## 3 Results and Discussion
### Analysis of Field Tests Results
#### 3.2.2 Sidewall Compaction Force Control Effect  
The compaction was measured at 50 mm (set sowing depth) on the sidewall of the seed groove using a soil compactness meter and the average value was taken. The experimental study found that the mean value of post-sowing soil compaction with electro-hydraulic adjustment was 1100 kPa, which was about 15.8% higher than the mean value of the pre-sowing no-till soil compaction of 950 kPa. The soil compaction under the self-weight adjustment state fluctuated the most due to the vibration of the row unit during operation, caused by the undulation of the ground surface. The peak soil compaction at a depth of 50 mm below the ground surface was 1000 kPa during 5-6 km\(\cdot\)h\({}^{-1}\) operation, while the peak compaction reached 1500 kPa during fast operation. Compared with the mechanical spring adjustment, the soil compaction degree of the electro-hydraulic adjustment is less affected by the vehicle speed and is more stable. Combined with the analysis of the sowing depth data, it can be found that the shallow sowing depth point is always accompanied by low soil compaction, which shows that the downforce of the row unit is not enough to meet \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Number**} & **Target Compressive** & **Steady-State** & \multirow{2}{*}{**Peak/N**} & **Overshoot/\%** & **Steady-State** & **Adjustment** \\  & **Force/N** & **Value/N** & & & **Error/N** & **Time/s** \\ \hline
1 & 70 & 73.1 & 88.10 & 20.52 & 3.1 & 3.9 \\
2 & 140 & 144.25 & 164.83 & 14.26 & 4.25 & 5.2 \\
3 & 210 & 204.18 & 252.13 & 23.48 & 5.82 & 5.7 \\
4 & 280 & 272.83 & 299.28 & 9.69 & 7.17 & 6.1 \\ \cline{2-6} avg & & & & 16.99 & 8.63 & 5.23 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Sowing depth system dynamic test results. the working pressure required by the coupler, resulting in the gauge wheel being suspended on the surface without pressure, thus causing the sowing depth to be too shallow. This is also consistent with the growth relationship in Figure 15 where the sowing depth is positively related to the compaction. The total sowing depth measurement data of the front, middle and back sections were compiled and analyzed. The calculation results according to the index calculation method of Equations (17)-(20) are shown in Table 2. It can be seen that the error of the electro-hydraulic regulation in the average value of the sowing depth is the smallest, and the maximum error with the set value (50 mm) is only 0.73 mm, which appears at 9-10 km-h\({}^{-1}\). It can be seen from the qualified rate of the sowing depth that the self-weight regulation is influenced by the vehicle speed, while the mechanical regulation and electro-hydraulic regulation do not change much in value. The reason for the analysis is that the downforce provided when the row unit passes through some of the plots is overloaded, resulting in reaching the upper limit of the sowing depth while causing excessive soil compaction on the sidewalls of the seed groove. A further analysis of the standard deviation of the sowing depth showed that the standard deviation of the self-weight adjustment was 6.72 mm, which occurred at 7-8 km-h\({}^{-1}\). Combined with the analysis in Figure 15, this was due to the shallow sowing caused by the row unit's inability to provide sufficient downforce when encountering hard plots, while the mechanical and electro-hydraulic adjustments reduced the coefficient of variation of the sowing depth by virtue of sufficient downforce and improved the sowing depth qualification rate. Figure 15: Sowing depth and compaction data of three adjustment methods at different vehicle speeds: (**a-c**) self-weight adjustment; (**d–f**) mechanical adjustment; (**g–i**) electro-hydraulic adjustment. In this section, the data of [PERSON]'s study [31] show that the sowing depth qualification rates under electro-hydraulic control conditions are 88%, 82% and 78%.