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.

Rapeseed is one of the most significant oil crops globally, and mechanization is critical for its efficient harvesting. Swath harvesting, a method that involves cutting the crop and leaving it in windrows to dry before threshing, is widely favored for mitigating the issues of inconsistent maturity and high pod shattering losses associated with direct combining. However, existing rapeseed swathing equipment faces significant technical bottlenecks that hinder operational efficiency and agronomic quality. Specifically, conventional headers utilizing side delivery modes often suffer from poor uniformity, resulting in disordered windrows and stalk entanglement. Conversely, headers designed for center delivery frequently produce dense, rope-like windrows that are ill-suited for the rapid drying of high-yield, high-biomass plant varieties, leading to potential mildew and grain quality degradation due to poor internal ventilation. Furthermore, the prevailing market solution relies on dedicated headers for either side or center delivery, forcing farmers to invest in multiple specific attachments, thereby increasing machinery costs and reducing field adaptability. To address these distinct practical challenges and improve the adaptability of harvesting machinery, this study proposes and develops a novel, adjustable delivery header based on a modular design concept. The core innovation of this system lies in its ability to integrate both side delivery and center delivery functions within a single unit. This integration is achieved through a transformable conveying module that allows for the precise adjustment of the spatial position of the delivery mechanism. Consequently, the header can realize on-demand switching between the two delivery modes, enabling operators to adapt to varying field conditions and crop densities without replacing the entire header assembly. To ensure the scientific rigor of the design, a comprehensive kinematic analysis was conducted. This study investigated the complex motion of rapeseed plants during the cutting, conveying, and laying stages under both operational modes. By analyzing the velocity vectors and trajectory equations of the stalks, the research revealed the intrinsic mapping mechanism between key operating parameters and the final windrow morphology. Additionally, the theoretical model was refined by incorporating strict boundary constraints derived from the agronomic requirements of rapeseed swath harvesting, such as minimizing impact force to reduce seed loss and ensuring optimal stubble height for windrow support. Validating the theoretical framework involved a rigorous experimental approach. A quadratic regression orthogonal rotation combination experiment was designed to quantify the interaction effects of critical variables. Through multi-objective optimization analysis, the study sought to balance competing goals such as maximizing uniformity while minimizing structural complexity. The optimization process yielded a precise combination of operational parameters: a reel speed of 32 r/min, a conveyor belt linear speed of 2 m/s, a forward speed of 0.8 m/s, and a conveyor belt inclination angle of 29°. Field verification trials were subsequently conducted to evaluate the performance of the prototype under real-world agricultural conditions. The quantitative results demonstrated superior performance metrics. The average laying angle of the stalks was recorded at 14.5°, a critical parameter that facilitates optimal airflow through the windrow. The consistency of the operation was highlighted by the minimal difference of only 3.7° between the average angles of the upper and lower stalk layers, indicating a highly uniform structure. Furthermore, the average laying width and thickness were measured at 1128.4 and 634.2 mm, respectively. Most notably, the coefficients of variation for laying width and thickness were suppressed to 7.6% and 11.6%, respectively, values that are significantly lower than industry standards, thereby proving the operational stability of the system. In conclusion, this research effectively resolves the longstanding issues of poor adaptability and the need for specialized equipment in rapeseed harvesting. By realizing the orderly guidance of stalks and the formation of flattened, well-ventilated windrows, the developed header significantly improves laying consistency and drying efficiency. These advancements not only reduce the risk of post-harvest losses but also provide a substantial technical reference for the future optimization and structural design of intelligent rapeseed swath harvesting equipment.

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.

