## 3 Precision Sowing Conditions of consistent Sowing-Depth Regulation
### Consistent Sowing-Depth Regulation Technology--Soil Compacting  
As the last and most critical part of precision seeding, the compacting wheel compacts the soil after soil covering, and aims to reduce evaporation to avoid frost damage and effectively promote the germination of seeds. The effect of compaction has a direct impact on the quality of sowing. As China is a vast country with significant environmental differences in different regions, the compaction requirements of crops are guaranteed to be met under the premise of meeting local agronomic needs. Soil-compacting devices developed in recent years form a full range of types, with many types of structural forms. The main component of the soil-compacting device is the soil-compacting roller; the current soil-compacting roller mainly exists in the form of cylindrical soil-compacting wheel [52],  
Figure 9: The proportion of soil cover in precision-seeding studies. concave or convex soil-compacting wheel [53], rubber soil-compacting wheel [54], and conical compound soil-compacting wheel [55] (Figure 10). Currently available soil-compacting devices vary in function and structural approach [56], and corresponding studies on the structural design of the soil-compacting wheel are being carried out. For example, [PERSON] designed a compact, three-way adjustable soil-covering and compacting device for the practical requirements of a no-till soil-covering precision-seeder soil-compacting device for wheat stubble fields. During the sowing operation, the soil covering the width and soil compacting intensity can be adjusted by the adjustment handle, according to the tillage environment and agronomic requirements [57]. [PERSON] designed a soil-compacting device with a function based on profiling function. The surface of the soil-compacting roller is designed with sticky reduction and an anti-slip structure, with the pressure seeding belt for pressure profiling adjustment. At the same time, this reduces the phenomenon of slipping of the soil-compacting wheel during the operation [58]. [PERSON] designed a flexible soil covering and compacting wheel, which can perform the profiling operation of the precision seeder and can realize the uniform distribution of soil-compacting pressure in different terrains [59]. However, in the actual operational process, the soil-compacting roller slippage of the soil-compacting device has become the primary problem to be solved by scientific researchers. Two main methods exist to solve the slippage problem: traditional and bionic viscosity reduction and resistance reduction. The following table compares the traditional viscosity reduction and drag reduction and the bionic viscosity reduction and resistance reduction methods (Table 3):  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
As the application of the bionic method in agricultural machinery becomes more widespread, more bionic soil-compacting devices with excellent performance are emerging, such as that designed by [PERSON] et al., which is a soil-compacting roller with a bionic convex package geometry, using the head of the dung beetle as a bionic prototype. This effectively realized the reduction in viscosity and resistance in the soil-compacting process by bionic biomorphic body shape, with the attendant advantages [60]. Faced with the problems of slippage and adhesion of the soil-compacting wheel and increased resistance caused by the actual field operation, [PERSON] et al. designed the bionic elastic soil-compacting roller by borrowing the flexible geometric features of the earthworm surface as the prototype. It has many advantages in viscosity reduction and resistance reduction, such as the uniform distribution of compacting pressure and a low slippage rate [61].