PARING AND BURNING. This operation consists in cutting a thin slice from the surface of land which is overgrown with grass, fern, or any other plants which form a sward by the matting together of their roots. The sods are allowed to dry in the sun to a certain degree, after which they are arranged in heaps, and burnt slowly, without flame or violent heat. The result is a mixture of burnt earth, charred vegetable fibre, and the ashes of that part which is entirely consumed.
The object of this operation is twofold : first, to kill insects and destroy useless or noxious weeds completely ; and secondly, to obtain a powerful manure, impregnated with alkaline salts and carbonaceous matter, which experience has shown to be a very powerful promoter of vegetation.
The instruments by which this is effected are, either a common plough with a very flat share, which may be used when the surface is very level without being encumbered with stones or large roots, as in low moist meadows, or in most other cases a paring-iron used by hand. Instead of the common plough, Snowden's or Woofe's paring plough (Hancock, Gloucester) may be used. It is a very effective tool—self cleaning in its operation—and capable of cutting a thinner slice than can be separated by the common plough. The hand•parer is a most cumbrous tool, and in its use the power of the workman is most wastefully exerted. The crossbar of the instrument is held with both hands ; and the upper parts of the thighs, being protected by two small slips of board, push the instrument into the ground, so as to cut a alio) of the required thickness, which is then turned over by moving the cross handle. The labour is severe, and a good workman can scarcely pare more than one-sixth of an acre in a day. The price of this work is from 158. to 25s. per acre, according to the price of labour. The drying, burning, and spreading of the ashes are contracted for at from 108. to 158. more : thus the whole cost is from 258. to 21. per acre. In France it is done by a cub, which is like a shipwright's adze, and the operation is called Ecutier.
Paring and burning the surface is an almost invariable preliminary In the converting of waste lands to tillage; and where these lands are in a state of nature, overrun with wild plants which cannot be easily brought to decay by simply burying them in the ground, burning is the readiest and most effectual mode of destroying them. In this
Case the practice is universally recommended and approved of.
But it is not only in the reclaiming of waste lands, and bringing them into cultivation,that paring and burning the surface is practised. The fertility produced by the ashes, which is proved by the luxuriance of the vegetation in the first crop, has induced many to repeat this process so often, as materially to exhaust the soil, and induce partial sterility. Hence the practice has been recommended on tho one hand, and strongly reprobated on the other.
When we come to apply to the subject the test of experience, and reason correctly on the facts which are presented to us by the abetters of the practice and its adversaries, we shall find that the advantages and disadvantages arise chiefly from the circumstances under which the operation is carried on. But it may be necessary to an impartial examination of the subject, to inquire into the changes produced on the substances subjected to the process of burning, when it is done with due precautions.
In burning vegetable matter in an open fire, the whole of the carbon is converted into carbonic acid and flies offi leaving only some light ashes containing the earthy matter and the salts which the fire could not dissipate. These are no doubt very powerful agents in promoting vegetation, when they are added to any soil : but they are obtained at a very great expense of vegetable matter, which by its decomposition in the earth, might also have afforded food for vegetation. If the earth which is burnt with the sods is of a cold clayey nature, the fire will change it into a kind of sand, or brick dust, which is insoluble in water, and corrects the too great tenacity of clays, by converting them more or less into looms. This in ao well known, that clay is often dug out of the subsoil to be partially burnt. But in addition to the many mechanical effects of heat on clay, there are certain chemical results of great advantage to fertility. When not burned to excess the alkaline ingredients of clays become more soluble when they are exposed to heat, and no doubt some of the beneficial effects of clay burning are due to the greater quantity of soluble alkaline matter which is then made available : and on stiff clay soiLs therefore there is a double advantage in paring and burning, that of the vegetable ashes and of the burnt clay.