Analysis and experiment of the root stability of breeding potato single plant harvesting

Aimed to solve the problems of low efficiency of manual harvesting and easy rupture of mechanically when harvesting potato aggregates in potato breeding experiment, 4U-80DZ potato harvester was selected as the analysis basis, and took asexual-generation potato in the secondary cropping area of Central China as the research object. The excavation shovel entry angle-plant root system model was established in the process of excavation by mechanical and kinematic analysis of potato root aggregates. It was concluded that the horizontal acceleration of potato root system was -1.47～5.325 m/s², which increased with the increase of the excavation shovel entry angle, and the vertical acceleration was -0.19～8.127 m/s², which decreased with the increase of the excavation shovel entry angle, and the potato root system was transversely broken, and the single plant stability decreased. A potato root vibration model was established during the conveying process. Through analyzing the velocity and force of potato root system, it was concluded that the displacement of potato tuber affected the integrity of single plant, the displacement of potato tuber along the conveying direction was a function of time, which first decreased and then increased with the increase of conveying time, the displacement of potato tuber in the direction of vibration is also a function of time, which increases first and then decreases with the increase of transport time, and presents the reciprocating motion in the direction of vibration and the conveying direction. A potato tuber-root-soil model was constructed by using discrete element simulation method. The integrity rate of single plant was represented by tuber-stolon force, stem-stolon force and tuber-stolon displacement, and the degree of root breakage was simulated when the digging and shovel entry angle was 20°～30°. The force curves of potato tuber - stolon, stem - stolon and the displacement curves of tuber relative to stolon were obtained at 20°, 25° and 30°, and the optimum the excavation shovel entry angle was determined to be 20°～28°. A three-factor quadratic orthogonal rotation combination experiment was designed with the excavation shovel entry angle, the forward speed and the vibration frequency of conveying device as test factors, and integrity rate of potato single plant as experiment index. Response surface analysis and parameter optimization were carried out, the results showed that the significant factors affecting the integrity rate of single plant were that the forward speed was greater than the excavation shovel entry angle, and the excavation shovel entry angle was greater than the vibration frequency. The best combination of parameters with the maximum degree of root system integrity was as follows: the excavation shovel entry angle was 21.8°, tool forward speed was 0.96 km/h, vibration frequency was 1.44 Hz, and the integrity rate of single plant was 100%. Field experiment results under this parameter combination showed that the average integrity rate of single plant is 95.1%. This study provided the basis for the selection of parameters of potato harvester for breeding experiment, and laid the theoretical foundation for the design of potato harvester for breeding experiment.