Low light stress increases the chalkiness of rice; however, this effect has not been fully characterized. In this study, we demonstrated that low light resulted in markedly decreased activity of ADP-glucose pyrophosphorylase in the grains and those of sucrose synthase and soluble starch synthase in the early period of grain filling. Furthermore, low light also resulted in decreased activities of granule-bound starch synthase and starch branching enzyme in the late period of grain filling. Therefore, the maximum and mean grain filling rates were reduced but the time to reach the maximum grain filling rates and effective grain filling period were increased by low light. Thus, it significantly decreased the grain weight at the maximum grain filling rate and grain weight and retarded the endosperm growth and development, leading to a loose arrangement of the amyloplasts and an increase in the chalkiness of the rice grains. Compared to the grains at the top panicle part, low light led to a greater decrease in the grain weight at the maximum grain filling rate and time to reach the grain weight at the maximum grain filling rate at the bottom panicle part, which contributed to an increase in chalkiness by increasing the rates of different chalky types at the bottom panicle part. In conclusion, low light disturbed starch synthesis in grains, thereby impeding the grain filling progress and increasing chalkiness, particularly for grains at the bottom panicle part.

The discrete element method (DEM) is an effective tool for obtaining qualitative and quantitative information on particle motion, which aids in the design and optimization of agricultural equipment structures. The accuracy of the DEM simulation parameters significantly impacts the simulation results. This study employed a combination of high-speed camera measurement, DEM simulation, and validation tests to determine the material and interaction property parameters for fertilizer particles. The basic parameters (triaxial size, bulk density, density, and coefficient of static friction) and coefficients of restitution between fertilizer and material were measured for three fertilizer varieties. There was a significant difference in the angle of repose between various material plates and fertilizer particles. The calibration values of coefficients of restitution and coefficients of rolling friction between fertilizer particles were optimized using the Box–Behnken method. The angle of repose was significantly affected by the coefficient of static friction and the coefficient of rolling friction between the fertilizer particles. The determined values for the coefficient of restitution, coefficient of static friction, and coefficient of rolling friction between the fertilizer particles were 0.323, 0.381, and 0.173, respectively. The error in the angle of the repose test was less than 3.0%, and the variation coefficient for each row consistency was less than 1.68 percentage points under the optimal simulation parameters. DEM simulations of the angle of repose and each row consistency variation coefficient test using the measured parameters can accurately predict the experimental results. The findings of this paper provide a theoretical basis for the DEM study of fertilizer particles.

In order to analyze seed movement characteristics and improve seeding quality of air-assisted centralized metering device for rapeseed, the effects of the model-hole structure on seed feeding performance were investigated using EDEM simulation. Furthermore, the CFD-DEM coupling approach was applied to determine movement trajectories and airflow fields. The impacts of rapeseed varieties and rotational speed on seeding performance were investigated by bench tests. The results showed that the seed feeding quantity increased with the increase of model-hole’s length, depth and section size. Under the model-hole’s depth of 3.0 mm, the type Ⅱ model-hole and model-hole’s length of 10 mm, both the variation coefficient of seed feeding quantity and hill diameter were lower which meet the seeding quantity requirement of 2 seeds in each hill. It was revealed that the seed population migrated in a large airflow velocity area and the distribution was uniform. The bench tests indicated that rapeseed varieties and rotational speed had a significant effect on the seed feeding quantity in each hill at rotational speed of 10-40 r/min. The variation coefficient of seed feeding quantity in each hill was less than 17.0% for each treatment. The hill diameter, which did not exceed 3.5 cm, tended to reduce with increasing rotational speed. The variation coefficient of seeding quantity in each row and seeding uniformity was less than 6.5% and 32.0%, respectively. Field experiments demonstrated that the seedling was 9-13 plants per meter each row for three rapeseed varieties. The variation coefficient of plants was less than 25.0% for six rows and their yields reached 2761 kg/hm2, which realized the mechanized planting requirements. The results can optimize structure of an air-assisted centralized metering system and improve in seeding performance. Keywords: rapeseed, air-assisted centralized metering device, seed hill feeding, seeding performance DOI: 10.25165/j.ijabe.20211405.5349 Citation: Lei X L, Hu H J, Yang W H, Liu L Y, Liao Q X, Ren W J. Seeding performance of air-assisted centralized seed-metering device for rapeseed. Int J Agric & Biol Eng, 2021; 14(5): 79–87.

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.

To address the problems of missed and false detections caused by insufficient feature quality in small object detection from UAV perspectives, this paper proposes a UAV small object detection algorithm based on YOLOv8 feature optimization. A spatial cosine convolution module is introduced into the backbone network to optimize spatial features, thereby alleviating the problem of small object feature loss and improving the detection accuracy and speed of the model. An improved C2f_SCConv feature fusion module is employed for feature integration, which effectively reduces feature redundancy in spatial and channel dimensions, thereby lowering model complexity and computational cost. Meanwhile, the WIoU loss function is used to replace the original CIoU loss function, reducing the interference of geometric factors in anchor box regression, enabling the model to focus more on low-quality anchor boxes, and enhancing its small object detection capability. Ablation and comparative experiments on the VisDrone dataset validate the effectiveness of the proposed algorithm for small object detection from UAV perspectives, while generalization experiments on the DOTA and SSDD datasets demonstrate that the algorithm possesses strong generalization performance.

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.