of Manure.—When the crops of a farm are fed, the manure contains nearly all the plant-food that went originally into the crops. In the case of idle work-horses on a maintenance ration, the manure contains practically all the plant-food. Cows giving milk remove some fertility, and a growing calf or colt may take out 30 per cent. There is some waste beyond control, but when manure is made on tight floors with good bedding, and is drawn to the field fast as made, on the average it carries back to the soil fully four fifths of the plant-food that existed in the feed. Disregarding all cash valuations for the moment, here is an index of value that should be sufficient in itself to encourage the feeding of crops on the farm and the careful saving of the manure. When one can market his crops to animals on the farm at their cash value, and at the same time retain for his fields four fifths of all the fertility, he is like a manufacturer who can use much of his raw material over and over again. The value is in the manure, and full appreciation is lacking only because a majority of farms do not provide for careful saving of its valuable constituents.
Relative Values.—The plant-food content of manure is determined chiefly by the feed. The animals add nothing: they subtract. The kind of animals consuming the feed does not affect materially the value of the manure made from it, if the animals are mature and not giving milk. The manures from the various kinds of animals differ in value per ton because the feeds differ in character and the manure varies in percentage of water. On an average, however, the total annual product of manure from farm animals, per 1000 pounds of live weight, does not vary widely in value. The rich protein feeds given the cow, and the heavy feeding, more than make amends for the fertility that goes into the milk, and her annual product, per 1000 pounds of live weight, may exceed in value that of the horse by 25 per cent. This is likewise true of the pig, figured on the 1000-pound basis, while in the case of the sheep the value, per 1000 pounds of live weight, is near that of the horse.
In the fertile Miami Valley, Ohio.
These variations are not wide enough to have great importance to the livestock farmer. The manure represents to him four fifths of all the fertility that was contained by the feed he gave the various animals. They added no plant-food, and they took away only a fraction that was not large. They converted the crops into a form of plant-food that either is available or can become so quickly enough, and in addition to the nitrogen, phosphoric acid, and potash that would have a high valuation in a commercial fertilizer, there is a body of organic matter that affects the physical condition of the soil favorably. The manure also promotes the multiplication of friendly soil bacteria. Its possibilities are so great that the inference of many farmers that no successful agriculture can be maintained without it is very natural.
Amount of Manure.—Vivian states that the amount of manure that may be made from feed can be determined by multiplying the total weight of dry matter in the feed by 3. This assumes that bedding will be used in sufficient amount to absorb the urine, and that will require material containing one fourth as much dry matter as there is in the feed. When the amount of hay and grain is known, and the dry matter in all succulent feed is estimated, the total product of manure in tons can be arrived at with fair accuracy.
Analysis of Manure.—As has been stated, the content of the manure must depend chiefly upon the character of the feed. We are accustomed to combine feeding stuffs in differing proportions for horses, cows, pigs, and sheep. Van Slyke names the following approximate percentages of plant-food constituents in fresh excrements of farm animals, the solid and liquid being mixed:
| Animal |
Per Cent Nitrogen |
Per Cent Phosphoric Acid |
Per Cent Potash |
|---|---|---|---|
| Horse | 0.70 | 0.25 | 0.55 |
| Cow | 0.60 | 0.15 | 0.45 |
| Pig | 0.50 | 0.35 | 0.40 |
| Sheep | 0.95 | 0.35 | 1.00 |
| Hen | 1.00 | 0.80 | 0.40 |
He estimates that one ton of average mixed stable manure, inclusive of absorbents, contains approximately 10 pounds of nitrogen, 5 pounds of phosphoric acid, and 10 pounds of potash.