Sticky clay soil has presented significant challenges to mechanized rapeseed planting in the rice-oil rotation regions of the middle and lower reaches of the Yangtze River. Conventional profiling mechanisms often struggle to maintain consistent bed shaping, leading to severe soil adhesion, gully formation, and clogging of the machinery. The stability of seeding depth is also limited to uneven seedbed surfaces, water accumulation, and waterlogging stress. There is high demand for the overall quality of rapeseed. In this study, the anti-adhesion mechanism of the whole profiling device was designed to fully meet the agronomic and mechanical requirements. A systematic investigation was conducted to determine the rotary compressing and shaping for the overall bed profiling. Mechanical-soil interaction of the rotary compaction was analyzed during the operation of a passive (non-driven) rotary roller. There was a decrease in the contact surface between the roller surface and the soil as the contact pressure increased, leading to inevitable soil accumulation and difficult detachment. In contrast, an active (driven) rotary roller was generated into the relative velocity difference between its surface and the seedbed. The bed was formed to exert a shearing and squeezing action on the roller surface in the forward rotation, leading to an active anti-adhesion mechanism. Conversely, the unformed soil on a reverse rotation roller was utilized to scour the roller surface—effectively preventing adhesion—the opposing motion and excessive grinding force tended to induce defects, such as surface cracks on the seedbed. A coupled DEM-MBD simulation was conducted to determine the velocity, displacement, and kinetic energy of soil particles adhered to the active roller. The microscopic interaction was visualized after simulation. As such, the soil adhesion primarily initiated in the contact zone with the unformed and loose soil, whereas the active anti-adhesion effect predominantly occurred in the contact zone with the compacted and formed bed. Subsequently, the bench tests were conducted to verify the simulation. In the forward-rotating roller, the soil adhesion area, adhesion volume, and bed surface roughness followed a trend of initially increasing and then decreasing as the rotational speed increased. Notably, the low anti-adhesion performance was found at the speed ratio of near 100% (where the linear velocity matched the forward speed). Therefore, the passive roller demonstrated low performance in both anti-adhesion and shaping quality. Furthermore, orthogonal bench tests were conducted to optimize the parameters, with the roller speed and absolute soil moisture content as experimental factors. The evaluation indices included the adhesion area, adhesion volume, and bed surface roughness. Results showed that the adhesion decreased with the high speeds of the reverse-rotating roller, whereas the bed surface roughness increased significantly, due to soil disturbance. The performance of adhesion depended on both rotational speed and soil moisture. Crucially, the forward-rotating roller demonstrated the superior adaptability to the variations in soil moisture content, compared with the other configurations. Finally, field trials were conducted in the post-rice stubble fields with sticky soil (absolute water content >30%). The forward active rotary roller was achieved in a soil adhesion area of 62.4 cm² and an adhesion mass of 174 g, which reduced the adhesion of 90.05% and 87.77%, respectively, compared with the passive roller. The bed surface roughness was recorded at 15.7 mm, which was improved by 86.08% over the passive counterpart. In contrast, the reverse-rotating roller also caused the excessive grinding of the bed surface. The forward-rotating active profiling mechanism can be expected for sticky soils. The finding can provide a strong reference for designing the seedbed preparation equipment in the Yangtze River basin.

A pneumatic seed metering device is required for the high speed and intelligent variable operation in recent years. However, the existing complicated transmission and pneumatic system and mechanical structure cannot fully meet the large-scale production of pneumatic supply with the high stability, due mainly to the pressure loss caused by a curved pipe. In this study, the invention problem problem-solving theory (TRIZ) and axiomatic theory design (AD) methods were applied to carry out the innovative design of a pneumatic seeding device for rapeseed. Firstly, the seeding maturity prediction and evolution were used to clarify the development stage, evolution path, and potential of seed metering using TRIZ technology. The existing seeding technology was in a recession recovery period, while the evolution of the technology system was in line with the S-curve evolutionary law and evolutionary model. The future seed metering device was preferred for the integration in the simple, microscopic, controllable, and automated evolutionary path. Secondly, the design process model was established using the integration of TRIZ and AD. TRIZ tools were introduced in the process of mapping functional to structural domains. Among them, the "conflict resolution principles" was adopted to solve the contradiction and conflicts of the transmission and pneumatic systems in the existing seed metering device. The invention principles were selected to optimize the structural parameters. Finally, the motor was utilized to directly drive the seeding disk and the built-in air chamber of the fan. The original design matrix was developed using independent design axioms and the minimum entropy. An innovative system was designed to integrate the motor- fan with the pneumatic seed metering device for rape. The trial production and processing were performed on two technical implementation schemes. The motor fan was determined to arrange on the same side after optimization, particularly for the better airtightness and structural stability. The integrated motor drive was used to simplify the transmission, whereas, the integrated fan was to eliminate the gas transmission pipe, in order to reduce the wind pressure loss. As such, the improved transmission and pneumatic system were required only a small space without the additional power. The test results show that the integrated seed metering device was fully meetmet the requirements of single seed metering. A better performance was achieved in the qualified index is more than 90%, even reached reaching up to 99.82%, when the absolute value of suction negative pressure was 1.0-2.0 kPa and the working speed was less than 7 km/h. The required pressure for the qualified index of 90% was lower than before. The innovative design of the pneumatic seed metering device was integrated the power and pneumatic sources, which was were in the line with the technological system evolution path, individual start and stop of the seeding unit without any influence on the rows. More importantly, the mechanical structure and transmission were better matched for the development trend of intelligent variables. This finding can provide an innovative design idea and references for the design of a pneumatic seed device.

