Both cannot be true.
If the latter were true, Change of Sorts would be as necessary as it is commonly thought. But if the former be true, as I hope to prove it is, then there can be no Use of changing of Sorts in Respect of different Nourishment.
If in this Series of Crops each Sort were so just as to take only such Particles, as are peculiarly proper to it, letting all the rest alone to the other Sorts to which they belonged, as the Doctor imagines; then it would be equal to them all, which of the Sorts were sown first or last: But let the Wheat be sown after the Barley, Pease, and Oats, instead of being sown before them, and then it would evidently appear, by that starv’d Crop of Wheat, either that some or all of those other Grains had violated this natural Probity, or else that Nature has given to Vegetables no such Law of Meum and Tuum[207].
[207]A Charlock could not rob a Turnep, and starve it, more than several Turneps can do, unless the Charlock did take from it the same Particles which would nourish a Turnep; and unless the Charlock did devour a greater Quantity of that Nourishment than several Turneps could take.
Flax, Oats, and Poppy, could not burn or waste the Soil, and make it less able to produce succeeding Crops of different Species, unless they did exhaust the same Particles which would have nourish’d Plants of different Species: For let the Quantity of Particles these Burners take be never so great, the following Crops would not miss them, or suffer any Damage by the Want or Loss of them, were they not the same Particles which would have nourished those Crops, if the Burners had left them behind, quiet and undisturbed. Neither could Weeds be of any Prejudice to Corn, if they did draw off those Particles only that suit the Bodies of Weeds, the rest lying all quiet and undisturbed the while. But constant Experience shews, that all Sorts of Weeds, more or less, diminish the Crop of Corn.
If these Things were, as the Doctor affirms, why do Farmers lose a Year’s Rent, and be at the Charge of fallowing and manuring their Land, after so few Crops; since there are many more Sorts of Grain as different from these and one another, as those are which they usually sow?
They still find, that the first Crops are best; and the longer they continue sowing, the worst the last Crops will prove, be they of never so different a Species; unless the Land were not in so good Tilth for the first Crop as for the subsequent; or unless the last sown be of a more robust Species.
This Matter might be easily clear’d, could we perfectly know the Nature of those supposed unsuitable[208] Particles; but, in Truth, there is no more to be known of such of them, than that they are carried away by the Atmosphere to a Distance, according to the Velocity of the Air; perhaps several Miles off, at least, never like to return to the Spot of Ground from whence the Plants have raised them.
[208]But we must not conclude, that these Particles, which pass through a Plant (being a vastly greater Quantity than those that abide in it for its Augment), are all unsuitable, because no one of them happens to hit upon a fit Nidus: For since the Life of Animals depends upon that of Plants, ’tis not unreasonable to imagine, that Nature may have provided a considerable Overplus for maintaining the Life of individual Plants, when she has provided such an innumerable Overplus for continuing every Species of Animals.
But suppose these cast-off Particles were, when taken in, unfit for the Nourishment of any manner of Vegetables: Then the Doctor must fansy the Wheat to be of a very scrupulous Conscience, to feed on these Particles, which were neither fit for its own Nourishment, nor of any other Plant; and at the same time to forbear to take the Food of Barley, Pease, and Oats, letting that lie still and undisturb’d the while, as he says it does, tho’ he gives no manner of Reason for it.