Preservatives.—The best-known common preservatives of manure in storage are gypsum, kainit and acid phosphate.
Gypsum or land plaster holds ammonia, and is thus of the highest value as a preservative. Gypsum must be moist to be effective, and, hence, should be used regularly upon the fresh manure.
Kainit, which is a low-grade sulphate of potash, checks fermentation, and hence prevents loss of ammonia. It contains much salt, and attracts and holds moisture. It should not be used under the feet of animals.
Acid phosphate contains much gypsum, and unites with ammonia that would otherwise escape.
The Geneva (N. Y.) Station recommends the use of one of the following per day:
| Per Horse. | Per Cow. | Per Pig. | Per Sheep. | |
| Pounds. | Pounds. | Ounces. | Ounces. | |
| Gypsum | 1½ | 1¾ | 4½ | 3½ |
| Acid phosphate | 1 | 1⅛ | 3 | 2½ |
| Kainit | 1⅛ | 1¼ | 4 | 3¼ |
The advantage of using kainit and acid phosphate are that they add potash and phosphoric acid respectively, in which barnyard manure is likely to be deficient. In some soils the potash will be preferable; in others, phosphoric acid will do more good.
Value of Manure of Each Kind of Animal.—It has been figured out that the average value of horse manure per year is $27 per animal; cattle, $19; hogs, $12; and sheep, $2. But these are not the only sources of manure on the farm. The hen-house will annually yield manure to the value of 25 to 50 cents per fowl, if intelligently cared for. The outhouse will produce fertility to the amount of $10 to $50 per year, according to the size of the family, the precautions as to loss by leaching, and the care given. The kitchen slops, including the scraps, are worth $10 to $25 per year, if properly composted. The wood ashes have a distinct and high fertilizing value; but not in the hen-house, where they are worse than wasted. And even coal ashes can be turned to account.
Professor Roberts has suggested $250 per year as a conservative estimate of the value of the manure produced during seven winter months on a farm carrying four horses, twenty cows, fifty sheep and ten pigs. The estimated value may be made much higher in cases where farmers are willing to use thought and labor in preparation and preservation of home-made manures.
Solid Manure and Liquid Manure.—The urine is the most valuable portion of the excretion of animals, according to the tables of the agricultural chemists. It is especially rich in nitrogen, and, hence, its strong odor under fermentation. It is also rich in potash. Its place is on the manure heap, not in a ditch leading to a brook. If it collects in quantities beyond the absorbing power of the manure pile, it should go on the compost heap or else be diluted and at once put upon the land.