The use of plastic film for mulching cultivation is an important agricultural production technology, which plays an important role in achieving agricultural yield increase and farmers’ income increase. China’s use of plastic mulch ranks first in the world, and China is also the country with the most severe residual plastic mulch pollution in farmland. It is of great significance to have a comprehensive understanding of the use and resource recycling of plastic mulch in China. As a result, this article reviews the recent advances in the use and recycling of plastic mulch in China. First, the types and characteristics of commonly used agricultural plastic mulch are introduced. Then, the development process and application situation of plastic mulch in China are mainly summarized, and the problems of farmland soil and environmental pollution caused by residual plastic mulch are discussed. Finally, the current situation, main practices, and existing problems of waste plastic mulch recycling in China’s farmland are explained in detail from the perspectives of government policy formulation and farmer practice. The research in this article will play an important role in further solving the problem of plastic mulch pollution in farmland soil in China and can also provide a reference for other countries.

Potato is an important food crop in China, and its planting area and output rank first in the world. Due to the labor intensity and low efficiency of manual harvesting, mechanized harvesting has become an inevitable solution for the development of the potato industry. In this paper, on the basis of elaborating on mechanized harvesting operation modes for potatoes, the research progress of key technologies, such as top-killing potato seedlings, low-loss digging with reduced obstruction, limiting the depths of rows, high-efficiency separation, sorting tons of packages, and intelligent harvesting in China and abroad, is analyzed. By comparing the basic structure and technical characteristics of both domestic mechanized potato-harvesting equipment and that used abroad, this paper identifies the gaps between domestic equipment’s performance, intelligence level, and adaptability and those of equipment in European and American countries and also identifies bottlenecks, such as large regional variability, the lack of high-efficiency and low-loss separating devices, and the difficulty of breaking through key “chokepoint” technologies. On this basis, this paper proposes that the future development direction of domestic mechanized potato harvesting should focus on the synergistic development of multiple modes, on the research and development of flexible and low-loss separation equipment, and on the integration of intelligent technology; it also gives specific suggestions, aiming to provide references for the future progress of mechanized potato harvesting.

To address the fact that existing studies may not be able to accurately describe the discrete element parameters of the soil during the potato harvesting period and to improve the accuracy of the potato harvesting equipment simulation studies, this study was conducted on the soil around the harvested potato tubers in the field. The simulation parameters of the discrete element model of soil were determined by the soil stacking angle test and soil block shear crushing test with the actual test measurements as the target. Based on a series of experimental designs, the factors affecting the stacking angle were the static friction coefficient and the rolling friction coefficient between soil particles; and the rolling friction coefficient between soil and steel. The factors affecting the maximum shear damage force were normal stiffness and shear stiffness per unit area. The quadratic regression equations were established and solved to obtain the optimal discrete element simulation parameters. The results can provide more realistic and reliable parameters for the construction of soil simulation models of potato fields during harvesting and for the discrete element simulation of soil-touching components of potato harvesting equipment. It can also further enrich the parameter data of soil discrete element simulation models and provide a reference for related research

Potato stem removal is one of the critical technical problems of potato mechanized harvesting; it directly affects the quality of potato harvesting and potato storage. There have been several studies on potato stem removal mechanisms. In practice, however, it was found that the potato stem removal rate was greatly influenced by the posture of the stem before it entered the removal mechanism. In this study, we designed a potato stem posture adjustment mechanism consisting of elastic curtains. A test rig was built to investigate the effect of curtain height, curtain width, and curtain suspension height on potato passage rate and potato stem removal rate. The Box–Behnken design (BBD), combined with the response surface method, was used to conduct the test. The optimal construction and installation parameters for each elastic curtain were determined as 278.93 mm for the curtain height, 20 mm for the curtain width, and 260 mm for the curtain suspension height. The predicted values of potato passage rate and potato stem removal rate under the optimal parameters were 92.36% and 82.83%, which were consistent with the validation test results. Based on the optimization results, a rigid-flexible coupled simulation model for a potato stem transported-posture adjustment process based on Abaqus and Adams was constructed. The maximum impact of the elastic curtain of the stem posture adjustment mechanism on the potato stem was 15.91 N and caused the stem to spring back. The projection angle β′ of the stem posture angle in the xoz plane before posture adjustment was 19.07°, and the β′ of the stem after posture adjustment was 87.18°. At this time, the stem was basically parallel to the rod of the separating sieve and had a high probability of falling from the gap of the bar to complete the removal of the stem. Overall, the stem transport position adjustment mechanism effectively adjusted the stem transported posture and improved the stem removal rate in potato mechanical harvesting.

