Characterization of Physical, Mechanical, and Shear Properties of Cabbage Stubble and Calibration of Its Discrete Element Method Parameters

Cabbage is a major leafy vegetable in China, but its post-harvest stubble—characterized by high lignification, a thick primary taproot, well-developed lateral roots, and strong root–soil anchorage—poses significant challenges for mechanical incorporation. To address this, a discrete element method (DEM) model of ‘Zhonggan 21’ cabbage stubble was developed. A geometric model was established using root depth as the primary characteristic dimension. Intrinsic physical properties and contact mechanical parameters were systematically measured. DEM parameters were calibrated against shear test results, yielding the following optimal parameter set: tangential stiffness per unit area of 5.54 × 109 N·m−3, a tangential bond strength of 1.06 × 106 Pa, and a bonding radius coefficient of 1.07. Under this configuration, the simulated peak shear force deviated from the experimental measurement by merely 1.77%. This work delivers a full-scale property profile of cabbage stubble and constructs a validated DEM model, providing a robust foundation for designing stubble incorporation machinery and advancing low-draft, energy-saving tillage equipment to support sustainable vegetable cropping systems.