COMPOST, in agriculture, denotes a certain kind of mixture designed to assist the soil in the way of vegetation, instead of dung. The requisites for a compost are, 1. That it ought to be cheaper than the quantity of dung required for an equal extent of soil. 2. It ought to be less bulky; and 3. It ought to produce equal effects.
Under the article AGRICULTURE, we have endeavoured to shew, that the true vegetable food consists in reality of the putrid effluvia proceeding from decayed animal and vegetable substances. If this theory is admitted, the hope of making composts as a succedaneum for dung is but very small, unless they are made of putrefied animal and vegetable substances, in which case, unless in very singular circumstances, they will prove much dearer than dung itself. Several attempts, however, have been made by those who had other views concerning the nature of the true vegetable food. An oil-compost is recommended in the Georgical Essays, upon a supposition that the food of vegetables is of an oily nature. It is made as follows: "Take of North-American potash 12lb. Break the salt into small pieces, and put it into a convenient vessel with four gallons of water. Let the mixture stand 48 hours, then add course train oil 14 gallons. In a few days the salt will be dissolved, and the mixture, upon stirring, will become nearly uniform. Take 14 bushels of sand, or 20 of dry mold; upon these pour the above liquid ingredients. Turn this composition frequently over, and in six months it will be fit for use. When the liquid ingredients are put to one or two hogheads water, a liquid compost will be formed, which must be used with a water cart."
This compost, however, the inventor himself owns to be inferior to rotten dung, as indeed may very naturally be supposed; yet in some cases it seems capable of doing service, as will appear from some of the following experiments which we extract from the essays above-mentioned.
Exp. I. By the author of the essays. "I took four pots, no 1, 2, 3, 4. No 1. contained 12lb of barren sand, with 1oz of the sand oil compost. No 2. contained 12lb of sand without any mixture. No 3. had 12lb of sand with half an ounce of slaked lime. No 4. had 12lb of sand with 4oz of the sand oil-compost. In the month of March, I put six grains of wheat into each pot, and during the summer, I occasionally watered the plants with filtrated water. All the time the plants were consuming the farina, I could observe very little difference in their appearance. But after one month's growth, I remarked that no 1. was the best; no 2. the next; no 3. the next; and no 4. much the worst." The same differences were observed in August, when no 1. the best, had five small ears, which contained a few poor grains of wheat.
Exp. II. By the same. "In the month of June, I selected four lands of equal goodness in a field intended for turnips. The soil was a light sand, with a tolerable quantity of vegetable earth amongst it. It was plowed out of sward in November, and had not borne a crop for many years. I shall distinguish my experimental lands by no 1, 2, 3, 4. No 1. was manured with
Compost. with rotten dung; no 2. with oil compost; no 3. with lime; no 4. was left without any dressing. On the 20th of June they were all sown with turnip-feed broad-cast, and during the course of the season were twice hoed. In November I viewed the field, and made the following remarks. No 1. the best; no 2. the next; no 3. the worst; no 4. better than no 3." Here the oil compost appears in a favourable light; but other trials, made with equal accuracy, seem rather to prove, that it is not proper for turnips, barley, or quick growing vegetables. It requires being meliorated by the atmosphere, and therefore is better adapted for winter crops.