Microgreen cultivation is often required for the precise sowing due to the small size and sensitivity of the seeds. However, it is still lacking in the equipment for the multi-row parallel mechanized seeding. Manual sowing is also confined to the uniform distribution during operations, due to the high risk of seed damage. In this study, a pneumatic needle suction device was developed for precision seed metering. A kinetic model was established to analyze the seed adsorption via the suction needles in the seeding device. Computational Fluid Dynamics simulations were conducted to optimize the airflow patterns and pressure distribution around the needles, in order to realize the efficient seed pickup and release. The key mechanical components were determined with their operational parameters, including a vibratory seed-feeding device, a pivoting air cylinder for needle movement, a seed tray conveyance, and a tray stacking mechanism. A systematic experiment was employed to identify the optimal combination of the operational parameters. The critical factors were determined, such as the vacuum pressure level, the orifice diameter of the suction needles, and the vibration frequency of the pneumatic vibrator in the feeding system. Firstly, single-factor experiments were performed to determine the approximate effective ranges for each factor. Two representative microgreen seeds were selected: the Toona sinensis and Medicago sativa. The results indicated that for Toona sinensis seeds, the superior seeding performance was achieved within the following ranges: the suction orifice diameters between 0.6 and 1.2 mm, vibration frequencies from 10.5 to 11.5 Hz, and vacuum pressures ranging from 6 to 11 kPa. In the smaller Alfalfa seeds, the effective parameters were a slightly broader orifice diameter range of 0.5 to 0.7 mm, but a narrower vibration frequency band of 9 to 10.5 Hz and a lower vacuum pressure requirement of 5 to 9 kPa. Subsequently, a quadratic orthogonal rotation combination was implemented to determine the optimal parameter and factor interactions. This advanced statistical analysis revealed that the optimal seeding performance for the Toona sinensis was obtained at a vibration frequency of 12 Hz, a suction needle orifice diameter of 0.9 mm, and a vacuum pressure of 7.5 kPa. In the Alfalfa seeds, the optimal combination of the parameters was a vibration frequency of 10 Hz, an orifice diameter of 0.6 mm, and a vacuum pressure of 5 kPa. Bench tests were finally conducted to validate the performance under these optimal parameters. The results demonstrated that there was a highly qualified seed index of 95.48% and a very low miss-seeding index of merely 1.70% for the Toona sinensis. In Alfalfa, the excellent performance was also obtained with a qualified index of 92.10% and a miss-seeding index of 2.30%. The pneumatic seeding device fully met the agronomic requirements for the precision sowing of the microgreen seeds. In conclusion, a pneumatic seed metering device was successfully optimized for the microgreen seed sowing. The theoretical modeling, CFD simulation, and experiment were combined to determine the optimal parameters for the different seed types. The crucial guidance was provided for the operational adjustment of such equipment. The findings can offer valuable insights and a solid reference for future structural optimization of the high-performance seeding devices in the emerging microgreen industry. A technological gap can be effectively bridged for the high efficiency of microgreen production in small-scale precision agriculture.

This study aimed to establish, calibrate and verify a discrete element method (DEM) particle model of rototilled soil particles for investigating the particle migration and machine soil interaction mechanism when forming micro-ridge seed beds by the rapeseed direct seeding machine. The soil type was rototilled yellow-brown soil, which is widely distributed in the mid-lower Yangtze River. The study consisted of two parts: parameter calibration and application verification. The parameter calibration followed these steps: (1) testing the soil plastic limit and selecting the contact model accordingly; (2) measuring the basic parameters, such as the soil particle size distribution and repose angle after rototilling; (3) using the EDEM particle filling and particle factory function to reproduce the particle bed based on the particle size distribution; (4) solving the optimal contact parameter combination by using factorial design, steepest ascent method, and quadratic orthogonal rotation regression method. The application verification test used two sets of structural parameters of a rotary-cutting micro-ridge seedbed preparation device (RMSD, which is the key device of rapeseed direct seeding machine to forming micro-ridge seed beds) to conduct DEM simulation and field tests, and compared the particles migration patterns and the landform after operation. A soil plastic limit tester was used to determine the plastic limit of the soil. The plastic limit of the sampled soil was 24.79%, which is close to the upper limit of the moisture content for rototiller operation. Hence, the Hertze-Mindlin (no slip) contact model was selected. The particle size range and mass ratio of the rototilled soil particles from the rapeseed direct seeding machine were sieved and counted. The rototilled soil particles of each particle size range were scanned and modelled using the