Discrete element modelling of the effect of disc angle and tilt angle on residue incorporation resulting from a concave disc

Abstract

Understanding crop residue behaviour during tillage is critical for improving performance of tillage tools for conservation agriculture. A laboratory experiment was conducted using a concave disc to incorporate corn residue into sandy loam soil. Dynamic attributes, including soil cutting forces and residue incorporation, were measured under different lengths (75, 125, and 200 mm) of corn residue at constant disc and tilt angles. A residue-disc-soil interaction model was developed using discrete element method (DEM). Model parameters were calibrated and validated using experimental data. The validated model was used to predict the dynamic attributes at different disc and tilt angles. Experimental results demonstrated a general increasing trend in draft force (FD) and residue incorporation rate (RI), as the corn residue length increased. The two calibrated model parameters, stiffness of soil particle and stiffness of soil-residue interface were 1.15 × 106 and 13.5 N/m respectively. The validated model had an average relative error of 9.0 % and 18.2 % for predicting RI and FD respectively, as compared with the measurements. Within the angle range of 10° to 30°, the FD and RI decreased as the tilt angle (α) increased, whereas increased as the disc angle (β) increased. The effects of β were more pronounced than those of α. The optimal angles were α = 20°, β = 25° which resulted in a minimum FD and a maximum RI. The results provided new insight into residue-disc-soil dynamics and could be used to guide the selection of disc operating parameters.