Abstract:
Abstract: To improve the seedbed quality and enhance the even distribution of soybean seeds and the consistency of deep seeding in the field, and targeting the double-row high-yield planting techniques on soybean ridges, we manufactured the profiling sliding-knife openers that could dig out V-shaped seed furrows and function as single profiling based on a self-invented double-V shape opener. This new opener can build favorable seedbeds, thereby reducing variation coefficient of qualified grain space and variation coefficient of deep seeding and improving seeding quality. The profiling sliding-knife opener mainly functions to dig out V-shaped seed furrows, improve opener passing rate by holding blades, and guarantee the consistency of furrowing depths and the even distribution of seeds. The profiling sliding-knife opener is composed of connecting bar, soil-compressing profiling wheels, profiling device, squeezing knife, and sliding knife. Interaction mechanism between squeezing knife assembly and soil as well as force condition was illustrated, sliding-knife blade force and curve were analyzed, and structure of profiling compacting wheels and force condition were elaborated. Through soil-bin trials, a three-level four-variable central composite rotatable design was applied by Design Expert software. Based on the force analysis and the actual operating condition of machine, the furrowing angle, machine forward velocity, furrowing depth and pressure were selected as influence factors. And the test index was the quantity of backfill. Experiment data obtained were assessed by the analysis of variance (ANOVA) and the quadratic regression model was set up for optimization with response surface methodology. Through the lack of fit test of the regression model, the P value of lack of fit was 0.489 5, which was larger than 0.05. The determination coefficient and adjusted determination coefficient were close to 1, which indicated that the regression equation was precise and effective. The precision was 16.449 which was larger than 4, indicating that the regression equation had sound estimation performance within the design domain. The significance sequence of influence factors on quantity of backfill from large to small was pressure, furrowing angle, machine forward velocity and furrowing depth. The optimal parameter combination of profiling sliding-knife openers was selected: load of 689.66 N, furrowing angle of 40.43°, furrowing depth of 51.62 mm, and machine forward speed of 2.12 m/s. Under these working conditions, the soil disturbing quantity by the profiling sliding-knife opener was the minimum, which indicated a humidity-improving function and a seedling-promoting effect. It could be learned from the expectation analysis that sound operating effect of ditching could be achieved when the furrowing angle was 40.43°, the furrowing depth was 51.62 mm, the operating velocity was within 2-2.3 m/s, the pressure scope was 600-700 N, and the expectation degree was close to 1. Field verification test and comparative test showed the sowing width mean absolute deviation was 4.42 after seeding by profiling sliding-knife openers, which was similar to the double-V shape opener (4.34) and smaller than the disk openers (6.55). These results suggested that under the same operating conditions, the scope of seed transverse fluctuation was smaller for the profiling sliding-knife opener or double-V shape opener versus the disk opener. The probability of seeds falling into the middle of the seed furrow was larger. The variation coefficient of seeding depth for the profiling sliding-knife openers was 6.06%, which was reduced by 10.88% compared with the double-V shape opener, smaller than that of disk openers (11.52%), indicating the seeding linearity and consistency of deep seeding were both better for our profiling sliding-knife openers. In the 50-75 mm soil layer, the soil cone index after furrowing and soil-covering by profiling sliding-knife opener, double-V shape opener and disc opener was 0.261, 0.248, and 0.165 MPa respectively. The profiling sliding-knife opener has a better operating effect compared with the double-V shape opener and disc opener. It can be used to improve the seedbed quality and sowing depth consistency, and the seedbed will be more compact, and the emergence rate will be higher.