EinScan-Pro 3D scanner. Based on the 3D models of the soil particles, the EDEM particle filling function was used to reconstruct the particles with different particle sizes and mass ratios. The soil particles bed was re-generated in EDEM according to the particles` mass ratio. The contact parameter calibration test includes a two-level factorization test, steepest ascent test, and quadratic orthogonal regression test, respectively, to perform a preliminary analysis of test factors and eliminate non-significant tone system, narrow down the range of factors, and solve the combination of contact parameters. The contact parameter calibration test uses the repose angle as an indicator. The two-level factorization test showed that the impact restitution coefficient had no significant effect on the repose angle; the rolling friction coefficient, static friction coefficient, and the interaction term of the two significantly affected the repose angle. The steepest ascent test was designed based on the model regression equation from a two-level factorization test. The steepest ascent test reduced the range of factors tested 0.20-0.60 (static friction coefficient) and 0.05-0.40 (rolling friction coefficient) to 0.32-0.51 and 0.11-0.27, a reduction of greater than 50%, providing effective support for obtaining accurate regression models. Since the restitution coefficient had an insignificant effect on the repose angle, the impact recovery coefficient was set to an intermediate level of 0.350 for the quadratic orthogonal regression test. The calibrations resulted in restitution, static friction and rolling friction coefficients of 0.350, 0.351 and 0.257, respectively. The verification consists of simulations and field tests conducted on the RMSD with two structural parameters. The field verification test used the PIVlab tool and the Trimble TX8 3D laser scanner to obtain the soil particles` velocity and the landform. The simulation of 2 structural parameters was consistent with field experiments. The error of micro-ridge distance is 8.25%, which increases with the number of vanes of RMSD. The calibration parameters are accurate. This paper provides fundamentals for the DEM simulation and structural improvement for rapeseed micro-ridge seedbed preparation device.

The shovel type seedbed preparation machine is suitable for the preparation of rapeseed seedbeds in the rice-oil rotation area in the mid-lower Yangtze River. It can complete the functions of soil plowing, soil leveling, straw burying, and furrow opening in one operation. However, the unit had large vibration and noise during idling and field operations, which can easily cause wear and tear of key components, reduce work reliability and trouble-free working time, and affect the health and comfort of the driver. In order to solve the problem of large vibration during unit operation, this paper analyzed the theoretical excitation frequency of the main vibration source during the operation of the tractor coupling unit through theoretical calculation, and the vibration acceleration of the unit under idle speed and field operation conditions was tested by using Coco-80 dynamic signal Test and analysis system. By using time-domain analysis and frequency-domain analysis, the vibration acceleration at different measuring points under two working conditions was determined, and the main excitation source of the unit was the movement of the shovel type tillage and soil preparation device. Based on the results of the vibration test, a scheme to reduce the vibration of the shovel type seed bed preparation machine was proposed by optimizing the arrangement of the crank phase angle to reduce the combined inertial force and inertia moment of the machine. According to the mass substitution method and kinematics analysis, the inertial force variation trend of a single group of shovel tillage and land preparation devices was obtained. Base on the calculation results, it was further clarified that the inertial force on the whole machine can be reduced by rationally designing the crank phase angle arrangement of the ten groups of mechanisms of the unit. Based on the calculated inertia force on a single group of mechanisms and combined with the crank phase angle of the existing machine tools arrangement, the inertial force and inertial moment force models of ten sets of crank-rocker mechanisms of the whole machine were established, and the arrangement of the crank phase angle that minimizes the total inertial force and inertial moment of the whole machine was obtained by using MATLAB software. Under this crank phase angle arrangement, the total inertial force of the whole machine was basically balanced, and the average absolute value of the total inertia moment in the x and y axes were reduced by 37.40% and 30.09% respectively. In order to verify the vibration reduction effect of changing the crank arrangement on the unit, the acceleration time domain signal was collected from the improved unit at the place where the vibration was relatively large. Compared with the unit before improvement, the total vibration of the measuring points after the improvement was respectively reduced by 36.42% and 31.97% under the conditions of idle speed and field operation. This research can provide reference for the inertia force balance design of planar linkage mechanisms and the research on vibration reduction of agricultural machinery based on planar linkage mechanism groups.

