Sweet potato is widely cultivated in China, which is the largest sweet potatoes producing countries in the world. However, because of the complex agricultural requirements for sweet potato cultivation, traditional manual planting is time-consuming and laborious, and the planting quality is difficult to meet the requirements. These reasons have resulted in a mechanization level of only 26% for sweet potato cultivation in China. At present, the commonly used agronomic requirements for sweet potato planting are raised beds with mulching planting. Under the mulched ridge planting mode, the working mechanisms of the two clamp-type transplanting devices (end-face cam transplanting device and disc cam transplanting device) are currently more suitable for the agronomic requirements of this planting mode are unclear, resulting in poor stability of sweet potato planting quality. In order to clarify the mechanism of how transplanting equipment affects seedling planting posture, this study comparatively analyzed two clamp-type devices—end-face cam and disc cam configurations—using integrated ADAMS-EDEM coupling simulations and field validation. A multi-physics model was developed, incorporating seedling flexible deformation, soil viscoelastic response, and device motion trajectory to determine optimal operational parameters. Systematic investigations revealed dynamic responses during transplanting, including soil insertion length, planting depth, and soil disturbance patterns. The simulation results show that the length of potato seedlings in soil by the end-face cam-type and disc cam-type transplanting devices is both 150 mm, with planting depths of 83 mm and 104 mm, respectively. The soil disturbance rates are 11.86% and 21.54%, and the theoretical film-breaking opening area are 6244.4 mm² and 2519.2 mm². The results indicate that the end-face cam-type transplanting device causes less soil disturbance, while the disc cam-type device demonstrates superior control over film-breaking opening sizes, which fully met the needs of field operation. Furthermore, the field experiment was carried out in the field under optimized parameters including a working speed of 120 mm/s, main rocker arm rotational speed of 30 r/min. The field experiment result showed that the length of potato seedlings in soil of the end-face cam-type and disc cam-type transplanting devices were 164 mm and 168 mm, with qualified rates of planting length in soil reaching 95.0% and 94.5%, respectively. The average depth of potato seedlings in soil were 91 mm and 98 mm, with qualified rates of planting depth in soil being 93.7% and 95.2%, respectively. The average film-breaking opening area were 5640 mm² and 2320 mm², with qualified rates of film-breaking opening area exceeding 97.0% for both transplanting devices. The corresponding relative errors between the ADAMS–EDEM coupling simulation values and the field trials were as follows: 8.53% and 10.71% for the average length of potato seedlings in soil, 8.79% and 6.12% for the average depth of potato seedlings in soil, and 10.72% and 8.58% for the average film-breaking opening area. All these errors fall within an acceptable range, thereby demonstrating the accuracy of the model. Based on the above theoretical analysis and field experiment results of the transplanting devices, this study proposes differentiated optimization measures for the two types of transplanting devices. For the end-face cam-type transplanting device, increasing the roughness of the seedling clamp contact surface can reduce the displacement of sweet potato seedlings in the seedling clamp. The disc cam-type transplanting device requires optimization of the cam profile to reduce abrupt changes in the profile, thereby minimizing soil disturbance. Additionally, both transplanting devices are equipped with synchronous compaction mechanisms to eliminate soil cavities. This finding is of considerable importance to developing the transplanting machine for planting sweet potato seedlings on mulched ridge planting systems, as well as for sustainable development of the sweet potato industry.

Sweet potato is one of the most favorite crops that is widely cultivated from the tropical to temperate regions. There is an ever-increasing need to produce more sweet potatoes on the existing arable land under the challenges of labor scarcity and population growth. However, it is still lacking the optimal machinery to transplant the spring sweet potato seedlings on mulched ridge planting system, especially in the hilly and mountainous region of northern China. In this study, a profiling transplanter was designed for the "shallow planting and multiple buried joints" of sweet potato seedlings, according to the agronomic requirements of "shallow cultivation and multiple burying nodes". The boat-bottom planting placement of mulch raised the beds' cultivation system of sweet potatoes. The space-time coordination and working parameters of the transplanting unit were optimized to consider the transplanting angle, transplanting depth, seedling length under the film and hole length. Indoor and outdoor tests were also carried out to verify the model. The indoor seedling-taking tests showed that the planting unit posed the super seedling taking effect on the five sweet potato varieties, which were widely planted in Huang-Huai-Hai area. More narrowly, the seedling picking success rates of the planting unit were more than 99% under the rotating speeds of 40-50 r/min, which fully met the needs of field operation. Furthermore, the orthogonal experiment of field transplanting was carried out in the field, in which the influencing factors were taken as the operation speed, the shape of sweet potato seedlings base, the length of seedlings extending out of the brush, and the average number of buried nodes, the qualified rate of transplanting depth, and the missing rate determined as the evaluation indexes. The field experiment showed that the influence factor on the average number of buried nodes was ranked in the descending order of the length of seedlings extending out of the brush, the operation speed, and the shape of the sweet potato seedlings base. By contrast, the influence factor on the qualified rate of transplanting depth was the length of seedlings extending out of the brush, the shape of the sweet potato seedlings base, and the operation speed. The influencing factors on the missing seedling rate were the operation speed, the shape of sweet potato seedlings base, and the length of seedlings extending out of the brush. The operating parameters were optimized using fuzzy evaluation and range analysis. As such, each factor on the comprehensive score of field experiment performances was ranked in the descending order of the length of seedlings extending out of the brush, the shape of the sweet potato seedlings base, and operation speed. The optimal combination of parameters was as follows: the operation speed of 0.5 km/h, the most upright sweet potato seedlings base, and the extension length of sweet potato seedlings of 60 mm. Finally, the transplanting efficacy of the sweet potato seedlings profiling transplanter was evaluated under the optimal operation parameters in the hilly and mountainous regions. The results showed that the average transplanting depth, the transplanted seedling length under the film, the hole length, and the transplanting angle were 73.6, 205.4, 76.5 mm and 53.8°, respectively. Meanwhile, the transplanting space variation coefficient, the qualified rate of planting depth, and the rate of missing seedlings were 8.9%, 93.7%, and 3.5%, respectively. The performance fully met the agronomic requirements of "shallow cultivation and multiple burying nodes" for the boat-bottom planting placement and the regulations of transplanting quality on dry land transplanting equipment. This finding is of considerable importance to developing the transplanting machine for planting spring sweet potato seedlings on mulched ridge planting systems in the hilly and mountainous regions of northern China, as well as for sustainable development of the sweet potato industry.