To address the challenges in precision seeding of Cyperus esculentus L. seeds caused by their irregular shape and uneven surface, this study investigates the effect of soaking pretreatment on seed germination and adopts rubber-based seed suction holes to improve adsorption performance. Subsequently, calibration and experiments on discrete element simulation parameters were carried out. Initially, by setting four soaking time gradients (0, 24, 48, and 72 h), the optimal soaking duration was determined. Furthermore, through free-fall collision tests, static friction tests, and rolling friction tests, combined with the Plackett–Burman design, steepest ascent experiments, and Box–Behnken response surface methodology, the contact parameters between seeds and between seeds and rubber suction holes were calibrated and optimized. The results showed that the static friction coefficient (D) between seeds, the rolling friction coefficient (E) between seeds, and the rolling friction coefficient (H) between seeds and rubber have significant effects on the stacking angle. The optimal parameter combination obtained was D = 0.592, E = 0.325, H = 0.171. Validation tests on the dynamic stacking angle demonstrated that the relative error between the simulated and physical test values was only 1.89%, confirming the accuracy of the parameters. This study provides reliable parameter references for the design and simulation optimization of precision seed metering devices for C. esculentus after soaking pretreatment.

The seeds of Cyperus esculentus L. exhibit an uneven surface and irregular shape, which adversely affect precision seeding. Pre-sowing seed soaking treatment not only improves seeding performance, but also enhances the germination capability of C. esculentus seeds. However, the intrinsic parameters of the seeds undergo significant changes after soaking in terms of their physical properties, such as volume, weight, and density. These changes directly influence the fluidity and positioning accuracy of the seeds during the seeding process. Additionally, contact parameters, such as the coefficient of friction and the contact area between the seeds and the seeding apparatus, are altered by soaking. These parameters are crucial for designing efficient seeding devices. Therefore, it is necessary to measure the intrinsic parameters of soaked C. esculentus seeds and their contact parameters with the seeding apparatus to provide parameter support for the precision seeding analysis of pre-soaked C. esculentus. This study focuses on the calibration and experimental investigation of discrete element parameters for soaked C. esculentus seeds. Free-fall collision tests, static friction tests, and rolling friction tests were conducted to calibrate the contact parameters between soaked C. esculentus seeds and between the seeds and steel materials. Using Design-Expert, Plackett–Burman tests, steepest ascent tests, and Box–Behnken response surface tests were designed to obtain the optimal parameter combination for the C. esculentus contact model. The optimal parameters were validated through angle of repose simulation tests and physical experiments. The results indicate that the rolling friction coefficient (F) between seeds, the static friction coefficient (E) between seeds, and the rolling friction coefficient (J) between seeds and steel plates significantly affect the angle of repose. The optimal combination of discrete element parameters is as follows: the static friction coefficient (E) between seeds is 0.675, the rolling friction coefficient (F) between seeds is 0.421, and the rolling friction coefficient (J) between seeds and steel plates is 0.506. Using the calibrated parameters for simulation, the average angle of repose was 32.31°, with a relative error of 1.1% compared to the physical experiments.

The unique material properties of Cyperus esculentus L. seeds present challenges for precision seeding, as no specialized seed-metering device is currently available. In practice, general-purpose planters such as peanut seeders are often adapted for this crop. However, the dry seeds of C. esculentus exhibit an irregular shape, uneven surface texture, significant size variation, and poor flowability, leading to inadequate seed pickup and suboptimal seeding performance in conventional metering devices. To address these issues, two types of seed pickup devices—one with a V-shaped scoop and the other with an arc-shaped scoop—were designed to improve the seed-filling process and enhance seed agitation within the seed pool. A comparative analysis of the material properties of seeds before and after soaking was conducted, and key structural parameters of the scoops were determined based on the post-soaking characteristics. A mechanistic analysis was performed to clarify the operational principles and influencing factors of the scoop-based pickup mechanism. Using EDEM software (2022 version), the motion characteristics of seeds inside the metering device were observed, and the agitating speed of the seed population was compared with and without the scoop devices. Performance comparison experiments were carried out with two scoop types under varying conditions, including metering disc rotation speed, seed size grade (large, medium, and small), and seed moisture state (dry vs. soaked). Simulation results of seed disturbance indicated that the V-shaped scoop significantly enhanced agitation intensity, with a maximum movement velocity 15.8% higher than that of the arc-shaped scoop. The V-shaped scoop demonstrated superior stability and adaptability across different seed sizes, rotation speeds, and moisture conditions. Seed pickup success rates reached 96%, 96%, and 85% for large, medium, and small seeds, respectively. Under high-speed operation (40 r/min), the V-shaped scoop showed a 9% lower miss-seeding rate compared to the arc-shaped scoop.