Direct seeding has been one of the most efficient cultivation modes for a wide range of plants, such as rapeseed. Among them, the existing ditching device cannot fully meet the practical direct seeding in recent years, due to the low stability of the furrow shape and the seedbeds on both sides of the furrow. In this study, a propeller-type ditching device was designed to actively open the furrows at high speed (≥10 km/h) and simultaneously distribute the soil in the middle and lower reaches of the Yangtze River. A quasi-propeller ditching blade was then proposed, according to the working mode of propellers. The blade arrangement was determined using kinematic and dynamic analysis. The critical parameters (the pitch and edge structures) were also determined to reduce the cutting resistance. A simulation experiment of the blade cutting was carried out using the discrete element model of the blade cutter-soil system. The simulation results indicated that the cutting resistance first decreased and then increased with the increase of the pitch angle, whereas, the rear grinding edge reduced the soil cutting resistance. The quasi-propeller blade group with the optimal combination of pitch angle and edge structure achieved a resistance torque of 176.6 N·m and a traction resistance reduction of 447.7 N, compared with the straight spoon-blade group with a travel speed of 12 km/h and rotation speed of 810 r/min. The dynamic analysis was implemented to determine the curved structure parameters of the soil homogenizing plate. Furthermore, a soil-distributing simulation experiment was carried out using the ditching cutter-soil distributing plate-soil interaction model. The better performance of soil distributing was achieved, when the camber of the left and right distributing plates was 0.19 and the down-inclination angle was 10° and 7°, respectively. The field experiment indicated that the work quality of the overall device fully met the requirements of direct rapeseed seeding when operating at a high speed of 9-12 km/h. An optimal combination was achieved: the furrow depth was 169.1-188.6 mm, the furrow depth stability coefficient was 92.5%-95.6%, the flatness of the furrow surface was 22.2-23.0 mm, the coefficient of variation of soil distributing on both sides was 14.3% and 17.2%, and the stubble burying rate was 81.96%-87.46%, the operating power consumption at the operating speed of 12 km/h was 66.84 kW. This finding can provide a strong reference for the high-speed no-tillage, ditching, and high-quality seedbed preparation for rapeseed in the rice-oil rotation areas of the mid-lower Yangtze River.

Air-assisted centralized metering devices cannot fully meet the large-scale seed supply during high-speed operations in recent years. It is high demand for better compatibility in the seeding rate and size of rice, wheat, and rapeseed, particularly on the high flowability of rice and wheat. In this study, a type-hole wheel was proposed to specifically design for the compatible mode with rice, wheat, and rapeseed. The number and rotational speed of the hole wheels were rapidly adjusted to allow for the flexible seeding rate in the seeding system, leading to the simultaneous use of rice, wheat, and rapeseed. The spiral arrangement of the hole wheels was used to increase the mobility of seeds within the seed-filling area. Thereby, the stability of seed supply was improved during high-speed seed feeding operations. Mechanical analysis was also carried out on the seed filling, seed carrying, and seed falling stages during the seed supply process. The type-hole structure parameters were determined using the physical characteristics of rice and wheat seeds. A hole wall curve was designed using brachistochrone. EDEM simulation experiments were conducted to analyze the population motion states under different rotational speed conditions at the filling, carrying, and falling stages. The variation curves were derived for the number of seeds that were supplied in the spiral and linear arrangement of the hole wheel with time. The peaks, valleys, and periods of the curves were statistically analyzed. The EDEM simulation experiments show that better performance was achieved at 40 r/min for the rice, wheat, and rapeseed supply stages. There was more outstanding behavior of the dragging and bouncing during the seed-filling stage at 80 r/min. Some seeds cannot fully enter the mold hole during the initial stage of seed carrying. But the seeds were moved down the side wall of the mold hole for the secondary seed filling, as the mold hole wheel rotated. All seeds were fed in a timely manner without any "seed sticking" phenomenon during the seed-feeding stage. Once the number of holes was determined, the pulsation period was inversely proportional to the speed of the hole wheel. The adjacent holes were sequentially misaligned on the hole wheel, when the hole wheel was spirally arranged. The continuous seed filling and feeding performance were improved to reduce the pulsation, indicating a more stable seed supply. Furthermore, the fluctuation range was reduced by more than 30 grains in the spiral arrangement of the shaped hole wheel for the rice and wheat seeds under the same rotational speed conditions, compared with the linear arrangement. The bench test was carried out to determine the rotation speed range with the better seed supply rate and stability. The regression model of seed supply rate was constructed for the rice, wheat, and rapeseed. Therefore, the