Weed seed burial as affected by mouldboard design parameters, ploughing depth and speed: DEM simulations and experimental validation

Abstract

Discrete element method (DEM) was employed to model and optimise the weed seed burial and tillage forces as affected by mouldboard design parameters (i.e. the cutting angle (ε), the setting of the share angle (θs), the curvature parameter (q)), ploughing depth and speed. Several mouldboards were designed with combinations of ε at 40°, 45°, 50° and 60°, θs at 25°, 35°, 45° and 55° and q at 20, 22, 24 and 30. A total of 64 DEM simulations were performed and the resulting percentage of weed seed burial and tillage forces were analysed. Optimisation of mouldboard design parameters was performed using the response surface methodology (RSM). The optimal combination resulted in ε = 32.3°, θs = 47.8°, and q = 28.2. Then, the combined influence of ploughing depth and speed was investigated and the values of 0.3 m and 1 ms−1 were selected as the best combination to achieve maximum weed seed burial. For validation of the simulation results, a full scale mouldboard plough was tested in the field with blue-coloured polyethylene pellets as a layer of weed seed on the topsoil. Comparison of the measured and predicted weed seed burial below the critical burial depth (i.e. 0.15 m) showed the simulated percentage of weed seed burial within bounds of ±15% of the measured values with R2 of 0.93. As a conclusion, DEM can be a useful tool to optimise the design of tillage tools to improve the effectiveness of tillage.