## 2 Precision Seeding Technology
### Consistent Sowing-Depth Regulation Technology  
Precise seed discharge technology, smooth seed-guiding technology, and the seed falling into the seed bed with precision in the above Precision seeding operation, aim to achieve grain-spacing consistency by regulating the seed migration process [39]. Sowing depth is an essential factor affecting the emergence of crops; in line with the crop, agronomy sowing depth conditions the healthy sprouting, growth and development of harvests; if the sowing depth is too shallow, it is not conducive to the seeds fully absorbing the soil nutrients, the root system is not fully developed, leading to the seedling being weak and prone and a lack of seedlings, with other situations which easily cause yield a reduction in the yield; if sown too deep, it is not easy for the seed sprout to break through the soil surface layer, resulting in the late emergence of weak seedlings, uneven emergence, and other situations [40]. During the precision seeder operation, the device's vibration is caused by the change in soil resistance of the devices in contact with the soil, resulting in a difference in the sowing depth. Therefore, the research into soil covering and compacting under the agronomic requirements to ensure the consistency of sowing depth provides the theoretical basis for designing and modifying the devices in contact with the soil precision seeder and then realizing the purpose of improving the quality of the sowing operation and increasing the profit. It is essential to enrich and enhance the soil covering and compacting technology, improve the reliability of the devices in contact with the soil of the seeding machine, and realize the sowing effect of a consistent sowing depth. Foreign agricultural equipment companies, such as John Deere, developed precision seeders mainly by installing terrain-adapting wheels on both sides of the furrow opener to regulate the depth of the furrow according  
Figure 6: Precision seeder seed-pressing device. Figure 7: Plastic seed-pressing tongue. to the terrain, to achieve the purpose of a consistent sowing depth. At the same time, some other foreign companies have detected the depth of furrowing through the sensor installed in the seeding unit. Suppose the depth of furrowing does not meet the operation requirements. In that case, the hydraulic system will regulate the planting monomers to achieve real-time regulation of the furrowing depth to achieve consistent sowing depth. The foreign precision seeder achieves consistent sowing depth, mainly through the four-bar construction, combined with the terrain-adapting wheel and sensor-assisted monitoring, ensuring that the accuracy of terrain adaptation can be applied to high-speed operation in large fields. Nevertheless, the foreign precision seeding operational mode, environment, and domestic differences, which make this alien technology for sowing depth control, can only partially apply to the sowing depth control in China. Relevant research has been carried out in China for sowing depth consistency; for example, [PERSON] designed a sowing depth control mechanism for a corn no-till seeder using microcontroller control, wireless communication, and other technologies to ensure high consistency of sowing depth in the corn seeder, which effectively improved the quality of the sowing operation [8]. [PERSON] designed a sowing depth control device for potato precision seeders in hilly mountainous areas, effectively enhancing the potato sowing depth uniformly; the device operation had good stability [41]. From the above analysis, the research on precision seeding at home and abroad is divided into four areas. The first one is the precision seed discharge, and the current research on the seed metering device; the pneumatic seed metering device has a better operational performance than the mechanical seed metering device, which is more suitable for research into the precision seed metering device.