Clod movement and tillage tool characteristics for modelling tillage erosion

Soil erosion due to tillage is proportional to the local slope curvature. The value of the coefficient of proportionality (tillage transport coefficient) depends on the interaction between tillage tool and soil. These interactions have been partly modelled as a 3 phase motion: drag (depending only on tool characteristics) when the soil is in contact with the instrument; jump (not necessarily present for all tools) when the soil loses contact with the tool and is ejected; rolling when the clods roll and jump in relatively close contact with the soil surface. Three sets of equations have been proposed and assembled into a computer program (SETI, from ‘Soil Erosion by Tillage’). The model simulates the 3D behaviour of the transported soil. The SETI performances are exemplified through the case of the mouldboard plough. The graphs show the effect of slope gradient and of tillage direction. The simulated trends closely resemble those observed in other studies. The major improvement with respect to previous models is that tool characteristics are explicitly taken into account.