## 3 Precision Sowing Conditions of consistent Sowing-Depth Regulation
### Consistent Sowing-Depth Regulation Technology--Soil Covering  
The purpose of the soil covering device is to protect the seed that falls into the seed bed, creating an environment for seed germination and growth that directly impacts seed spacing and seedling emergence. According to the current test results, the structural and operating parameters of soil-covering devices directly influence the performance of soil covering. High soil-covering quality is required to ensure consistent thickness and uniform soil-covering volume during precision seeding operations [42]. The ordinary soil-covering device has three classifications: disc, extruded, and plate type soil-covering device (Figure 8). [PERSON] designed the disc soil-covering device consisting of two discs arranged at a specific angle. Its structure is adjustable, so the amount of soil covering can be adjusted by changing the device's opening and tilt angles. The spacing between the double discs can be changed according to different operating conditions to meet the actual operating requirements of varying seed furrows [43]. In addition, the device has the advantages of low resistance and stable operation in the process of operation. Figure 8: Soil-covering device. (**a**) Disc soil-covering device. (**b**) Extruded soil-covering device. (**c**) Plate-type soil-covering device. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Type** & **Advantage** & **Disadvantages** \\ \hline Mechanical type & Simple structure and low cost & Poor adaptability, inconvenient adjustment, and inability to regulate town pressure in real time \\ Pneumatic type & No over-compaction and & Slow response time \\  & town-pressure regulation & \\ Hydraulic type & Faster speed adjustment of town pressure & \\  & is possible & More complex structure than mechanical type \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Sowing monomer adjustment method. The extruded soil-covering device's main structure comprises two opposing angled wheels, which can be adjusted by a tie rod before an operation to change the soil compacting and covering effect. The main factors affecting the operating outcome are the operating speed and the size of the wheel-body clamp angle [44]. The plate-type soil-covering device can be used in a corn seeder; part of the device can be adjusted, according to the shape of the open furrow and the size of the required mulch thickness, and with the characteristics of simple structure, the factors affecting the soil-covering effect are soil-covering inclination and the opening angle [45]. As the part is in contact with the soil of the seed bed arrangement, the soil-covering-device operation can provide the material conditions such as moisture, temperature, and the nutrients required for seed germination, which profoundly impacts the yield and quality of crops. Its soil covering technology and the performance of its equipment directly affect the quality of seeding and operational efficiency. Scholars and experts in China and abroad have researched the problems of the soil cover's poor mass and stability problems. For example, [PERSON] et al. modeled the cutting soil dynamics of the disc soil-covering device and analyzed the relationship between cutting stress and cutting angle and shear rupture angle, during the operation of the disc soil-covering device and based on the SPH meshless method. The simulation of the optimal parameter ratio effectively analyzed the displacement of the seeds after touching the soil, with the change in soil flow movement during the operation of the disc soil-covering device [46]. [PERSON] et al. used a uniform design method to design a double-layer disc-type soil-covering device to reduce the displacement of seeds during soil covering, and conducted tests and evaluations on the prepared soil-covering device [47]. [PERSON] et al.