DEM modelling of crop residue and soil dynamics as affected by the tillage direction of a disc harrow

A comprehensive understanding of crop residue and soil dynamics under tillage is essential for improving the operational efficiency of tillage implements. In this study, a tandem disc harrow and its interaction with wheat-residue in a sandy loam soil were modelled using the discrete element method. The model was able to simulate two tillage directions: perpendicular and parallel to standing wheat-stubble rows (Perp-Direction and Para-Direction). The model was validated using field measured data. Field experiments showed that Perp-Direction produced significantly lower residue cover than Para-Direction (P < 0.05). Both tillage directions resulted in similar stubble forward displacements (mean: 354 mm). The DEM model predicted these variables with an overall relative error of 19.7 %. Simulations further revealed that stubble trajectories and soil cutting forces varied among individual discs due to the tandem configuration of the harrow. These variables were also influenced by operational parameters: disc angle, harrow travelling speed, and working depth. Reducing these operational parameters decreased soil surface roughness in both tillage directions. Conversely, increasing these operational parameters required higher total draft forces and disturbed a larger soil area. However, the soil cutting efficiency, a performance index combining both total draft force and soil disturbance area, declined from 95.9 to 37.3 m 3 MJ −1 under these conditions. Overall, these findings provide useful guidance for optimising tillage direction and operational parameters of tandem disc harrows to enhance field performance. • A DEM model of a tandem disc harrow was developed and validated with field data. • The model simulated soil and wheat stubble under two tillage directions (TD). • TD affected residue cover but minimally influenced stubble displacement. • Larger disc angle, working speed and depth reduced soil cutting efficiency.