A compact, coherent mass of soil varying in size from 0.39–9.75 in (10–250 mm). Clods are produced by operations like plowing, cultivation, and digging, especially on soils that are too wet or too dry. They are usually formed by compression, or by breaking off from a larger unit. Tractor attachments like disks, spike-tooth harrows, and rollers are used to break up clods during seedbed preparation.