Use of Preservatives.--The use of land-plaster in stables helps to prevent loss of the nitrogen-content through fermentation. Its value does not lie chiefly in physical action as an absorbent, but the beneficial results come through chemical action. The volatile part of the manure is changed into a more stable form. In recent years this preservative has fallen somewhat into disuse, as acid phosphate contains like material and also supplies phosphoric acid to the manure. The phosphoric acid content of stable manure is too low for all soils, and the reenforcement by means of acid phosphate would be good practice even if there were no preservative effect. The use of fifty pounds of acid phosphate to each ton of manure will assist materially in preserving the nitrogen, and the gain in phosphoric acid will repay all the cost. It should be used daily on the moist manure, as made in the stable, and preferably just before bedding is added, so that the phosphate will not come into direct contact with the feet of the animals. Some stockmen prefer the use of acid phosphate and kainit mixed half-and-half. The latter is a carrier of potash, and is a preservative of nitrogen. The use of ground rock-phosphate in stables is coming into use in some localities, chiefly through the recommendation that it be mixed with manure to secure availability of its own plant-food. It is not a preservative except in so far as it acts physically as an absorbent. It should not displace acid phosphate in stables, the preservation of nitrogen in the manure being the vital matter. Spreading as Made.--When farm conditions make it feasible to draw and spread manure fast as made, the danger of heavy loss in storing is escaped. There is evidence that no appreciable escape of fertility occurs when manure is spread on land that is not covered with ice. The phosphoric acid and potash are minerals, and leach into the soil. The nitrogen does not change into a gas in any appreciable amount when spread over the surface, and it likewise leaches into the soil. There are soils in which the decay of the organic matter would have a more beneficial effect than the rotting upon the surface, it may be, but the mulching effect of the manure is valuable. There should be no doubt that the loss from manure is kept to a minimum when it goes directly to the soil. In some latitudes the snow and ice oftentimes prevent spreading, or make it inadvisable, and in many farm schemes it is desirable to hold manure for special fields and crops. Some means of storing manure must be provided in these instances.