Abstract:Mechanized production of dry direct-seeded and degradable film-mulched draught-resistant rice is challenged by the complexity of the seeding implements, the difficult control of mulched soil layers above the film, and the large deviation of soil thickness. A soil-bin investigation was conducted to illustrate soil movement induced by rotary till. Based on the recognized characteristic of soil movement, compromised design of rotary till, film application and soil mulching mechanisms was made to formulize the rotary-till soil-casting technology, which was further adapted to the development of a film-mulching dry direct-seeder for draught-resistant rice. Soil movement induced by rotary-till was theoretically investigated to formulize the model of soil casting and redirecting. Key parameters of the soil-redirecting plate were identified and single-parameter experiment was made on each parameters. The results from both the experiment and theoretical analysis clarified the selective ranges of the three parameters, i.e., dimensions of the soil-redirecting plate respecting to both the rotary blade rotation center and the ground level. By introducing the above-film soil covering rate and variation of the soil layer as criteria, orthogonal experiment of three factors in three levels was followed to illustrate the optimum combination of the three influencing factors. The rotary-till soil-casting technology was clarified and was then adapted to the development of a film-mulching dry direct-seeder for draught-resistant rice. Field test was then conducted to evaluate the performance of the developed seeder. Results showed that the proposed three parameters had significant influence on the performance of rotary-till soil-casting technology. The optimum combination of the design parameters were 38° for the tilting angle of the plate, 111mm of height of the plate and 362mm from the plate to the rotary blade rotation center. Such a combined set of parameters yielded the best performance of 94.2% soil covering rate and 14.8% of soil thickness variation in soil bin test. While in the field evaluation they were 94.5% and 14.8%, respectively. Rotary-till soil-casting technology was featured by 50mm shallow soil engaging and 500r/min high speed rotating, which achieved the purposes of soil-cutting and high casting, overtopping the film-applying mechanisms and soil mulching on the applied film. The findings of parameterized design of soil-redirecting plate in this work can be applied as a reference for related research in the future.
