To solve the problems of high resistance and blockage in stubble-breaking operations, it is necessary to reveal the interaction mechanism between disc coulters and crop root–soil composites. This study developed a discrete element method–multi-body dynamics (DEM-MBD) coupling model of the stubble-breaking operation and verified the accuracy of the model through soil bin tests (error < 20%) and field experiments (error < 32%). The model was used to investigate the effects of different design parameters (coulter type and disc radius) and operating parameters (tillage speed and depth) on the stubble-breaking operation. The results showed that due to the significant strengthening effect of roots on soil, the resistance of disc coulter stubble-breaking operation was high; the number of roots in contact with the blade edge and the amount of root deformation significantly affected the resistance of the disc coulter; irreversible deformation of roots and soil could easily lead to the holes and root hairpin effects in the seeding furrow; compared to plain disc coulters, the difference in the time of deformation and fracture of the roots made the resistance of the notched coulter lower. The wavy disc coulter with a longer edge curve made its resistance higher; the disc coulter with a greater radius, higher tillage speed, and deeper tillage depth significantly increased the tillage resistance. However, the disc coulter with a greater radius or a higher tillage speed was beneficial for improving stubble-breaking performance. This study revealed the interaction mechanism between disc coulters and maize root-soil composites, providing a theoretical basis for the optimization design of no-till stubble-breaking devices.

Rural domestic waste slag is often used to prepare organic fertilizer, thereby improving the environment and saving resources. The mixing of the raw materials and fermentation bacteria is key to the preparation of organic fertilizers. In the organic fertilizer continuous conveying device designed in this study, a paddle was substituted for a screw blade for transporting the material to improve the mixing performance. A discrete element method (DEM) model was established for the device. The influences of the paddle rotational speed n and paddle angle α were studied. The simulation results showed that mixing performance was improved when the paddle angle α was 45° and the paddle rotational speed n was 75 rpm, with an RSD of 15.96%. The larger the paddle rotational speed n, the larger the average normal contact force, and the smaller the influence of the paddle angle α. In addition, the paddle rotational speed n and paddle angle α could affect the speed of the particles in all directions in the device. The trajectory of a single particle in the device was analyzed, and it was found that changing the paddle parameters could improve the path length and improve the mixing performance. The research results lay the foundation for designing reasonable paddle parameters.