FRACTURING OF SOIL CLODS AND THE SOIL CRUMBLING EFFECTIVENESS OF DRAFT TILLAGE IMPLEMENTS

An effectiveness criterion relating the mechanical work done by an implement on a soil and the aggregate size reduction obtained, is formulated. It relies on a drop test of soil clods giving a linear relation between the drop energy and the new aggregate surface created when the clod fractures. The aggregate size reduction effectiveness of six draught tillage implements is investigated and one version is found to be the best. The aggregate size distribution after tillage work was mainly independent of the implement used, and largely determined by the soil state and the soil's ability to store strain-energy before fracture.