# Design and Test of Vertical Axis Rotating Cutters for Cutting Corn Roots and Crown
## 3 Results and Discussion
### Results of the Full-Factor Test
#### 3.2.2 Effect of Different Factors on the Rate of Soil Disturbance  
According to Table 3, the mathematical model relating the forward speed and rotational speed of the cutter shaft to the rate of soil disturbance was significant (\(p<0.01\)). The effect of both the forward speed and the rotational speed of the cutter shaft on the rate of soil disturbance was significant (\(p<0.01\)). And there were interactions between them (\(p<0.01\)).  
As shown in Figure 8, when the forward speed of the device was kept, the rate of soil disturbance increased with the increase in the rotational speed of the cutter shaft. The  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Source** & **Sum of Squares** & **df** & **Mean Square** & **F Value** & **\(p\)-Value Prob > F** \\ \hline Model & 0.17 & 24 & 7.229 \(\times\) 10\({}^{-3}\) & 4952.96 & \textless{}0.0001 \\ A & 0.100 & 4 & 0.025 & 17,068.60 & \textless{}0.0001 \\ B & 0.069 & 4 & 0.017 & 11,887.03 & \textless{}0.0001 \\ AB & 4.449 \(\times\) 10\({}^{-3}\) & 16 & 2.781 \(\times\) 10\({}^{-4}\) & 190.54 & \textless{}0.0001 \\ Pure Error & 7.297 \(\times\) 10\({}^{-5}\) & 50 & 1.459 \(\times\) 10\({}^{-6}\) & & \\ Cor Total & 0.17 & 74 & & & \\ \hline \hline \end{tabular}
\end{table}
Table 3: The mathematical model relating the forward speed and rotational speed of the cutter shaft to the rate of soil disturbance.  
Figure 7: Effect of different factors on the qualified rate of root-crown.  
reason was that as the rotational speed of the cutter shaft increased, the linear velocity of the tip of the cutters for cutting roots increased, thereby enhancing the kinetic energy of the blade. When the cutters penetrated the soil, the action of the cutters on the soil particles would cause higher kinetic energy, consequently leading to an increase in soil disturbance [37]. When the rotational speed of the cutter shaft was kept, the rate of soil disturbance was increased with the increase in the forward speed of the device. The reason was that the forward speed of the device increased, which resulted in a greater kinetic energy of the cutter. Therefore, the trend of soil moving forward was increased, and the soil disturbance was further aggravated [38]. Simulation data demonstrated that multi-curve cutters based on the distribution characteristics of roots in different soil layers and the corresponding mechanical properties of each soil layer could effectively reduce soil disturbance. This research not only provided a theoretical basis for structural optimization of the device for cutting the root-crown but also helped maintain soil structural stability by minimizing soil disturbance, thereby creating favorable conditions for subsequent soil moisture conservation in farmland. When the forward speed was 1.43 m\(\cdot\)s\({}^{-1}\) and the rotational speed of the cutter shaft was 540 r\(\cdot\)min\({}^{-1}\), the rate of soil disturbance was highest, and the value was 35.28%. When the forward speed was 0.71 m\(\cdot\)s\({}^{-1}\) and the rotational speed of the cutter shaft was 380 r\(\cdot\)min\({}^{-1}\), the rate of soil disturbance was lowest, and the value was 18.56%. According to the national standard, the rate of soil disturbance should not be exceeded by 30% [39]. Therefore, the operating range of the device that met the criteria was as follows: the forward speed of the device was less than 1.01 m\(\cdot\)s\({}^{-1}\) and the rotational speed of the cutter shaft was less than 460 r\(\cdot\)min\({}^{-1}\).