Sowing quality is directly influenced by the seed-filling characteristics of a centralized seed-metering device, and vigorous seed-motion status deteriorates seeding performance resulting from field surface roughness, seeder vibration, etc. However, the relationship between vibration and seed-filling properties remains unclear. This study measured the vibration characteristics of a seed-metering device, examined unmeasurable seed-motion characteristics based on DEM simulation, and used bench tests to determine the seed-filling characteristics under vibration conditions. The frequency distribution of the rapeseed seeder was 0–180 Hz. The simulation results revealed that the vibration mainly changed the level of seed in the seed-filling area; moreover, it significantly increased the seed-filling angle, ranging from 56.00°–59.00° to 69.78°–91.40°, which affected the seed-filling performance. A vibration frequency of 10–40 Hz resulted in a target seed rate within 88.67–99.44%, but when there is no vibration, the target seed rate reached 100%. The bench test results demonstrated that the seed-filling angle under vibration will increase with an increase in longitudinal distance, and will change between 15.49°–102°. The seed-filling performance affected by longitudinal distance was larger than that affected by lateral distance. By adjusting the longitudinal distance to range from 0–20 mm, the target seed rate could be maintained above 91%. The findings help to improve our knowledge of seed-filling characteristics under vibration conditions, and should be conducive to improving seeding performance by adjusting the seed layer height to reduce the impact of vibration on field operations.

Rapeseed is mainly cultivated in hilly areas in China and the inclination angle is an important parameter for influencing the seeding quality of a seed-metering device. However, the relationship between seeding performance and inclination angle remains unclear. This study analyzes the influence of inclination angle (θ) on the characteristics of seed-filling and seeding performance in a centralized seed-metering system of rapeseed using DEM simulation and the bench test. The results revealed that the inclination angle (θ) had a significant effect on seed-filling performance. The missing seeds ratio and the deviation of seed layer height increased with an increase in a lateral inclination angle. The missing seeds ratio in the forward direction (−Y direction) and seed-filling angle, double seed-filling ratio, and seed layer height in the back direction (Y direction) increased with the increasing inclination angle. Under seed-cleaning treatment, the missing seeds ratio was significantly reduced in the −Y direction at a seed layer height of 25 mm, and the qualified ratio was more than 91.0% at a seed layer height of 20 mm in X direction. The phenomenon of seeds passing through the seed-metering wheel disappeared with a qualified ratio larger than 90.0% in Y direction by installing a seed-cleaning brush. The results contributed to improving the knowledge of seed-filling characteristics of the centralized seed-metering device at inclination conditions and should help to improve seeding performance by adjusting the seed layer height and installing a seed-cleaning brush.

Conventional nitrogen fertilizers are often constrained by a short effective period, high nitrogen loss rates, and low nitrogen use efficiency (NUE). Novel amino acid-based fertilizers, such as polyaspartic acid (PASP)-urea, offer a promising solution to mitigate nitrogen losses and enhance crop NUE. To evaluate the efficacy of PASP-urea in paddy fields, field and pot experiments were conducted in 2019 and 2020 using two rice cultivars, Shuhui 498 and Duohui 1. The study assessed three fertilizer treatments: PASP-urea, conventional urea, and a no-urea control. By analyzing soil and plant nitrogen content, root architecture, gene expression, and grain yield, this study investigated the relationship between PASP-urea application, soil nitrate distribution, and root architecture configuration. Compared with conventional urea, PASP-urea significantly increased nitrate concentration in the 0–10 cm soil layer for both rice varieties by 45.8–81.4% at 30 days after tillering fertilization. Concurrently, it significantly upregulated the expression of nitrate transporters NRT1.1A and NRT1.1B and promoted greater root distribution in the nitrate-enriched topsoil. This root distribution pattern promotes the uptake and utilization of nitrogen by rice plants. Consequently, PASP-urea increased grain yield by 6.7–11.7%, while nitrogen agronomic efficiency (NAE), nitrogen recovery efficiency (NRE), and nitrogen partial factor productivity (PFP) increased by 15.2–25%, 17.8–49.6%, and 6.8–11.2%, respectively. These results indicate that PASP-urea enhances NUE and is associated with increased topsoil nitrate concentration, upregulated nitrate uptake genes, and a remodeled root architecture, offering a viable strategy for sustainable rice production.