# Current Status and Future Directions for Combined Tillage and Sowing Technology and Equipment
## 4 Research on Precision Sowing Technology
### Mechanical Precision Seed Metering Device
[PERSON] has designed an inclined disk seed metering device (Figure 11), in which the seed filling operation relies on the need for the weight of the seed, the seed in the holes rotates with the disk into the furrow, and the device is simple in structure, meaning it is not easy to injure the seed, and the design is adapted to round seeds [81]. [PERSON] et al. designed a tilted disk seed metering device with a simple structure, which has a good seed filling effect and is adaptable to the requirements  
Figure 10: Schematic of hook–hole-type seed metering device. of high-speed operation, studied the filling and clearing work of the device and the main structural parameters, and optimized the number of holes and hole type, the inclination angle, and so on [82]. [PERSON] optimizes the existing disk seed metering device based on the shape and size of many types of seeds, designing the key parameters and structure, and expanding the adaptive scenarios of the machine [83]. [PERSON] designed a tilt disk-type fine-and-small-amount-of-seed metering device for small grain seeds. Through the design of the seeding device, it achieved stable displacement and even seeding [84]. In order to improve the seed filling capacity and reduce the leakage rate and seed injury rate, [PERSON] designed a horizontal disk seed metering device for Cyperus esculentus with a conical structure design and crop clearing brushes made of rubber rods, which reduces the damage of the operation to the seeds [85]. The disk seed metering device is widely applied in small and medium-sized machinery. Most of the related research mainly focuses on improving its adaptability to different crop seeds, its seed-filling performance, and the sowing quality under high-speed operations. The performance of the equipment is enhanced by means of structural innovation, parameter optimization, material replacement, and so on. The disk-type precision seed metering device has good adaptability to round seeds, but its operation effect on flat seeds is not good, and it is easy to leak seeds. The finger-clamp-type seed metering device clamps the seed through the spring, which has good adaptability to corn and other flat-shaped seeds, stable operational performance, and effectively solves the problem of seed leakage. Precision Planting and Kinze have optimized the picker finger seed metering device. A cushion was added to the seed guide housing to reduce rebound collisions, and the seed cleaning brushes, bumpers, and seed guide belt blades were optimized to improve the seeding rate and straightness, and the seed metering device is shown in Figure 12[86]. [PERSON] designed a ripple surface pickup finger maize precision seed metering device by adopting the methods of clamping seed filling, vibrating seed clearing, transporting seed guiding, and smooth seed casting. The design creates a corrugated curved finger clamp that can effectively clamp and fill the seed, explores the mechanism of precise seed discharge operation, and provides a new idea for the design of a picker finger seeder [87]. Combined with the agronomic requirements of corn planting, [PERSON] designed a swinging finger clip corn seed metering device. It improves the structure of the working parts, optimizes seeding performance, improves reliability, and solves the problems of the complicated structure and high working resistance of the current picker finger seed metering device [88]. Due to the structural characteristics and working principle of the picker finger seed metering device, it is currently used more in the sowing of maize crops, and less in the use of small grain crops. [PERSON] et al. developed a clamping potato precision seed metering device, performing the seeding operation through the opening and closing of the seed clamp plate and swing, where the reseeding rate and leakage rate are low, to meet the operational requirements [89].