[26]Roots cannot have any Nourishment from Cavities of the Earth that are too large to press against them, except what Water, when ’tis in great Quantity, brings to them, which is imbibed by the gentle Pressure of the Water; but when the Water is gone, those large Cavities being empty, the Pressure ceases; and this is the Reason, that when Land has few other but such large Cavities, the Plants in it always suffer more by dry Weather, than in Land which by Dung or Tillage has more minute and fewer large Cavities.
There may be some Moisture on the Superficies of large Cavities; but without Pressure the fibrous Roots cannot reach it; and very little or no Pressure can be made to one Part of the Root’s Superficies, unless the Whole that is included be pressed.
If it be objected that a Charlock-Plant, when pulled up, and thrown upon the Ground, will grow thereon; this proves nothing against the Necessity of Pressure, &c. for the Weight of that Plant presses some of its Roots so closely against the Ground, that they send out (unless the Weather be very dry) new Fibres into the Earth; and there they are pressed in all their Superficies; without which Fibres the Plant doth not grow.
The Surfaces of great Clods form Declivities on every Side of them, and large Cavities, which are as Sinks to convey, what Rain and Dew bring, too quickly downwards to below the plow’d Part.
The first and second Plowings with common Ploughs scarce deserve the Name of Tillage; they rather serve to prepare the Land for Tillage.
The third, fourth, and every subsequent Plowing, may be of more Benefit, and less Expence, than any of the preceding ones.
But the last Plowings will be more advantageously perform’d by Way of Hoeing, as in the following Chapters will appear.
For the finer Land is made by Tillage, the richer will it become, and the more Plants it will maintain.
It has been often observ’d, that when Part of a Ground has been better till’d than the rest, and the whole Ground constantly manag’d alike afterwards for six or seven Years successively; this Part that was but once better till’d, always produc’d a better Crop than the rest, and the Difference remain’d very visible every Harvest.
One Part being once made finer, the Dews did more enrich it; for they penetrate within and beyond the Superficies, whereto the Roots are able to enter: The fine Parts of the Earth are impregnate, throughout their whole Substance, with some of the Riches carried in by the Dews, and there reposited; until, by new Tillage, the Insides of those fine Parts become Superficies; and as the Corn drains them, they are again supply’d as before; but the rough large Parts cannot have that Benefit; the Dews not penetrating to their Centres, they remain poorer.