All sorts of dung and compost contain some matter which, when mixed with the soil, ferments therein; and by such ferment dissolves, crumbles, and divides the earth very much. This is the chief and almost only use of dung.... This proves, that its (manure) use is not to nourish, but to dissolve, i.e., divide the terrestrial matter, which affords nourishment to the Mouths of vegetable roots.
His underestimate of the value of manure.

Horse-Hoeing Husbandry... The fourth edition... corrected. To which is prefixed, a new preface by the editors, etc (ed. 1822)