Research progress in mechanized lifting technology of apple seedlings

Abstract: The cultivation of apple trees in China has gradually shifted from the traditional mode of tall trees to the intensive dwarf and high-density planting mode. The cultivation of apple seedlings has grad-ually become standardized on a large- scale. The nursery of seedlings is the last step of the nursery work. A good nursery technology can shorten the post-planting slow-seedling period, enhance the resis-tance of seedlings, and increase the survival rate of seedlings. As the key equipment for the nursery stocks, the seedling lifter plays an important role in the process of seedling cultivation. The seedling lift-er is a machine that separates the seedlings from the growing soil in the nursery through the tractor. The seedling lifter can be divided into four types: ridge type, bed type, comprehensive type and large seed-ling type. The application of the seedling lifter avoids the disadvantages of manual lifting of seedlings,such as high intensity, repeated operations, and easy damage to the roots of the seedlings. It greatly im-proves working conditions, increases labor productivity, and reduces production costs. It is of great sig-nificance to accelerate the development of the fruit industry. There will be greater market demand in the future. The development of foreign seedling lifting machines started early, and the whole process of seedling lifting operations has basically been mechanized. It can complete multiple processes such as seedling lifting, soil shaking, transportation, and collection at one time. It has better product perfor-mance advantages in the market, but the cost of the machine is also higher. After continuous optimiza-tion and innovation of domestic seedling lifters, a variety of models such as vibrating seedling lifters,large seedling lifters, and flip double-side seedling lifters have emerged, which have been able to com-plete operations such as seedling lifting soil shaking and so forth. The key parts of the seedling machine mainly include the seedling shovel and the vibrating screen. The seedling shovel is mainly responsible  for cutting off the root system of the seedlings. At present, most domestic seedling shovel uses high-quality carbon steel 65Mn as a material. After innovating and optimizing the structure of the seedling shovel, it is realized that the seedling shovel is lightweighted, the resistance of the seedling shovel to cutting soil and cutting roots is reduced, and the operating speed of the seedling shovel increases, which are the direction of the optimization design of the seedling shovel, and the seedlings will be raised in the future. In the optimization of the shovel structure, a bionic structure can be added to further reduce the working resistance of the seedling shovel and improve the working efficiency of the seedling ma-chine. During the working process of the seedling lifter, the seedling shovel is responsible for cutting the root system of the seedlings, and a vibrating screen will be added to realize the crushing and separat-ing the root from soil on the seedlings. At present, most domestic seedling lifters use grid-shaped vibrat-ing screens to complete the root and soil separation. The power source is driven by a cam linkage mech-anism or a hydraulic device. Optimizing the structural parameters and vibration frequency of the root-soil separation device can not only greatly improve the efficiency of seedling operation, but also reduce labor costs and intensity. The trend of future development is as follows. The ideal effect of separating the seedlings from the soil cannot be achieved only through the seedling spatula and vibrating screen.The emergence of the combined seedling lifter is a major breakthrough in the development of the seed-ling lifter. The combined seedling lifter refers to a multifunctional seedling lifter that can complete the processes of seedling lifting, soil shaking, transportation and collection simultaniously, which can great-ly reduce labor costs and intensity. With the improvement of domestic seedling lifting equipment and the performance of soil shaking operations, the development of multifunctional combined seedling lift-ing machine has become the trend of future development of seedling lifting machine. In the subsequent development, we can learn from the foreign relevant technical experience, combined with the actual do-mestic work site and market demand, so that the seedling lifter will be developed in the direction of higher efficiency, automation and diversified functions.