An appropriate fertilizer application can be one of the most important indicators for resistance to the downfall and high yield of direct sowing rape. Among them, the fertilizer placement and application rates can dominate the root and plant growth, development, and lodging resistance of winter rapeseed. This study aims to investigate the effects of the different ratios of layered fertilization in the deep and shallow layers under the precision combined seeder on agronomic characteristics, such as the root growth, plant resistance to lodging, and yield of rapeseed. The agricultural machinery and agronomic techniques were integrated to further improve the mechanical application fertilization of winter rapeseed. "Huayouza 62" rapeseed variety was selected as the test crop at the fertilization rate of 600 kg/hm². The control group was taken as the side deep fertilization of CK1 on the 10 cm positioning under the seed, and the shallow layer mixing fertilization of CK2. Three treatments of deep fertilization were set as the shallow and deep layer fertilization ratios of 1:3 (FL), 1:1 (FM), and 3:1 (FH) experimental groups. A total of five fertilization treatments and field trials were conducted in 2020 and 2021. The experiment site was located in the winter rapeseed area in Jingzhou, Hubei Province in the middle reaches of the Yangtze River basin. A measurement was performed on the root growth characteristics, soil firmness, shoot fresh weight, stem bending resistance and yield of rapeseed during the harvest period. A systematic analysis was then made on the five treatments, in terms of the root distribution, soil penetration resistance of topsoil, lodging index, and yield of rapeseed. The results showed that the layered deep fertilization significantly promoted the root downward migration and the root architecture of rapeseed. The average values of root surface area, root volume, root dry weight, and taproot length were 1.58, 1.47, 1.29, and 1.16 times higher than those in the CK1 treatment, while 3.63, 2.79, 1.46, and 1.28 times higher than those in the CK2 treatment, respectively. Meanwhile, the average soil penetration resistance decreased by 4.91% and 15.25%, respectively, compared with the CK1 and CK2 treatments. The overall performance was ranked in the descending order of the FM > FH > FL, in terms of the taproot length, root surface area, root volume, and root dry weight in the different layered fertilization treatments. The rape plant of root stem diameter, lodging angle, and fracture resistance of the FH treatment were 1.11, 1.25, and 1.31 times higher than those of the FM treatment. The lodging index decreased by 26.90% on average, but the field lodging angle increased by 25.14%, compared with the FM treatment. The yield, number of branches per plant, number of corner fruit, and thousand-grain weight of layered deep fertilization treatment were significantly higher than those of positioned deep fertilization and mechanical mixing fertilization treatment. the average rapeseed yield of FM treatment increased by 9.85%, 16.35%, 26.88%, and 37.75%, respectively, compared with the FL, FH, CK1, and CK2. The root distribution, soil penetration resistance, lodging index, and grain yield of winter rapeseed were considered under different fertilization treatments. The FM treatment was achieved in the better optimal fertilization for the high yield and lodging resistance of field mechanized direct sowing winter rapeseed.

