# Research Progress and Future Prospects of Key Technologies for Dryland Transplanters
## 2 Classification of Transplanters
### Semi-Automatic Transplanter
#### 2.2.1 Duckbilled Semi-Automatic Transplanter  
During operation of the duckbill transplanter, the operator places plug seedlings into the duckbill planting mechanism. Once the planting mechanism penetrates the soil, the \"ducbill\" opens under cam control, allowing the plug seedlings to be planted. Transplanting is completed by the combined action of soil backfill and the soil covering mechanism. This type of transplanter enhances overall work efficiency by incorporating multiple planting units. However, due to manual seedling feeding, operators must promptly adjust the feeding speed to match increases in planting speed. Prolonged high-intensity manual labor often leads to an increase in seedling miss rate, significantly affecting transplanting performance [55]. Figure 3 illustrates the classification and working components of the duckbilled semi-automatic transplanter. [PERSON] et al. [56] designed a two-row semi-automatic vegetable transplanter suitable for small-field transplanting, as shown in Figure 4a. During operation, the machine is towed by a tractor, and operators standing on the transplanter remove seedlings from trays and place them into a hollow pipe. As the rotating disc turns, seedlings are released at the seedling dropping point and dropped into the planting mechanism to complete transplantation. [PERSON] et al. [57] developed a multifunctional semi-automatic vegetable transplanter (Figure 4b), which uses tractor traction for power and employs a linkage-ducbill planting mechanism. It can synchronously perform processes including drip irrigation tape laying, mulching, fertilization, transplanting, soil covering, and watering. Figure 2: Handheld Transplanter. (**a**) Structure diagram of the handheld transplanter: 1. Seeding feeding port; 2. Handle 1; 3. Handle 2; 4. Seeding guide tube; 5.Upper pull cable; 6. Lower pull cable; 7. Pedal; 8. Jaw-type planting device. (**b**) Planting process of the handheld transplanter: 1  
The duckbill-type seedling planting mechanism employs driving mechanisms such as linkage and planetary gear train types [19]. The linkage planting mechanism is widely used due to its low cost and ability to achieve diverse operating trajectories. Research on linkage planting mechanisms primarily focuses on mechanism configuration, which has evolved from the simplest four-bar linkage to seven-bar linkages and gear-linkage composite mechanisms. Although the linkage planting mechanism can meet the specific trajectory and posture requirements for vegetable transplanting, it has inherent characteristics such as high inertia and significant vibration, which hinder its adaptation to high-speed transplanting [37]. To further improve transplanting efficiency, scholars have proposed a planetary gear train planting mechanism [58; 59], mainly composed of a planetary gear train and duckbill-type planter, as shown in Figure 5. During operation, the planting mechanism advances with the transplanter, and when driven by the planetary gear train, the duckbill-type planter traces a specific planting trajectory. A cam on the planter controls the opening and closing of the duckbill, enabling mechanized planting. A comparison of duckbill-type planting mechanisms is presented in Table 2.  
Figure 4: Duckbilled semi-automatic transplanter. (**a**) Two-row semi-automatic vegetable transplanter [56]. (**b**) Multifunctional vegetable semi-automatic transplanter [57].