Few owners of private gardens have any conception of the large quantity of manure used to produce the great crops in the market-gardens. Henderson says: "It is a grave blunder to attempt to grow vegetable crops without the use of manures of the various kinds. I never yet saw soil of any kind that had borne a crop of vegetables that would produce as good a crop the next season without the use of manure, no matter how 'rich' the soil might be." Horse-manure is best for garden use, and it should be prepared at least six months in advance by turning and breaking up to prevent heating. Hogs will do this work if given an opportunity. The manure-pile with a continued supply of well-rotted manure is an essential part of satisfactory gardening. The pile may be made a kind of compost-heap where sods, rotten vegetables, and fruits, weeds, soapsuds, and even water are thrown; watering at times of turning the pile if the top appears to be dry.
The commercial manures extensively applied east of the Lakes and on the Western coast are not much used in the prairie States.
Aside from the application of well-rotted manure, the use of wood-ashes or one of the potash combinations of the trade seems to give the best results with a system of rotation (383) in which a clover or other legume sod is turned under once in two or three years to give the needed supply of nitrogen and the bacterial action that seems to enliven the soil in a way not fully understood. Slaughterhouse tankage is also useful in the prairie States, as it is rich in nitrogen and phosphoric acid, which are in available form to be taken up by plant-roots. In the West it is the cheapest form in which nitrogen and phosphoric acid can be obtained.
In private gardens, however, in all parts of the Union, stable manure properly composted, with occasional rotation of clover or cow-peas, will give the most satisfactory results on a small scale. But in addition, in the humid belt, it is always in order to use wood-ashes, kainite, or other form of potash, not too expensive, at least once in three years.