# Research Progress and Future Prospects of Key Technologies for Dryland Transplanters
## 3 Research Status of Seedling Picking Mechanism
### Discussion on the Current Situation of the Seedling Picking Mechanism  
The ejector-type seedling picking mechanism, with its straightforward operational principle, excels in transplanting scenarios requiring relatively low seedling integrity and uniform seedling pot specifications. For example, it efficientlyjects vegetable plug seedlings from trays. However, this mechanism is sensitive to pot material and hardness; overly rigid or deformed pots may cause extraction failure, and it struggles to adapt to seedlings with irregular shapes or sizes, limiting its applicability. Consequently, standalone research on ejector-type mechanisms has diminished, with most studies focusing on combined ejector-gripper systems. These mechanisms first loosen the seedling pot with an ejector and then extract and transport the seedling to the planting mechanism using a gripper.  
The gripper-type seedling picking mechanism encompasses various subtypes. The slideway-type achieves extraction through slideway-gripper coordination, featuring a relatively simple structure and easy maintenance. However, its single-mode slideway  
Figure 16: Schematics regarding the constructive and functional parameters of the automatic trans planter [128]. 1. planting driving wheel; 2. oscillating lever;3. control rod; 4. spur; 5. sliding rods; 6. planting device; 7. cam guide; 8. seedling; 9. fixed winged skids; 10. return springs; 11. ratchetsystem; 12. holding-release screen; 13. receiving tube of the distribution apparatus; 14. Seedlingstray.  
Figure 17: Seedling picking plan [134]. (**a**) Air-sweeping type. (**b**) Cylinder push-out type.  
motion compromises the balance between extraction accuracy and efficiency during high-speed operations, and adaptability to diverse seedling types remains to be improved. Non-circular-gear train seeding picking mechanisms leverage the unique kinematics of non-circular gears to execute complex gripping motions, enhancing extraction flexibility, efficiency, and stability. They suit crops with specific trajectory requirements for seedling extraction. Yet, their complex design, high manufacturing precision demands, and elevated costs restrict large-scale adoption. Mechatronic-controlled seeding picking integrates sensing and control technologies, enabling precise seedling position/posture perception for intelligent, accurate operations. Row-wise extraction boosts efficiency. However, reliance on complex control systems incurs high equipment costs and strict operator skill requirements, hindering popularization in economically underdeveloped regions or among small-scale farmers and rendering them unsuitable for field transplanting.  
The free-fall seedling picking mechanism utilizes gravity with appropriate auxiliary devices to drop plug seedlings directly into the planting position, causing minimal seedling damage but high medium fragmentation, and failing to preserve intact pots. This method imposes strict requirements on seedling morphology and falling path control, resulting in relatively low operational efficiency, along with high demands for mechanism installation precision and terrain evenness.  
Current research on seedling picking mechanisms faces significant challenges. On one hand, they must meet extraction demands for diverse crop varieties, planting patterns, and complex field conditions; on the other, they need to strike a better balance between enhancing extraction quality/efficiency and reducing equipment costs.