Soot
This substance is employed in gardening, either as a fertiliser, or to prevent or cure insect ravages, or with all these objects combined. It is, in by far the greater proportion of cases, obtained from chimneys, from the smoke of coal fires. Taken from this source, it usually consists of about 12 per cent. water, 35 to 50 per cent. ash, and the rest volatile substances, which are destroyed by complete combustion. The last-named substances are largely composed of Ammonia; this gives a pungent smell, which is rendered much stronger when quicklime and water are mixed with the Soot. There are also various oily substances, possessed of peculiar smells, and certain acids, formed and driven off by heat during the combustion of coal, that become mixed with the Soot. The ash of Soot contains Calcium, Iron, Magnesium, Potassium, and Sodium, combined variously with Phosphoric and Sulphuric Acids; there is also present a small quantity of Silica and Silicates. The fertilising effect of a top-dressing of Soot is very decided, and seems to be due, in a great degree, to the presence of Sulphate and Chloride of Ammonium; but the other substances may also produce some effect. Soot has been found to greatly benefit Potatoes, when put into the drills. As a remedy against those larvae that lie underground during the day, and crawl up to feed on the plants at night, Soot is especially useful, if laid rather thickly around the stems; it will also stimulate the plants to healthy growth. It is also frequently scattered as a top-dressing, or along the drills, about the time when any crop is liable to visits of the parent insects intent on egg-laying; in such a case, it acts as a preventive of attacks. Soot is also used, instead of hellebore powder, for scattering over plants attacked by larvae (e.g., Sawfly larvae on Currant-bushes), or by perfect insects (e.g., Turnip Flea on Turnips), and gives valuable results when rightly employed; but care must be taken to avoid applying it when the flavour of the crop would be injured.
To cleanse walls from Red Spider, water with which Soot has been mixed till all that can be dissolved from it has been so, is made up with clay till the mixture is of the consistence of thick paint; and then about 1lb. of flowers of sulphur and 2oz. of soft soap are added to each gallon of the compound. To protect the fruit-trees on the walls from the attacks of the mites, this mixture should be applied all over the wall once a year, taking care to close all crevices.