By Pulveration are meant all the Benefits of it that accrue to the Pasture of Plants; and by Exhaustion, all the Injuries that can be done to that Pasture, except Burning. And as the Benefits of Pulveration visibly continue for several Years, so do the Injuries of Exhaustion; which appear by the Ends of some of my Rows that have been cleansed of Weeds in their Partitions by the Hand-hoe, and the other Ends of the same Rows not cleansed; the Difference is visible in the Colour of the Wheat in the Third and Fourth following Crops, equally managed; and this is no more to be wondered at, than that Two unequal Sums, being equally increased or diminished, should remain unequal, until an Addition to the lesser, or a Subtraction from the greater, be made; which, in case of the Soil, must be either by a greater Pulveration, or a lesser Exhaustion. ’Tis by this that both Ends of these Rows in time become equal: For tho’ Ten Plants that produce an Ounce of Wheat, insume more _Pabulum_ than one Plant that produces the same Quantity (the Reason for which is given in the Note on _p._ 121.); yet a Plant that produces Six or Seven Drams, insumes less than one that produces an Ounce; for a Plant which produces Six Drams of Wheat cannot be a poor one, and therefore insumes no more _Pabulum_ than in proportion to its Augment and Product. Thus the Soil of those Ends, which, by being doubly exhausted by Weeds and Wheat plants, was made poorer, gradually recovers an Equality with the other Ends, by being for several Years less exhausted than the other Ends are by larger Plants, whilst the Number of Plants, and the Pulveration of each, are equal. To the Reasons already given there is another to be added, why Horse hoed Wheat exhausts the Soil less than sown Crops, where the Product of Wheat produced by each is equal: Which Reason is, that the former has much less Straw than the latter; as appears by the different Quantities of Grain that a Sheaf of each of equal Diameter yields; one of the former yielding generally double to one of the latter; for a Sheaf of the sown has not only more small Under-ears, but also its best Ears bear a less Proportion to their Straw than the other; for a Straw of sown Wheat Six Feet high, I have found to have an Ear but of half the Size of an Ear of drilled Wheat on a Stalk Five Feet high, having measured both of them standing in the Field, and rubbed out the Grain of them. This Difference I impute to the different Supply of Nourishment at the time when the Ears are forming. Thus the sown Crop exhausts a Soil much more by its greater Quantity of Straw. And this is one Reason why annual Crops of sown Wheat cannot succeed as Crops of Horse hoed Wheat do. There must be Dung and Fallow to repair the Exhaustion of the sown; neither of which are necessary for Crops of the Horse-hoed.