1311. General principles for applying lime. The solution of the question whether quicklime ought to be applied to a soil, depends upon the quantity of inert vegetable matter that it contains. The solution of the question, whether marl, mild lime, or powdered limestone ought to be applied, depends upon the quantity of calcareous matter already in the soil. All soils which do not effervesce with acids are unproved by mild lime, and ultimately by quicklime; and sands more than clays. When a soil, deficient in calcareous matter, contains much soluble vegetable manure, the application of quicklime should always be avoided, as it either tends to decompose the soluble matters by uniting to their carbon and oxygen so as to become mild lime, or it combines with the soluble matters, and forms compounds having less attraction for water than the pure vegetable substance. The case is the same with respect to most animal manures; but the operation of the lime is different in different cases, and depends upon the nature of the animal matter. Lime forms a kind of insoluble soap with oily matters, and then gradually decomposes them by separating from them oxygen and carbon. It combines likewise with the animal acids, and assists their decomposition by abstracting carbonaceous matter from them combined with oxygen. According to Chaptal (Chimie appliquee, &c., vol. i. p. 153.), lime forms insoluble composts with almost all animal and vegetable substances that, are soft, and thus destroys their fermentative properties. Such compounds, however, exposed to the continued action of the air, alter in course of time; the lime attracts carbonic acid from the air; and the animal or vegetable matters decompose by degrees, and furnish new products as vegetable nourishment. In this view, lime presents two great advantages for the nutrition of plants; the first, that of attracting nutritious gases from the air; the second, that of prolonging the action and nutritive qualities of organic substances, beyond the term during which they would be retained if these substances were not made to enter into combination with lime. Thus the nutritive qualities of blood, as it exists in the compound of lime and blood known as sugarbaker's scum, are moderated, prolonged, and given out by degrees; blood alone, applied directly to the roots of plants, will destroy them with few or no exceptions.