The low utilization rate of agricultural machinery can be caused by the fragmented and scattered farmland plots with the diverse planting patterns in southern China. In this study, a single-seed precision seed-metering device was developed with a pneumatic roller for multiple crops using theoretical analysis and bench tests. Maize and rapeseed were selected as the experimental subjects due to their significant morphological differences. A systematic evaluation was also performed on the device's adaptability. The overall structure and working performances of the device were highlighted to combine the positive and negative air pressure for the precise seed metering. The structural parameters of the seed-metering hole wheel were determined according to the normal distribution in the triaxial dimensions of the seeds. The seed-metering wheel was equipped with the spoon-shaped holes (with a diameter of 130 mm) that were tailored to each crop. Specifically, the hole dimensions were as follows: The length of 2.5 mm, the width of 2.4 mm, the depth of 1.8 mm, the suction hole diameter of 1.3 mm, the spoon head radius of 1.7 mm, the angle between the spoon tail and the horizontal direction of the suction hole was 45° for rapeseed, while the length of 15 mm, the width of 14 mm, the depth of 8.5 mm, the suction hole diameter of 4.3 mm, the spoon head radius of 7 mm, and the angle between the spoon tail and the horizontal direction of the suction hole was 30° for maize. The mechanical analysis was conducted on the seed-filling, seed-carrying, and seed-throwing. The relationships between these processes and key parameters were established, such as the air pressure and the structure of holes. Furthermore, the performance was optimized for the forces acting on seeding. Single-factor experiments identified the optimal working ranges for the suction negative pressure and rotational speed. The suction negative pressure of maize was 3-5 kPa, and the rotation speed was12-20 r/min. In this range, the qualified index of maize seeding could reach 94.88%, and the minimum values of multiple index and leakage index were 2.70% and 0.99%, respectively. The negative pressure of rapeseed suction was 1.1-1.9 kPa, and the rotation speed was 15-35 r/min. In this range, the qualified index of rapeseed seeding could reach 96.4%, and the minimum values of multiple index and leakage index were 1.11% and 1.02%, respectively. The results demonstrated that the performance of the device was achieved with high precision under diverse operating conditions. A two-factor five-level orthogonal rotation experiment was also conducted to further refine the operational parameters. Variance analysis was then used to verify the optimization. Three-dimensional response surfaces were generated using Design-Expert software. There were relationships between working negative pressure, rotational speed (experimental factors), and the qualified, multiple, and leakage index (evaluation metrics). In the corn qualification index above 94%, the stable working range was negative pressure 3.3-3.7 kPa and rotational speed 13-16 r/min. In the rapeseed qualification index above 94%, the stable working range was negative pressure 1.2-1.8 kPa and rotational speed 18-30 r/min. In maize, the qualified index was 95.63%, the multiple index was 3.52%, and the leakage index was 0.85% at a rotational speed of 13 r/min (forward speed ≈ 3.6 km/h) and suction negative pressure of 3.3 kPa. In rapeseed, the qualified index was 95.60%, the multiple index was 2.92%, and the leakage index was 1.48% at a rotational speed of 23 r/min (forward speed ≈ 3.4 km/h) and suction negative pressure of 1.50 kPa. A modular seed-metering device was developed for the single-seed precision seeding compatible with both large and small seeds. The finding can provide a strong reference to improve the quality of mechanized sowing. Technical support can also be offered for the multi-purpose use of a single machine under diverse planting patterns in the clay-heavy soils of southern China.

To address the problem that granular compound fertilizer is prone to agglomeration during mechanized direct seeding of oilseed rape in the middle and lower reaches of the Yangtze River, which causes clogging of the fertilizer discharger and leads to a reduction in the uniformity and stability of fertilizer discharge, research on the crushing mechanism of caking compound fertilizer was performed. Considering that it is difficult to measure the bonding force between caking fertilizer particles directly, a simulation model of caking composite fertilizer was established with the bonding model in EDEM discrete element software. To decrease error between the simulation and physical test results, the normal contact stiffness, tangential contact stiffness, critical normal stress, critical tangential stress, bonding radius, and other parameters of the bonding model of caking composite fertilizer were calibrated. The three-dimensional structure of the caking composite fertilizer was obtained via three-dimensional scanning, the critical crushing displacement and critical crushing force of the caking composite fertilizer were measured via compression testing with a mass spectrometer, and the optimal parameter combination of the bonding model was determined via EDEM discrete element simulation of the Plackett-Burman test, steepest ascent test, and Box-Behnken test. The results of the simulated compression tests under the optimal parameter combination show that the relative errors of the critical crushing displacement and critical crushing force with respect to the physical test results were 0.296% and 0.343%, respectively. Using the crushing rate of caking compound fertilizer as an evaluation index, the feasibility of the calibrated parameters was verified for a four-head spiral two-row fertilizer discharger installed in a direct seeding machine for oilseed rape. The results show that the relative errors of the caking fertilizer crushing rates from the simulation relative to those of the bench and field tests were 5.81% and 5.06%, respectively, indicating that the calibration parameters of the discrete element model were accurate and could be used for parameter analysis of caking fertilizer with a discrete element model. These results can provide a reference for the structural optimization of fertilizer discharger crushing of caking fertilizer of direct seeding machine for oilseed rape.

