Lateritic soils in tropical regions feature cohesive textures and high specific resistance, driving up energy demands for tillage and harvesting machinery. However, current equipment designs lack discrete element models that account for soil moisture variations, and the microscopic effects of water content on lateritic soil deformation remain poorly understood. This study aims to calibrate and validate discrete element method (DEM) models of lateritic soil at varying moisture contents of 20.51%, 22.39%, 24.53%, 26.28%, and 28.04% by integrating the Hertz–Mindlin contact mechanics with bonding and JKR cohesion models. Key parameters in the simulations were calibrated through systematic experimentation. Using Plackett–Burman design, critical factors significantly affecting axial compressive force—including surface energy, normal bond stiffness, and tangential bond stiffness—were identified. Subsequently, Box–Behnken response surface methodology was employed to optimize these parameters by minimizing deviations between simulated and experimental maximum axial compressive forces under each moisture condition. The calibrated models demonstrated high fidelity, with average relative errors of 4.53%, 3.36%, 3.05%, 3.32%, and 7.60% for uniaxial compression simulations across the five moisture levels. Stress–strain analysis under axial loading revealed that at a given surface displacement, both fracture dimensions and stress transfer rates decreased progressively with increasing moisture content. These findings elucidate the moisture-dependent micromechanical behavior of lateritic soil and provide critical data support for DEM-based design optimization of soil-engaging agricultural implements in tropical environments.

Taro (Colocasia esculenta) stems are promising bio-based feedstocks for composite materials, textile fibres and adsorbents; however, a quantitative understanding of how their microstructure governs mechanical behaviour remains lacking, constraining their application. This study conducted mechanical tests and scanning electron microscopy (SEM) tests on stems harvested from different ground elevations. The results show that axial tensile strength (σ_t) and nominal radial compressive stress (σ_c) increase first and then decrease with height above ground. σ_t (2.67 MPa) and σ_c (7.64 MPa) both peak at 50–100 mm above ground level. Furthermore, the ultimate nominal compressive strength (σ_c) is significantly higher than the ultimate tensile strength (σ_t) at all heights above ground. Correlation analysis revealed that cross-sectional area A_c (r = 0.83), fibre bundle area fraction P_c (r = 0.78) and fibre wall thickness T_c (r = 0.77) were significantly positively correlated with σ_t, while A_c (r = 0.62) and T_c (r = 0.70) were positively correlated with σ_c. The tensile and compressive properties are closely associated with three microstructural parameters: cross-sectional area, fibre bundle area fraction, and fibre wall thickness—whereas fibre cell area shows only weak correlations with all mechanical indicators (r < 0.5) and is not a key regulatory factor. The stem cross-section transitions from crescent at the base to near-circular at the apex, with the reduction in bearing area underlying the decline in mechanical properties. These results offer a fundamental basis for tailoring mechanical preprocessing parameters and for selective utilisation of stem segments with distinct mechanical performance, thereby supporting the efficient conversion of this abundant biomass into value added materials.