When strong Land is plow’d, and not sufficiently, so that the Parts remain gross, ’tis said to be rough, and it has not the Benefit of Tillage; because most of the artificial Pores (or Interstices) are too large; and then it partakes of the Inconveniences of the hollow Land untill’d.
For when the light Land is plow’d but once, that is not sufficient to diminish its natural Hollowness (or Pores;) and, for Want of more Tillage, the Parts into which ’tis divided by that once (or perhaps twice) Plowing, remain too large; and consequently the artificial Pores are large also, and, in that respect, are like the ill-till’d strong Land.
Light-land, having naturally less internal Superficies, seems to require the more Tillage[25] or Dung to enrich it; as when the poor, hollow, thin Downs have their upper Part (which is the best) burnt, whereby all, (except a Caput Mortuum) is carried away; yet the Salts of this spread upon that barren Part of the Staple, which is unburnt, divide it into so very minute Particles, that their Pasture will nourish two or three good Crops of Corn: But then the Plough, even with a considerable Quantity of Dung, is never able afterwards to make a Division equal to what those Salts have done; and therefore such burnt Land remains barren.
[25]As for puffy Land, which naturally swells up, instead of subsiding, tho’ its Hollowness is much abated by Tillage, yet it is thought little better than barren Land, and unprofitable for Corn: But what we usually call Light-land, is only comparatively so, in Respect of that which is heavier and stronger. And this Sort of Light land becomes much lighter by being ill-till’d; the unbroken Pieces of Turf underneath undissolved, forming large Cavities, increase its Hollowness, and consequently its Lightness: I have often known this Sort of Land despis’d by its Owners, who fear’d to give it due Tillage, which they thought would make it so light, that the Wind would blow it away; but whenever such has been thoroughly till’d, it never fail’d to become much stronger than before; and considering that ’tis till’d with less Expence than very strong Land, it is, for several Sorts of Corn, found to be more profitable than Land of greater Strength and Richness, that is more difficult to be till’d.
And I am apt to think, that this Sort of Light-land acquires more Cement, by having its external Superficies often changed, and exposed to the Dews, and other Benefits of the Atmosphere, as well as by the Increase of (its internal Superficies, which is the Surfaces of all the divided Parts of Earth, or) the Pasture of Plants; the one being augmented by the other; i. e., that into the more Parts the Earth is broken, the more Cement will it attain, from the Sulphur, which is brought by the Dews.
Artificial Pores cannot be too small, because Roots may the more easily enter the Soil that has them, quite contrary to natural Pores; for these may be, and generally are, too small, and too hard for the Entrance of all weak Roots, and for the free Entrance of strong Roots.
Insufficient Tillage leaves strong Land with its natural Pores too small, and its artificial ones too large. It leaves Light-land, with its natural and artificial Pores both too large.
Pores that are too small in hard Ground, will not easily permit Roots to enter them.
Pores that are too large in any Sort of Land, can be of little other Use to Roots, but only to give them Passage to other Cavities more proper for them; and if in any Place they lie open to the Air, they are dry’d up, and spoil’d, before they reach them.
For fibrous Roots (which alone maintain the Plant; the other Roots serve for receiving the Chyle from them, and convey it to the Stem) can take in no Nourishment from any Cavity, unless they come into Contact with[26], and press against, all the Superficies of that Cavity, which includes them; for it dispenses the Food to their Lacteals by such Pressure only: But a fibrous Root is not so press’d by the Superficies of a Cavity whose Diameter is greater than that of the Root.