# Research Progress and Future Prospects of Key Technologies for Dryland Transplanters
## 1 Introduction  
Transplanting is the process of transferring seedlings grown in biochar or other substrates from seedling trays to the field through technical means [1, 2, 3, 4, 5], including manual and mechanized transplanting. Transplanting technology can significantly improve the cropping index and prolong the utilization cycle of light and heat resources by shorteningthe field growth period and avoiding low temperature stress during the seedling stage, providing key technical support for crop yield and efficiency increase [6; 7; 8; 9; 10; 11; 12; 13], and facilitating biomass allocation [14]. Among numerous crop varieties, most are suitable for transplanting operations, including rice, cotton, corn, vegetables, and rapeseed [15; 16; 17; 18]. Since the 1920s, scholars have been researching transplanters, whose development exhibits typical regional characteristics [19]. For instance, European and American countries typically adopt mechatronic-hydraulic integrated technologies to develop transplanters, featuring intelligence, large-scale operation, high efficiency, and strong universality; while Japan, South Korea, and other nations prioritize compact and miniaturized transplanters. Korean scholars [PERSON] et al. [20] conducted a kinematic analysis on various transplanters and their main components, detailing the working principles, field efficiency, and transplanting accuracy of different vegetable transplanters. Turkish scholar [PERSON] et al. [21] evaluated the transplanting performance of transplanters for tomato and watermelon plug seedlings under field conditions, finding that the angle between seedlings and the vertical plane was less than 30\({}^{\circ}\) after operation by all transplanters. Only disc-type transplanters caused seedling damage exceeding 3%, while all transplanters achieved a seedling survival rate above 90%. Bangladesh scholars [PERSON] et al. [22] designed, manufactured, and tested two semi-automatic vegetable transplanters--dibbler vegetable seedling transplanter and the furrow opener vegetable seedling transplanter--assessing their performance and impact on field crop productivity. Romanian scholars [PERSON] et al. [23] conducted a comparative study on common transplanters and proposed optimal solutions based on agricultural technical requirements for seedling transplantation. China, though late-starting in transplanting machinery research, has developed diverse transplanters for different crops, including semi-automatic and fully automatic models. Some fully automatic transplanters integrate advanced auxiliary technologies, such as Beidou-based automatic navigation systems, sensors, and vision-based monitoring systems [24; 25; 26; 27; 28; 29; 30; 31; 32]. The fully automatic transplanting machine comprises multiple operating components, such as planting mechanisms, seedling picking mechanisms, seedling supply mechanisms, and auxiliary devices [33], with the seedling picking mechanism serving as its core component. Research on seedling picking mechanisms has been extensive. Korean scholars [PERSON] et al. [34] developed a top-ejecting onion seedling picking mechanism to meet the mechanized transplanting requirements of onions. Based on variations in needle diameter and operational speed, the study analyzed seedling pull-out resistance and damage rate, indicating that pull-out resistance increased with the increase in the push rod diameter. [PERSON] et al. [35] designed a single-degree-of-freedom seedling picking and dropping robotic arm, driven by a four-bar mechanism and sliding mechanism to achieve precise seedling picking trajectories and postures. Experiments showed that the seedling picking success rate reached 96.7%, the seedling plug damage rate was 3.13%, the seedling dropping success rate was 97.74%, and the transplanting success rate was 91.32%, demonstrating high mechanism reliability. [PERSON] et al. [36] devised a planetary non-circular gear mechanism enabling dual unequal transmission ratios.