The Horse-hoe will, in wide Intervals, give Wheat, throughout all the Stages of its Life, as much Nourishment as the discreet Hoer pleases.
Secondly, Want of Air.
Air, being a Fluid, moves most freely in a right or strait Line; for there the fewest of its Parts meet with any Resistance; as a strait River runs swifter than a crooked one, from an equal Declivity; because more of the Water strikes against the Banks at the Turnings, and is there somewhat retarded: and the rest moving no faster than in the strait River, the whole Stream of the crooked must be slower in its Course, than that of the strait River.
The Air cannot pass thro’ sown Corn in a direct Line, because it must strike against, and go round every Plant, they standing all in the Way of its Course, which must stop its Current near the Earth.
And the Air amongst sown Corn is like Water amongst Reeds or Osiers in the Side of a River; it is so stopp’d in its Course, that it almost becomes an Eddy; and since Air is about Eight hundred Times lighter than Water, we may suppose its Current thro’ the Corn is more easily retarded, especially near the Earth, where the Corn has occasion for the greatest Quantity of Air to pass: For, tho’ the upper Part of the Wheat be not able to stop a slow Current of Air, yet it does so much raise even a swift one, as to throw it off from the Ground, and hinder it from reaching the lower Parts of the Stalks, where the Air must therefore remain, in a manner, stagnant; and the thicker the Wheat is, where it stands promiscuously, the less Change of Air can it have, tho’ the greater the Number of the Stalks is, the more fresh Air they must require.
But the confused Manner in which the Plants of sown Wheat stand, is such, that they must all oppose the free Entrance of Air amongst them, from whatever Point of the Compass it comes.
Now it is quite otherwise with Wheat drill’d regularly with wide Intervals; for therein the Current of Air may pass freely (like Water in a strait River, where there is no Resistance), and communicate its Nitre to the lower as well as upper Leaves, and carry off the Recrements they emit, not suffering the Plants to be weakened, as an Animal is, when his Lungs are forc’d to take back their own Expirations, if debarr’d from a sufficient Supply of fresh untainted Air. And this Benefit of fresh Air is plentifully, and pretty equally, distributed to every Row in a Field of ho’d Wheat.
Thirdly, Want of the Sun’s Rays.
Sown Wheat-plants, by their irregular Position, may be said to stand in one another’s Light, for want of which they are apt to fall.
’Tis true the whole Field of Plants receive the same Quantity of Sun-beams amongst them, whether they stand confusedly, or in Order: But there is a vast Difference in the Distribution of them; for none or the very least Share of Beams is obtain’d by those Parts which need the greatest Share, in the confused Plants. And when the crural Parts, that should support the whole Body of every Plant, are depriv’d of their due Share of what is so necessary to strengthen them, the Plants (like Animals in the same Case) are unable to stand.