coefficient of variation was less than 1% for the stability of the seed supply rate, and the seed supply rates were 1 050.62-1 535.87, and 4 171.82-5 073.76 g/min, respectively, for the hybrid rice and wheat seeds, when the number of type-hole wheels was 16, and the speed of seed supply ranges were 30-50, and 50-70 r/min, respectively. In rapeseed, the coefficient of variation was less than 0.5% for the seed supply rate stability, and the range of rapeseed supply rate was 160.42-227.45 g/min, when the number of type-hole wheels was 1, and the rotational speed of seed supply was 20-30 r/min. Moreover, there was a relative error of less than 2% between the regression model and the experimental value of the seed supply rate of rice, wheat, and rape. The field seeding experiment showed that the stability coefficients were 1.32%, 1.16%, and 1.07% for the variation of the total displacement in the collector for the rice, wheat, and rapeseed, respectively when the operating speed was 8-10 km/h. The seeding system fully met the high requirements for the multi-crop seeding operations with the rice, wheat, and rapeseed. This finding can provide a strong reference to optimize the structural parameters of the air-assisted centralized metering device for multiple crops.

Transplanting offers several advantages, such as alleviating the conflict of crop rotation, shortening the growth cycle of rapeseed, and increasing the unit yield of rapeseed. However, in the rice-rapeseed planting pattern, the growth period of rapeseed is short, manual transplanting is labor-intensive, and there is a lack of mechanized transplanting technology and equipment for rapeseed bare-root seedlings. To address these issues, this study proposed a mechanical transplanting process scheme of "leveling the ridge surface + furrowing and soil gathering + aligning and placing seedlings + soil covering and compacting" based on the agronomic requirements for rapeseed transplanting and the morphological characteristics of rapeseed bare-root seedlings. Meanwhile, a transplanter for rapeseed bare-root seedlings had been developed. The structure and working principle of the transplanter were elaborated. Structural design and theoretical analysis were carried out for key components such as the spiral soil homogenizer, trenching soil aggregating device, row-aligned seedling placement device, and soil covering and compaction device. According to the degree of freedom constraints during the conveying process of rapeseed bare-root seedlings, morphological characteristics, compatibility analysis with each key component, and the quality requirements for each transplanting operation, the key structural and working parameters of the transplanter were determined. The spiral soil homogenizer, with a pitch of 180 mm, a pitch angle of 64°, and a blade diameter of 200 mm was designed. When the furrowing disc inclination angle, center distance, and penetration depth were 42.1°, 350 mm, and 70 mm respectively, the requirements for preparing a seedling furrow with a width of 170 mm can be met, and at this time, the height of the gathered soil in the middle was 107.2 mm. A mechanical and kinematic model for the lateral sequential feeding and vertical flexible clamping conveying process of rapeseed bare-root seedlings was established. The conditions for stable seedling feeding and "zero-speed seedling dropping" were analyzed. The internal spacing of the partition, initial clamping spacing, clamping conveying inclination angle, and seedling dropping height were determined to be 45 mm, 30 mm, 70°, and 165 mm respectively. The rotational speeds of the first and second driving pulleys were 15-32 mm/s and 155-230 mm/s respectively. The covering disc inclination angle and soil turning depth were analyzed and determined to be 40° and 160 mm respectively, and the compaction wheel thickness and installation inclination angle were 60 mm and 10° respectively. A method for field tests and performance evaluation was proposed, and field transplanting performance tests had been completed. The results of the field tests showed that when the machine advances at a speed of 0.80-1.20 km/h, the inclination angles of the furrowing disc and covering disc were 42° and 40° respectively, and the rotational speeds of the first and second driving pulleys were 20 and 160 r/min respectively, there was no missed transplanting during the transplanting operation. The seedling placement success rate was 93.63%, the seedling injury rate was 3.21%, the planting qualification rate was 90.25%, and the coefficient of variation of plant spacing was 9.01%. All key components of the transplanter operated stably and can completed functions such as ridge surface leveling, seedbed preparation, seedlings alignment and placement, and soil covering and compaction in a single pass. All operational performance indicators met the basic requirements for the mechanized transplanting of rapeseed bare-root seedlings. The growth of rapeseed after transplanting was tracked. The survival rate was counted three days after transplanting and reached 96.52%. This study provided a new approach for the development of mechanized transplanting equipment for bare-root seedlings of leafy and stem vegetables. The findings and the developed transplanter could potentially enhance the efficiency and quality of rapeseed transplanting operations, contributing to agricultural productivity and sustainability in regions where the rice-rapeseed planting pattern is prevalent.

