In view of the problems of the inability to continuously adjust the seeding rate, small adjustment range, and low precision of the rice direct seed-metering device, a variable capacity roller-wheel seed-metering device was designed, fabricated, and verified. With the variable capacity method, the seeding rate could be adjusted steplessly and with high precision through the seeding rate adjusting mechanism. Meanwhile, theoretical analysis and parametric design of the critical components, such as the seeding wheel and the seeding rate adjusting mechanism, were carried out. The rotation speed of the seed-metering device, the sphericity of rice seeds, and the adjustment depth were selected as the main influencing factors of the experiment. Then, the full-factor experiment was conducted, and the results of the bench validation experiments showed that the average seeds per hill error of the seed-metering device could be controlled within 2%. Meanwhile, the seed-metering device performed the best when the rotation speed of the seed meter device was 30 r/min, the sphericity of rice seeds was 52.7%, and the hole depth was 6 mm. Compared to the conventional mechanical precision seed-metering device, the designed seed-metering device offered better seeding performance. The research results provide theoretical and practical references for the design of a rice seed-metering device and the development of precision agriculture.

To improve the expandability, seeding accuracy, and operating speed range of the electric drive system (EDS) of precision seeders, this study constructed an EDS based on a controller area network (CAN) bus and designed a motor controller based on a field-orientated control (FOC) algorithm. Full-factorial bench and field tests based on seed spacing (0.1, 0.2, and 0.3 m) and operating speed (3, 6, 9, 12, and 15 km/h) were carried out to evaluate the performance of the EDS. The results of bench tests showed that seeding quality varied inversely with operating speed and positively with seed spacing. The average quality of feed index (QFI) at 0.1, 0.2, and 0.3 m seed spacing in bench tests was 88.38%, 96.67%, and 97.36%, with the average coefficient of variation (CV) being 20.13%, 16.27%, and 13.20%. Analysis of variance confirmed that both operating speed and seed spacing had a significant effect on QFI and CV (p < 0.001). The analysis of motor rotational speed accuracy showed that the relative error of motor rotational speed above 410 rpm did not exceed 2.24%, and the relative error had less influence on the seeding quality. The average QFI was 85.93%, 95.91%, and 96.24%, with the average CV being 21.12%, 15.50%, and 16.49% at 0.1, 0.2, and 0.3 m seed spacing in field tests. The methods and results of this study can provide a reference for the design and optimization of the EDS in a maize precision seeder and provide an effective solution for the improvement of maize yields.

This study develops a novel electric-driven metering device to address the mismatch between the seeder rotation speed and vehicle speed in traditional mechanical precision hill direct-seeding metering devices for rice, which is caused by wheel slippage. The device integrates a Global Navigation Satellite System (GNSS) speed measurement module and an optimised incremental Proportional-Integral-Derivative (PID) control algorithm, enabling precise seeding through electric drive. A multidisciplinary collaborative design approach is employed, and field experiments are conducted to evaluate the performance of the novel device under conditions of vehicle speeds ranging from 3 to 5 km/h, theoretical hill spacings of 0.15–0.25 m, and seeding rate adjustment positions of 1/3–1. The experiments use two rice varieties, “Longken 2021” from the northern rice growing region and “Jingliangyou Huazhan” from the southern rice growing region. The results demonstrate that the novel electric-driven metering device significantly outperformed the traditional mechanical device in terms of seeding precision, hill formation performance, and seeding rate accuracy. The novel device achieves a qualified rate of seeds per hill of 90.54%, with seedling omission and seed damage rates reduced to 4.98% and 0.69%, respectively. The hill diameter qualification rate increases to 95.21%, with no empty hills observed. The coefficient of variation of seeds per hill is maintained at 21.98%, meeting the agronomic requirement of 2–12 seeds per hill for conventional rice. However, for seeds with high moisture content and poor flowability (soaked seeds), the seed damage rate increases slightly by 0.47 percentage points. This study provided an efficient and reliable technical solution for the intelligent upgrading of precision rice direct-seeding equipment.

A critical challenge in the design optimization of subsoiling and deep-fertilization implements for root pruning during the regreening stage of winter wheat lies in the lack of a validated root–soil discrete element (DEM) model. This study analyzed and measured the geometric morphology of winter wheat root systems in soil during the regreening stage and constructed corresponding geometric models. Based on the DEM framework, a Hertz–Mindlin with bonding model (HMBM) for the wheat root system was developed. The parameters of this model were calibrated using Plackett–Burman (PB) and Box–Behnken design (BBD) methods. Soil particles were simplified to spherical shapes according to particle size distribution analysis, and a discrete element model of soil particles using the Johnson–Kendall–Roberts (JKR) contact model was established. Soil model parameters at three different moisture contents were calibrated with the angle of repose (AOR) as the target response. The accuracy of the root bonding model and parameters, as well as the root–soil contact model and parameters, was verified through pull-out tests and corresponding DEM simulations of single roots in soil. Comparison between experimental and simulated pull-out results confirmed the validity of the developed root–soil DEM model for winter wheat during the regreening stage. This study provides a solid theoretical and experimental basis for future research on root cutting and tillage operations in winter wheat.