A seed metering device is often equipped with a combination of positive and negative pressure in the planter for rapeseed. The chaotic seeds can be discharged via negative pressure suction seed and positive pressure blowing seed in a uniform and orderly manner. However, the orderly state of seed flow is easy to be broken in the process of seed guiding, resulting in unsuitable seed spacing. It is very necessary to clarify the seed guiding process for the higher seeding quality. This study aims to theoretically analyze the influence of structural seed tubes on the orderly state of seed flow. It was found that the main reason for the damage to the orderly state of seed flow was the random collision between seeds and seed tubes in the seed guiding. The influencing factors on the collision were the curve, inner diameter, and length of the seed tube. A simulation test was then carried out on the movement of seeds in the seed tube. Once the more linear curve of the seed tube was, and the thicker inner diameter was, the smaller number of collisions was, and the shorter time of passing through the seed tube was. Specifically, the coefficient of variation was reduced by 2.1 percentage points for the collision number of seeds through the seed tube with the linear-shaped curve in the same inner diameter and length, compared with the S-shaped curve. The coefficient of variation of time was reduced by 1.8 percentage points on average. Compared with the parabola-shaped curve, the coefficient of variation of collision number was reduced by 0.5 percentage points on average, and the coefficient of variation of time was reduced by 0.5 percentage points on average. The coefficient of variation of collision number of seeds was reduced by 7.2 percentage points through 32 mm seed tube in the same curve and length, compared with 25 mm, and the coefficient of variation of time was reduced by 2.6 percentage points. The simulation test showed that the larger the coefficient of variation of the collision times of seed flow through a seed tube was, the larger the coefficient of variation of time was, the more discrete the seed flow trajectory was, and the worse the orderly state of seed flow was. Therefore, there was less influence on the orderly state of seed flow in the curve of the seed tube, compared with the inner diameter and length. The bench test was consistent with the simulation. Compared with the S-shaped curve, the qualified index of seed spacing of the linear-shaped curve increased by 3.2 percentage points on average, the missing index and the multiple index decreased by 2.0 and 1.2 percentage points, respectively. Compared with the parabola-shaped curve, the qualified index of seed spacing of the linear-shaped curve increased by 2.8 percantage points, the missing index and the multiple index decreased by 2.0 and 0.8 percentage points, respectively. Compared with 25 mm, the qualified index of seed spacing of 38 mm seed tube increased by 11.4 percantage points, the missing index and the multiple index decreased by 4.6 and 6.8 percentage points, respectively. Compared with 80 cm, the qualified index of seed spacing of 20 cm seed tube increased by 27.6 percantage points, the missing index and the multiple index decreased by 10.6 and 17.0 percentage points, respectively. In addition, the frequency distribution of the time interval gradually changed from normal distribution with relatively uniform interval to exponential distribution with the increase of the multiple index, when the inner diameter decreased or the length increased. The optimal seed guiding was achieved, where the inner diameter of the seed tube should not be less than 25 mm, whereas, the length should not be more than 40 cm. This finding can provide a strong reference for the subsequent development and optimization design of seed tubes.