Existing micro-ridge seedbed preparation devices can often be equipped with conventional rotary tillage. However, the shallow tillage depth has been confined to the suboptimal operational efficiency. Particularly, the rapeseed cannot resist extremely adverse climates during optimal sowing and seedling in the current cultivation. In this study, a shallow plow was proposed with the high-speed micro-ridge direct seeding for rapeseed. Three sequential functions were integrated: 1) high-speed strip shallow tillage. A "lift-first and throw-later" mechanism was utilized to rapidly form the ridges using directional soil throwing; 2) micro-ridge seedbed shaping. The geometric configuration of the ridges was optimized to enhance the soil structure, and 3) sowing on ridge tops and furrows. The moisture was regulated to improve the stress resilience and yield stability of the rapeseed in the micro-ridge system. According to the operational requirements of the high-speed strip shallow tillage, a directional soil-throwing shallow plow was developed for the soil displacement at high speed. The micro-ridge morphology was analyzed for the curved surface of a variable-pitch twisted spiral plow body. The plowshare parameters were then determined: a cutting-edge angle of 120°, an entry angle of 30°, and a plowshare width of 120 mm. A mathematical model was established for the shallow plow guide curve. A kinematic analysis was also conducted on the soil lifting and throwing. Single-factor experiments were performed using EDEM software. A systematic investigation was also made on the effects of the shallow plow height, shallow plow opening, and end helix angle on the directional soil-throwing performance. A central composite design (CCD) with two factors (shallow plow opening and end helix angle) and five levels was implemented to determine their interactions on the directional soil-throwing performance. The optimal combination of the parameters was identified after iterative simulation and optimization: the shallow plow height of 375 mm, shallow plow opening of 200 mm, and end helix angle of 40°. Field experiments were conducted on the sandy clay loam and loam soil. The shallow plow achieved better soil-throwing performance at the high speed (12 km/h), compared with the conventional speed (4 km/h). Furthermore, the directional soil throwing was enhanced under the high-speed operation. There were well-defined furrows and strip-shaped soil accumulation in ridging zones. Key metrics included a soil flow back ridge-furrow ratio of 26.18%, a soil-directed migration ratio of 57.42%, and a soil throw accumulation height of 160.60 mm. The better operational passage of the machined to the stable ridge with a ridge height of 148.64 mm and a ridge width of 349.6 mm. The coefficients of variation were less than 5% for the ridge height and width. The high stability was also achieved in the directional soil throwing position, soil quantity, and throwing accumulation height, thus fully meeting the micro-ridge requirements. Furthermore, directional soil-throwing with the shallow plow can be expected for optimal operational passage in the high-speed micro-ridge seedbed preparation. Seedling emergence validated that the micro-ridge seedbed configuration fully met the agronomic requirements for the rapeseed direct-seeding. These findings can provide a viable technical pathway to develop high-quality rapeseed seedbeds for micro-ridge direct seeding.