Modelling residue incorporation of selected chisel ploughing tools using the discrete element method (DEM)

Chisel ploughing is a widely used tillage approach for effective residue management in conservative agriculture. Understanding different chisel ploughing tools and their interactions with soil and residue is critical for the design of conservation tillage machines. Four tools, including a narrow sweep, a wide sweep, a reversible shovel, and a twisted shovel were tested in a soil bin with corn residue being included to represent a real field condition. Soil cutting forces, soil and residue displacements, and residue cover were measured. A soil-tool-residue interaction model was developed using the discrete element method to reproduce the soil bin test. The model was validated with the test results. The validated model was then used to investigate the effects of working speed (from 6 to 16 km/h) on the tillage performance of the chisel ploughing tools. The model had an overall relative error of 11.5% as compared with soil bin test results. Increasing the speed increased soil cutting forces, soil and residue displacements, residue cover reduction, and kinetic energy, but decreased the contact numbers between soil and residue of any given tool. Comparing among the tools, the twisted shovel had the highest residue cover reduction of 19.9% at the speed of 16 km/h and the reversible shovel had the least draft force of 130.3 N at the speed of 6 km/h. The simulation results are useful for assessing design alternatives of soil-engaging tools and evaluating residue management practices of chisel ploughing.