A compacting device of rice dry direct-seeding planter based on DEM-MFBD coupling simulation significantly improves the seedbed uniformity and seedling emergence rate

The rice dry direct-seeding planting mode is a typical shallow sowing operation, and the traditional compacting mechanism with only longitudinal profiling ability is difficult to ensure the seedbed uniformity, resulting in the seedling emergence rate always lower than 80%. This study innovatively proposed a novel bidirectional-micro-profiling compacting device (BMPCD). In this study, the coupled DEM-MFBD simulation technique was utilised to find that the core design parameters k (elasticity coefficient of the reset spring) and t (thickness of the elastic sheet) of the BMPCD would significantly affect the seedbed uniformity by changing the resistance value F_r during the profiling process (P ≤ 0.01). The simulation results showed that when k was taken as 7.8 N mm⁻¹ and t was taken as 1.6 mm, the seedbed uniformity could be most greatly improved. The field experiments showed that compared with the bidirectional profiling compacting device (BPCD) and longitudinal profiling compacting device (LPCD), BMPCD could reduce the coefficient of variation of soil firmness (CVSF) by 33.1% and 40.1%, and the coefficient of variation of sowing depth (CVSD) by 37.1% and 51.8%, respectively, and then improve the seedling emergence rate of dry direct-seeded rice by 5.8% and 12.2%. This indicated that bidirectional and micro-profiling compaction technology could tackle the problem of low seedling emergence rate in rice dry direct-seeding. Meanwhile, the results of the DEM-MFBD coupling simulation were not significantly different from the test results of the field experiments (P > 0.05), indicating that it could be used as an efficient and accurate new method to study the dynamic characteristics between the soil and machinery.