To meet the operational criteria for mechanical transplanting of young seedlings in paddy-straw-made bowl-seedling trays, a new seedling needle and seedling pushing device have been developed. This paper presents the design process and analyzes the effects of key parameters, including the angle of inclination of flat edge, width of flat edge, length of flat edge, wedge angle, and width of seedling pushing device for new seedling needle and seedling pushing device. Optimization parameters of new seedling needle and seedling pushing device have been validated by orthogonal experiments. The optimized values, such as a flat edge inclination angle of 35°, a flat edge width of 10 mm, a flat edge length of 64 mm, a wedge angle of 60°, and a seedling-pushing device width of 8 mm, satisfy the operational requirements for mechanically transplanting young seedlings in paddy-straw-made bowl seedling trays. The results demonstrate significant improvements in transplanting efficiency within Chinese agricultural systems.

Addressing the issues of poor performance and low single-seed rate during seed filling and cleaning for corn, an air-suction roller precision dibbler was designed, and its main structure and working principle were elaborated. Based on the structure of the seed metering disk and the tri-axial dimensions of corn seeds, an auxiliary filling type hole boss was designed with a radius of 4 mm and a thickness of 1.5 mm. A sawtooth-type seed cleaning device was also designed, with an installation angle greater than 3° and a serrated chamfer less than 62.1°. By coupling the Discrete Element Method (EDEM) with Computational Fluid Dynamics (CFD), the flow field structure and seed metering performance were simulated and analyzed, examining the movement states of the seed population and individual seeds during the processes of filling, cleaning, carrying, and initial seed dropping. The variation patterns of the internal flow field pressure and fluid velocity of the seed metering device under different negative pressures and operating speeds were studied. Through the construction of a test bench and single-factor and three-factor orthogonal experiments, along with multi-objective optimization methods, the primary and secondary factors affecting the qualification index were determined. The optimization results showed that when the flow field negative pressure was 3.52 kPa, the operating speed was 5.81 km/h, and the suction hole diameter was 4.15 mm, the qualification index of the seed metering device was 93.2%, the missed seeding index was 3.3%, and the multiple seeding index was 3.5%. An adaptability test was conducted to verify these results, revealing that the qualification index for all three varieties of corn seeds exceeded 92.4%, the missed seeding index was less than 3.7%, and the multiple seeding index was less than 3.9%, satisfying the precision seeding requirements for corn seeds.

Machine transplanting, as an advanced production technology, is widely used for rice cultivation. However, the transplanted rice seedlings may float over and die under the stress of external force in extreme windy weather. In order to reveal the mechanism of floating rice seedlings, it is vital to investigate their force characteristics. In this study, steady-state simulations of the flow around the rice seedlings are conducted. It is found that the drag force of rice seedlings is generated by the positive pressure of the windward side and the negative pressure of the leeward side. Both the drag force and the moment are proportional to the square of wind speed, regardless of the wind direction angle or the inclined angle of rice seedlings. The drag force coefficient exhibits a complex pattern with the wind direction angle, but decreases as the inclined angle increases. The moment arm of the drag force initially increases and then decreases with increasing wind direction angles, while it decreases with larger inclined angles. It indicates that the variation in wind direction angle may increase the risk of lodging in rice seedlings, whereas the inclined angle does not have such an effect. The results of this study provide a valuable reference for preventing the floating of rice seedlings.