The uneven sowing of wheat on ground covered with rice straw in the rice–wheat rotation area in the middle and lower reaches of the Yangtze River has become a serious problem. Therefore, a test bed for throwing soil after sowing with a wide wheat seed belt was designed, which could complete the functions of straw crushing, straw lateral concentration and uniform sowing at one time. The discrete element simulation model of throwing soil after sowing with a wide wheat seed belt was established with rotary blade shaft speed, soil guide plate angle and soil retaining plate angle as variables. Taking the variation coefficient of wheat sowing depth and variation coefficient of sowing lateral uniformity as evaluation indexes, the effects of three variables on sowing uniformity were analyzed by single factor test and Box–Behnken test. The results of single factor test observed that when the rotating speed of rotary blade shaft was 260–300 rpm, the angle of soil guide plate was 36°–48°, the angle of soil retaining plate was 58°–74° and the experiment of utilizing a soil throwing and covering device with a wide seed belt after sowing revealed a good consistency of sowing depth and lateral uniformity effect. The Box–Behnken simulation experiment showed that the primary and secondary factors affecting the variation coefficient of wheat sowing lateral uniformity were the angle of soil guide plate, the rotation speed of rotary blade shaft, the angle of soil retaining plate and the angle of soil guide plate. When the rotation speed of rotary blade shaft, the angle of soil guide plate and the angle of soil retaining plate were 282.1 rpm, 42.4° and 65.5°, respectively, the soil throwing and covering device after sowing has the best seed-homogenizing effect. At this time, the variation coefficients of sowing depth and lateral uniformity in simulation test and field verification test were 4.35% and 4.57%, respectively, and 12.46% and 12.73%, respectively. The results of field verification test were basically consistent with those of the simulation test, which proved that the results of applying discrete element methods to optimize the soil-throwing device after sowing with a wide seed belt were credible. This study could provide a theoretical reference for the structure optimization of a soil-throwing device after sowing with a wide seed belt.

Potato stems removal is an important part of mechanized potato harvesting. However, there is still limited research on the physical properties of potato stems, especially the determination of Poisson’s ratio and Young’s modulus. This study determined the Poisson’s ratio and Young’s modulus of the potato main stems at different heights above the ground. Since the Potato stems are viscoelastic cylinders with non-standard circular cross-sections and complex textures, the existing determination methods are difficult to apply. We propose a new method to determine Poisson’s ratio and Young’s modulus by combining image processing in the mechanical compression process. The feasibility of this method was verified by determining the hardness value of 65 Shore ‘A’ nitrile rubber specimens, and the measured Poisson’s ratio and Young’s modulus were close to the relevant literature. This method can be used for the determination of potato stems. Atlantic potatoes are widely grown for their high solids content, resistance to pests and diseases, and good processing quality. Ten Atlantic potato main stems were randomly selected at harvest time. Specimens with a length of 11 ± 1 mm were taken at 0 cm, 10 cm, 20 cm, and 30 cm above the ground from each stem. The average values of the axial Poisson’s ratio were determined as: 0.21, 0.28, 0.30, 0.32, and the axial Young’s modulus as: 15.90 MPa, 12.38 MPa, 11.68 MPa, 11.28 MPa. This study has provided critical basic data for the discrete element model construction of potato stems and numerical simulation of potato haulm killers and potato harvesters, which is beneficial for improving the harvest quality of potato. It also provides new ideas for Poisson’s ratio and Young’s modulus measurement of non-regular cross-sectional cylindrical viscoelastic materials.