Design and experiment of seed tube of seedling planter for Panax notoginseng

Objective  In order to improve the accuracy of mechanized seeding of Panax notoginseng, according to the characteristics of small row spacing of P. notoginseng, a new type of seed guide tube was studied.

Method  The mechanical model was established with and without seed guide tube, respectively. The experiment was carried out in soil trough through the three-factor-five-level quadratic regression orthogonal rotation combination experiment with seed release height, seeder forward speed and seed release angle as the experimental factors, and the standard deviation of distance deviation between theoretical seeding point and actual seeding point, and bounce rate as the experimental indexes. With Design-Expert 10.0.3 software, the regression equation between test factors and indexes and the mathematical model of multi-objective optimization were established to get the best combination of seeding parameters. Under the optimal combination of parameters, high-speed camera technology was used to obtain the seed motion trajectory, and the curve equation of seed motion trajectory was studied by image processing technology and curve fitting method. With EDEM software, the cross-section size of seed guide tube was simulated and analyzed, and the cross-section size was determined. Seed guide tube was manufactured using 3D printing technology and seeding verification test was carried out.

Result  The common factors affecting seed motion with and without the seed guide tube were circumferential speed of seed merering device, seed release height and seed release angle. Through orthogonal rotation combination test, the optimal combination of seeding parameters was as follows: The seed release height was 20 cm, the seeder forward speed was 7.8 m/min and the seed release angle was 42°. Without seed guide tube, the standard deviation of distance deviation between theoretical seeding point and actual seeding point was 51.66 mm, and the bounce rate was 72.31%. The exit and entrance cross-section sizes of the developed seed guide tube were 26 mm × 30 mm and 26 mm × 60 mm, respectively. The verification test results showed that after installing the new seed guide tube, the standard deviation of distance deviation between theoretical seeding point and actual seeding point was 26.90 mm and the bounce rate was 45.20%.

Conclusion  The new seed guide tube satisfies the requirement of the mechanized seeding of P. notoginseng, the seeding accuracy after installing the new seed guide tube is obviously improved. The research results provide a reference basis for the design and field seeding application of the seed guide tube of P. notoginseng seedling seeder.