The accurate location of targets can greatly contribute to the precision operations within agricultural scenes. Binocular stereo vision can be used to obtain the three-dimensional (3D) perception of the real world. Considerable application potential can depend mainly on the 3D localization and point cloud reconstruction of targets in agricultural environments. This study aims to review the latest research on binocular stereo vision and its applications in the agricultural field. Firstly, the pipeline of binocular stereo vision was summarized, including binocular camera calibration, epipolar rectification, and stereo matching. The binocular camera was utilized to calculate the depth of targets using disparity data. The objective of stereo vision calibration was then to determine the intrinsic and extrinsic parameters of the camera, including reference calibration, active vision calibration, self-calibration, and neural network calibration. A mapping was also established among points in pixel and world coordinates. In epipolar rectification, the constraints were employed to reduce the search space, in order to match the points from two dimensions to one. Stereo matching was used to calculate the disparity, in order to match the left and right images in both feature-based and deep learning. Furthermore, the local, global, and semi-global methods were categorized in the search range of matching pixels. The local method was used to search for the matching points within surrounding areas, the global method was to minimize the global energy function, and the semi-global method was to aggregate the costs from various directions. In contrast, more complex features were learned to enhance the stereo matching using deep learning. The network frameworks were introduced, such as convolutional neural networks (CNN), generative adversarial networks (GAN), transformers, neural architecture search (NAS), iterative optimization (IO) and graph neural network (GNN). CNNs performed extensive convolution operations to compute the matching costs for high accuracy, including convolutional encoders and decoders, hierarchical pyramids, as well as complex cost volumes. GANs synthesized the data through adversarial generation, in order to acquire the realistic disparity in binocular datasets. In Transformer, the self-attention mechanisms were utilized to capture the contextual information, indicating the limitations of CNN receptive fields. In NAS, the stereo-matching network architectures were automatically constructed to incorporate the human prior knowledge, in order to removal the peripolar need for manual design. The IO with no requirements on the construction of cost volumes and aggregation, leading to significant resource savings for the large ranges of disparity. GNN was used to simulate the complex relationships among features, and then extract the global information. Furthermore, the number and impact of publications were analyzed to examine the widespread applications of binocular stereo vision in agricultural research. The latest applications were explored from the recent literature. As such, 3D localization of fruit targets facilitated map navigation in practical operations using point cloud processing. The technology also supported the 3D reconstruction of crops or the segmentation of individual organs for growth parameter measurement. Additionally, the crop diseases or pests were identified to combine with precision spraying by agricultural machinery. Ultimately, the challenges were summarized to apply the binocular stereo vision to agriculture. The high precision was demonstrated in the localization, measurement, and identification. Some issues still remained, such as model complexity, scene limitations, scarcity of datasets, and fewer evaluation standards for stereo matching. Looking ahead, future research should focus on the algorithm design and optimization, the intelligent assistance platforms, the comprehensive datasets, and the evaluation system, in order to enhance the practicality and efficiency of binocular stereo vision systems in precision agriculture.

The relationship between the parameters of the bonded-particle model and the macroscopic properties of oilseed rape shoot stalk provides valuable insights into the interaction between the stalks and harvesting machinery. In this study, a discrete element model of oilseed rape shoot stalk was constructed using a method that combined ordered and bimodal distribution filling. The model’s six contact and five bonding parameters were calibrated based on physical and simulated diametral compression tests. The Plackett-Burman design was employed to screen the effects of the parameters on the rupture force. The range of significant parameters was determined using the steepest ascent test. Furthermore, by calculating the second-order regression model and analyzing the significance of parameter combination using the central composite design method, the optimal parameter combination was identified, including a bonded disk radius of 0.78 mm, a normal stiffness per unit area of 4.61×10⁷ Pa, a shear stiffness per unit area of 5.21×10⁷ Pa, and a coefficient of static friction between particles of oilseed rape shoot stalk of 0.47. The simulated rupture force (58.80 N) differed by 6.5% from the average value of the physical test (62.92 N), and the deformation of the compression process was consistent. The results demonstrate that the model effectively reflects the mechanical failure properties of oilseed rape shoot stalk during the diametral compression, providing a reference for modeling other crop stalks and aiding in the study of interactions between clamping-transporting devices and stalks during harvesting.

Oilseed rape is an important oilseed crop planted worldwide. Maturity classification plays a crucial role in enhancing yield and expediting breeding research. Conventional methods of maturity classification are laborious and destructive in nature. In this study, a nondestructive classification model was established on the basis of hyperspectral imaging combined with machine learning algorithms. Initially, hyperspectral images were captured for 3 distinct ripeness stages of rapeseed, and raw spectral data were extracted from the hyperspectral images. The raw spectral data underwent preprocessing using 5 pretreatment methods, namely, Savitzky–Golay, first derivative, second derivative (D2nd), standard normal variate, and detrend, as well as various combinations of these methods. Subsequently, the feature wavelengths were extracted from the processed spectra using competitive adaptive reweighted sampling, successive projection algorithm (SPA), iterative spatial shrinkage of interval variables (IVISSA), and their combination algorithms, respectively. The classification models were constructed using the following algorithms: extreme learning machine, k-nearest neighbor, random forest, partial least-squares discriminant analysis, and support vector machine (SVM) algorithms, applied separately to the full wavelength and the feature wavelengths. A comparative analysis was conducted to evaluate the performance of diverse preprocessing methods, feature wavelength selection algorithms, and classification models, and the results showed that the model based on preprocessing-feature wavelength selection-machine learning could effectively predict the maturity of rapeseed. The D2nd-IVISSA-SPA-SVM model exhibited the highest modeling performance, attaining an accuracy rate of 97.86%. The findings suggest that rapeseed maturity can be rapidly and nondestructively ascertained through hyperspectral imaging.