Design and experiment of the anti-blocking device combined stubble burying for rapeseed direct seeding

Rice-rape rotation is often planted in the mid-lower reaches of the Yangtze River as the main winter rapeseed production area in China. But there is also the previous crop of rice straw residue and high stubble in the period of rapeseed planting. Rapeseed direct seeding machines are prone to straw entanglement, congestion, and clogging in the rotary tillage and deep fertilization, particularly for the humid and rainy climate, while the sticky and heavy plate soil. The quality of the seedbed can depend mainly on the buried cover rate of rice straw and the surface of compartments during rapeseed planting. In this study, a combined stubble burying and anti-blocking device was designed in the rapeseed direct seeding machine suitable for the high stubble, sticky, and heavy field. Two kinds of blades were included in the cylinder blade shaft in the herringbone row, including a burying stubble curved blade and a double-edged rotary blade. The burying stubble curved blade was installed in front to directly realize the deep fertilizing shovel. The soil stubble was buried at the same time. The scraping deep fertilizing shovel in front of the region also prevented the soil and straw adherence to the front surface of the fertilizing shovel. The adjacent deep fertilizing shovels were installed between the double-edged rotary blade. Both broken stubble and scraping adjacent deep fertilizing shovels were realized in the middle of the region. The soil and straw mixture clogging accumulation was reduced in the adjacent deep fertilizing shovels in the middle of the region, in order to improve the performance of deep fertilizing shovels. The counter-rotating mode was adopted to increase the operating time between the blade and the soil, in order to realize the fine crushing of the sticky soil, the burying of the high stubble, and the leveling of the compartment surface. Archimedean spiral was selected as the blade curve of the side-cutting edge on the stubble-burying curved blade. The eccentric circular arc curve was the anti-blocking straight blade. EDEM simulation was performed on the structural and working parameters of the burying stubble curved blade and double-edged rotary blade. An optimal combination was achieved, where the rotary radius of the burying stubble curved blade was 245 mm, the angle of the tangent bending line was 27°, the angle of the bending line was 125°, the width of the working width was 75 mm, the rotary radius of the anti-blocking straight blade was 275 mm, and the angle of the sharpening blade was 15°. The experiments under two working conditions showed that the rapeseed direct seeder equipped with a combined stubble burying anti-blocking device performed the higher pass rate in the high stubble and sticky surface; There was no straw winding and clay blocking, where the levelness of the compartment surface was 19.19-22.14 mm, and the straw burying rate reached more than 90%. Compared with the rapeseed direct seeding machine installed with an ordinary rotary tillage device, the levelness of the compartment surface was improved by more than 12.01 mm, and the straw mulching rate increased by more than 27.19 percentage points. The combined stubble-burying anti-blocking device shared the better performance of stubble burying and anti-blocking. The quality of the seedbed fully met the agronomic requirements for the direct seeding of rapeseed. This finding can provide a strong reference for developing seedbed preparation devices under high stubble and sticky working conditions.