text:  A rule for the quantity of farm-yard dung to be applied according to the length of the rotation as given by Dr Coventry is that five tons per acre are required every year to sustain the fertility of soil; and therefore land which is dunged every four years in a rotation of four courses should receive with the fallow-crop twenty tons per acre; in a five-course shift twenty-five tons; in a six-course shift thirty tons and so on