SECT. VI.

PREPARATION OF THE SOIL, FOR OPEN DISPOSITIONS OF TREES, AND CLOSE PLANTATIONS.

HAVING sufficiently illustrated the New Theory, suggested for Transplantation, the first branch of practice, that claims attention, is the Preparation of the Soil.

The substances which constitute Soils, as Sir H. Davy states, are certain compounds of the earths, silica, lime, alumina, magnesia, and of oxides of iron and manganesum; also animal and vegetable matters in a decomposing state; and saline, acid, or alkaline combinations.* Soils afford to plants a fixed abode, and the medium only of their nourishment. Earths, exclusively of organized matter and water, as the best phytologists admit, are of no other use to woody plants, than to fix them in the ground, and support them: They act merely as mechanical, or as chemical agents: But earth and organic matter united constitute what is pro

* Elements of Agricultural Chemistry.

perly called Soils, and furnish, to plants, at once support and nourishment. The true food of plants, as the same instructive writer observes, is water and decomposing organic matter. The earthy particles are useful in retaining the water, so as to supply it, in due proportions, to the roots of vegetables; and they likewise act, in producing a proper distribution of the animal or vegetable matter. When equally mixed with it, they prevent it from too rapid a decomposition; and they also supply the soluble parts in their due proportions.

Kirwan, in his Geological Essays, has shown, that the fertility of a soil, in a great measure, depends on its capacity to retain water. The The power of the soil to absorb water, by cohesive attraction, depends, in a considerable degree, on the division of its parts. The more these are divided, the greater their absorbent power. Hence the great importance of friability or looseness of texture; so that moisture may have free access to the fibres of the roots, that heat may be readily conveyed to them, and that evaporation may proceed without obstruction. These benefits are usually attained by the presence of sand. As alumina possesses, in an eminent degree, all the powers of adhesiveness, and silex those of friability, it is obvious, that a mixture of those earths, in suitable proportions, would furnish everything that could be wanted in the most perfect soil. In a soil so constituted,

water would be presented to the roots by capillary attraction. It would be suspended in it, says Grisenthwaite, in the same way as in a sponge, that is, in a state not of aggregation, but of minute division, so that every part might be moist, but not wet.* Hence the best soil, whether for wood or agricultural crops, obviously is one that is at once loose and deep, containing the most alumina and carbonate of lime, so as to act with the greatest chemical energy, in the preservation of manures.†

Trees, far more than agricultural crops, require depth of Soil, to raise them to perfection: The effect of climate appears much less necessary, in giving them their greatest magnitude. Accordingly, notwithstanding the insularity of our situation, which naturally tends to the equalization of climates, little Park timber is found in Scotland, or the north of England, approaching, in size and grandeur, to the great Trees in the midland and southern counties, owing probably to the superior soil, which exists in the latter districts. these the Swilcar, Shelton, Chandos, and Fredville Oaks, the Tortworth, Burleigh, and Cobham Chesnuts, the Chipstead and Tutbury Elms, the Woburn Ash, the Knowle Beech, and the Cobham Lime and Sycamore, are eminent examples, as may

*New Theory of Agriculture.

+ NOTE I.

Of

be seen in Mr Sturt's late elegant delineations.* A more powerful delineator than Sturt says, of the King's Oak at Blenheim, that," although scathed and gnarled in its branches, the immense trunk still showed, to what gigantic size the Monarch of the Forest can attain, in the groves of merry England." As it appears plain, from these, and other instances, both in the north and south, that the size of wood will be mainly in proportion to the depth of the Soil on which it grows, it should be the chief study of the planter, to promote that capital object. It is a sound maxim as old as Theophrastus, and repeated by Columella and Pliny, as familiar to the Roman husbandman, to transfer no Tree to a worse soil than that, in which it had previously stood : And whatever in this respect holds true of young plants, must, à fortiori, hold more decidedly true of large subjects, such as are intended for Removal. If, in Transplanting, we must often encrease the cold, and other circumstances adverse to Trees, it becomes us the more diligently to study, that the Soil be rendered as rich and deep as possible, in order, in some sort, to counterbalance those disadvantages.

There are few persons so happily situated, as to

See Sturt's elegant Portraits of British Forest Trees, with respectable letter-press descriptions. Lond. 1826.

Sir Walter Scott, Woodstock, Vol. I. p. 68.
NOTE II.

be able to command much animal or vegetable manure, for the use of Trees. Such artificial modes of enrichment or improvement must therefore be resorted to, as science or experience have pointed out. By following such guides, we may often learn so to alter the constituent parts of Soils, as to encrease their fertility, by the addition of ingredients, in which they are deficient, and, in some cases, by the subtraction of such, as too copiously abound in them; or else, by effecting chemical changes of some constituent part by incine ration, or by the application of mineral manures. Soils, considered as agents of vegetable culture, are subjected to operations, which effect changes on them, either mechanically or chemically. Of the former description there are none so important for the use of Trees, as Deepening and Pulverizing. Deepening can be executed with effect, only by trenching or double-digging (for the plough can do little in such a business), and pulverizing is naturally combined with that process. The depth of pulverization, as Sir H. Davy well observes, must depend on the nature of the soil and subsoil. In rich clayey Soils, it can scarcely be too deep; and even in sands, unless the subsoil contain some principle noxious to vegetables, deep comminution should be practised. When the roots are deep, they are less liable to be injured by excessive rain, or excessive drought, and the radi