To address the insufficient passability of existing micro-ridge direct seeders for rapeseed in rice stubble fields, which is primarily caused by high residue coverage, heavy clay soils, mutual interference among soil-slice transfer trajectories, and the structural configuration and spatial arrangement of soil-engaging components, a short-distance furrow-turning residue-burial scheme was proposed in this study. Based on the agronomic requirements of residue incorporation and micro-ridge seedbed preparation in rice stubble fields, a furrow-turning residue-burial device consisting of four moldboards plough with short-distance furrow slice turning characteristics was designed and integrated into the micro-ridge direct seeder. The proposed device was developed to improve residue-burial performance and machine passability under high-residue field conditions. A comparative analysis of furrow slice motion characteristics under different furrow-turning modes was conducted to investigate the effects of soil-transfer patterns on residue burial and passability. The results revealed that the passability of the moldboard group could be effectively improved when furrow slices underwent rolling turnover accompanied by short-distance lateral displacement. In addition, increasing the furrow slice turning rate was found to be beneficial for enhancing residue-burial performance and improving the incorporation of crop residues into the soil profile. These results indicated that the furrow slice turning characteristics had important effects on both residue incorporation and operating performance. To investigate the mechanism governing furrow slice movement during the furrow slice turning process, a mathematical model of the moldboard guide curve and the variation law of the generatrix angle were established. Based on these models, the moldboard plough surface equation was developed. Furthermore, through motion analysis of the furrow slice on the moldboard plough surface, a three-dimensional kinematic model describing furrow slice displacement in the longitudinal, lateral, and vertical directions was constructed. The establishment of these models provided a theoretical basis for analyzing furrow slice movement characteristics and evaluating the effects of moldboard plough structural parameters on furrow slice transfer behavior. Theoretical analysis demonstrated that the ratio of moldboard breast height to wing height, lead coefficient, and working width were the key structural parameters influencing the lateral displacement distance of furrow slices as well as the residue-burial performance of the moldboard. According to the furrow slice movement characteristics and the geometric constraints of the moldboard plough structure, the theoretical ranges of these parameters were subsequently determined, providing the basis for structural parameter optimization. To optimize the structural parameters of the moldboard plough, a Box–Behnken experimental design was implemented using the discrete element method (DEM) in EDEM software. Residue burial rate and lateral furrow slice displacement distance were selected as the evaluation indices. The simulation results indicated that the optimal parameter combination consisted of a ratio of moldboard breast height to wing height of 2, a lead coefficient of 6.8×10⁻³, and a working width of 170 mm. Under these optimized conditions, the residue burial rate reached 74.1%, while the lateral displacement distance of the furrow slice was reduced to 451 mm. These results indicated that the proposed moldboard plough structure could simultaneously achieve effective residue incorporation and short-distance furrow slice transfer. Field experiments were subsequently conducted to verify the performance of the residue-burial device under different crop-stubble conditions. The results showed that the furrow slice turning rates of the device under wheat stubble, rapeseed stubble, and rice stubble conditions were 82.31%, 84.45%, and 85.77%, respectively. No blockage or clogging occurred during operation, demonstrating excellent passability and stable working performance under different field conditions. Furthermore, performance tests of the complete machine were carried out to evaluate its ability to satisfy the agronomic requirements of micro-ridge direct seeding. The results showed that, after operation of the complete machine, the residue burial rate reached 82.35%, the soil pulverization rate reached 81.69%, the average micro-ridge height was 147 mm, and the average micro-ridge spacing was 350 mm. The stability coefficients of micro-ridge height and micro-ridge spacing were 80.33% and 93.23%, respectively, indicating that the machine could effectively satisfy the agronomic requirements for micro-ridge direct seeding of rapeseed in rice stubble fields. The results of this study provide theoretical support and technical references for the design and optimization of furrow slice turning residue-burial devices with improved passability and offer a feasible approach for enhancing residue management and seedbed preparation quality in micro-ridge direct seeding systems for rapeseed cultivation in rice stubble fields.

The compatibility between the morphological characteristics (MCs) of rapeseed bare-root seedlings and transplanters directly affects planting quality. To improve the adaptability of transplanters to the MCs of different rapeseed cultivars, this study focused on six winter rapeseed cultivars (A1: Huyou 17, A2: Huayouza 9, A3: Fengyou 520, A4: Zhongyou 108, A5: Zheyou 50, and A6: Huayouza 62). Five MCs—root length (RL), seedling height (SH), root diameter (RD), stem thickness (ST), and seedling width (SW)—were measured during the seedling ages (25-40 d). Multiple comparisons were conducted to identify cultivars with no significant differences (NSD, α=0.05) in MCs, while skewness and kurtosis were analyzed to assess temporal variations in MC distributions. Quadratic polynomial regression was employed to model the growth trends of MCs for each cultivar. The results showed that the skewness and kurtosis ranges of MCs were –0.65 to 1.16 and 1.62 to 6.28, respectively, indicating significant variability in growth symmetry and concentration both within and among cultivars. As seedling age increased, the number of cultivars with NSD in MCs progressively decreased (25 d: 5; 30 d: 4; 35 d: 3; 40 d: 2), but A3, A5, and A6 maintained consistent stability before 35 d. Based on MC statistical analysis, the key design parameters for the transplanter were determined as follows: flat belt width was 180 mm, positioning bar spacing was 70 mm, flexible belt width was 150 mm, clamping distance was 8 mm, seedling drop height was 180 mm, and planting depth was 40 mm. Field tests demonstrated that the transplanter exhibited superior compatibility with cultivars A3, A5, and A6, achieving seedling delivery success rates of 93.75% (A3), 93.23% (A5), and 92.71% (A6), along with significantly higher planting success rates compared to the control group (A1, A2, A4). This study provides a theoretical basis for optimizing the compatibility between transplanters and rapeseed bare-root seedlings, as well as guiding the structural design of transplanting machinery.