Modelling soil-residue-machine interactions using the discrete element method (DEM)

Abstract

A comprehensive understanding of the interactions between soil, crop residue, and tillage implements is critical for advancing the efficiency and sustainability of conservation agriculture. This study integrated laboratory and field experiments with discrete element method (DEM) simulations to investigate soil–residue–machine dynamics across two common tillage practices (disc tillage and subsoiling). A concave disc was used in a controlled soil bin experiment to examine the effects of corn residue length and disc operational angles on soil cutting forces and residue incorporation. Experimental findings showed that longer residue lengths increased both draft force and residue incorporation rate, with the developed DEM model predicting these responses with average relative errors of 9.0% for residue incorporation and 18.2% for draft force. Further, a DEM model simulating soil–cornstalk–disc interactions was established and validated, successfully predicting corn stalk cutting effectiveness and soil cutting forces with an overall relative error of 16.4%. Micro-dynamic analysis revealed that soil bulk density and disc type significantly influenced corn stalk sinkage and soil support forces. In addition to residue cutting studies, the effects of soil heterogeneity defined as vertical spatial variation in soil properties, were explored by developing layered DEM soil models. Simulations of subsoiler performance demonstrated that incorporating heterogeneity improved the prediction accuracy for disturbed soil area, while all models showed acceptable accuracy for predicting soil disturbance width. Finally, the dynamics of wheat residue management with a tandem disc harrow were studied, showing that tillage direction, disc angle, travelling speed, and working depth significantly influenced soil surface roughness, draft force, and soil cutting efficiency. Tillage direction perpendicular to the wheat stubble rows produced lower surface residue cover compared to the tillage direction parallel to the wheat stubble rows. Collectively, these studies contribute to a deeper understanding of soil-residue-machine interactions, offering validated simulation approaches and insights to optimize tillage implement design and operation for enhanced conservation tillage.