Evaluation of rotary mixing effects on soil structure and tillage resistance using discrete element method

Application of the Discrete Element Method to Soil–Tool Interaction: A Critical Narrative Review of Contact Models, Calibration and Predictive Reliability

Numerical modelling of the interaction between soil-engaging tools and agricultural soils has become central to the design of tillage and seeding equipment, where draught reduction, controlled soil disturbance and residue management influence energy use and crop establishment. The discrete element method (DEM), which represents soil as an assembly of interacting particles rather than a continuum, has emerged as the dominant particle-scale approach for this problem. This review critically examines how DEM has been applied to soil–tool interaction, with attention to the choice of contact model, the calibration of microscopic parameters, the treatment of particle size and shape, and the reliability of predictions for draught force, vertical force, soil disturbance and soil translocation. The available evidence indicates that DEM can reproduce measured tillage forces and furrow profiles with useful accuracy across a range of tools, including sweeps, subsoilers, narrow openers, discs and mouldboard ploughs, provided that an appropriate plastic or cohesive-adhesive contact model is combined with carefully calibrated parameters. However, the field is characterised by persistent tensions: between computational tractability and physical fidelity in the selection of enlarged particles; between the many-to-one mapping of calibrated parameter sets and the physical properties they represent; and between force prediction, which is often robust, and soil-movement prediction, which remains more sensitive to particle scaling. Cohesive and adhesive wet soils, high-speed operations, heterogeneous layered profiles and tool wear are comparatively under-represented and less consistently validated. Coupling of DEM with multibody dynamics, computational fluid dynamics and finite element analysis extends its reach but introduces additional calibration and verification burdens. Machine-learning-assisted calibration and improved measurement of soil micro-properties are promising but not yet standardised. The review concludes that confidence in DEM is strongest for relative comparisons of tool geometry in well-characterised cohesionless and lightly cohesive soils, and weaker for absolute prediction in wet, adhesive or rapidly changing field conditions. Priorities include transparent and reproducible calibration, standardised validation metrics, and systematic evaluation across soil types and operating speeds.

DEM-based calibration of paddy soil contact parameters for improved soil-tool interactions

Discrete element model (DEM) parameters are crucial for accurately predicting soil properties and disturbance levels. This study aimed to provide an efficient method for accurately determining DEM parameters for paddy soil. The Hertz-Mindlin and JKR contact models were used to simulate the paddy soil, and the Plackett-Burman, the Steepest Ascent, and the Box-Behnken tests were used to determine the DEM parameters. The accuracy of the established discrete element model was evaluated using actual slump test. The Plackett-Burman test results showed that the soil surface energy, soil-soil rolling friction coefficient, and soil-steel static friction coefficient had a significant impact on the total relative error between the simulation results and the test results. Box-Behnken test optimization results show that the soil surface energy, soil-soil rolling friction coefficient, and soil-steel static friction coefficient are 0.869 J.m², 0.109, and 0.651, respectively. Comparison with actual soil slump test results shows that the calibrated DEM model has an overall relative error of 5.59% and a coefficient of variation of 3.49%. This research can provide a theoretical basis and technical support for subsequent research on soil-machine interaction mechanisms.

Design and testing of a soil-dividing device for a pineapple strip-tillage furrower

To address issues such as high soil backfilling rates and difficulty in maintaining the trench shape during the operation of pineapple strip-rotary cultivators, we designed a V-shaped soil-dividing device. Structural modelling was performed using SolidWorks 2022 by establishing force analysis equations for the soil-dividing device and soil motion trajectory equations. A dynamic simulation model based on the discrete element method was constructed using the EDEM software to determine the structural parameters of the soil-dividing device. Stress analysis conducted using the ANSYS software verified that the structural strength of the soil-dividing device met the application requirements. To optimize operational parameters further, a four-factor, five-level orthogonal rotational combination field trial was designed using the central composite response surface method in Design-Expert 12. The installation distance, V-angle, blade roller speed, and forward speed were defined as the experimental factors, with the soil backfilling rate as the evaluation indicator. We analyzed the effects of various factor interactions on the soil backfilling rate. The experimental results indicated that the minimum soil backfilling rate of 38.12%, which is satisfactory for pineapple planting trenching requirements, was achieved at a V-angle of 30°, forward speed of 3.7 km/h, blade roller speed of 290 r/min, and installation distance of 125 mm. This study has significant implications for advancing the mechanization of pineapple cultivation.

Measurements and DEM modelling of soil shear behavior under varying normal stresses for different soils

Experimental investigation of the spatial movement law of straw–root–soil complexes during slope contour rotational tillage operations based on the tracer method

During contour rotary tillage on sloping terrain, the migration characteristics of the straw–root–soil complex directly affects the effectiveness of straw return and soil sustainability, but the underlying mechanisms remain unclear, hindering the development of specialized rotary tillage equipment. This study uses a self-developed bench test platform for rotary tillage on sloped terrain in hilly and mountainous regions and tracer method to systematically investigate the effects of slope gradient (5°, 10°, 15°), blade shaft rotational speed (200–300 r/min), forward farming speed (0.2–1.0 km/h), and straw content (0.4–1.2 kg/m²) on the migration characteristics of soil aggregates. The test results demonstrate that the forward farming speed is the most effective controllable parameter for suppressing the horizontal and lateral displacement of soil complexes. Increasing the speed from 0.2 km/h to 1.0 km/h can reduce the lateral displacement of straw by 65.3%. An increase in the rotational speed of the blade shaft intensifies the migration of the complex mass, with a notably increased displacement toward the downhill side under steep slope conditions (15°). The slope gradient is the dominant natural factor driving the asymmetric movement of the complex along the lower side of the slope. When the slope increases from 5° to 15°, the lateral displacement of the straw increases by 166%. Straw mulching effectively mitigates tillage-induced soil erosion. When the straw content increases from 0.4 kg/m² to 1.2 kg/m², the lateral soil displacement is reduced by 37.7% to 51.9%. Through orthogonal experiments and response surface analysis, the hierarchical order of the factors influencing soil complex transport was determined. In terms of soil lateral displacement, the primary influencing factor is the slope gradient. With respect to soil horizontal displacement, the dominant factor is the forward farming speed. Corresponding regression prediction models were developed. This study provides the first systematic evaluation of the transport mechanisms governing the straw–root–soil complex on sloped terrain under contour rotary tillage conditions, thereby establishing a theoretical foundation for designing specialized tillage equipment for hillside agriculture and performing quality control in the incorporation of crop residue.

Plot‑Scale Assessment of Sewage Sludge and Biochar Effects on Soil Properties, Soil Erodibility, and Runoff in Contrasting Textural Soil