Design and experiment of active straw-removing anti-blocking device for maize no-tillage planter

Abstract: Conventional farming methods with multiple operations by multiple types of machinery may lead to serious shallow soil hardening and cost increases for wheat-maize rotation cropping areas in Huang-Huai-Hai Plain of China. In addition, there are several technical problems for the traditional maize no-tillage planter when seeding in the fields covered by heavy wheat straw, 1) soil-buried parts of the no-tillage planter are easy to be blocked by the wheat straw, which cannot guarantee the smooth operation; 2) the seeds may be improperly planted on the top of wheat straw since the soil is totally covered by the wheat straw; 3) the germinated seeds cannot grow up normally as no soil covered, which result in production declines. In the current study, an active anti-blocking device was designed for the maize no-till planter for removing wheat straw that covered on the soil surface. During seeding in the field, the wheat straw that covered on the surface was disrupted and thrown into the air by the device and was transferred backward before it landed. Then, the planter would ditch, fertilize and seed in the cleaned field produced by the device. At the last, the smashed straw was evenly covered on the fields after planting. The structural parameters and motion parameters of the anti-blocking device were determined based on a simulation model built by the discrete element method （DEM）. The model was composed of soil, full-coverage straw, and device, which can be used to simulate the process of removing the unsupported straw from the soil surface. The model and interaction system was established in EDEM 2.6 simulation environment, and their physical properties were calibrated with the real properties of lime concretion black soil and wheat straw. According to theoretical design to set simulation parameters, the radius of the cutter head was set to 120 mm, the driving speed of the cutter shaft was set to 500 r/min, and the depth of the cutting edge was set to 10 mm, the operating velocity of the active anti-blocking device was set to 4 km/h.The simulation experiment was used to analyze the displacement and the clearance rate of straw for selecting suitable structural parameters and motion parameters for design. The simulation results indicated that the tangential force of the cutting edge was irregularly fluctuating with time, and the average tangential force was 5.8 N; the straw clearance rate was 98.5% in the disrupted zone, the average width of the area without straw was 245.5 mm according to the random sampling, which was in accordance with the requirement of ditching, fertilizing, and seeding. The field experiment was carried out by a straw-removing maize no-tillage planter with the designed anti-blocking device mounted, for ditching, fertilizing and seeding, within a field covered by 1.24 kg/m2 wheat straw with stubble height of 40 mm. The planter was hauled by a high-power tractor of over 55 kW with an operating velocity of 4 km/h and a working width of 2 400 mm, resulting in a pure productivity of more than 0.56 hm2/h. The field experiment and measurement results showed that the straw-removing no-tillage planter with an active anti-blocking device had a stable operation that can significantly improve the seeding environment. The number of clear straw was 0, the straw clearance rate was 90.21%, and was 8.29 percentage points off the simulated value. This study illustrated that the maize no-tillage planter with active anti-blocking device was suitable for removing the covering straw, cleaning the seedbed, fertilizing, and covering the seedbed with wheat straw. Meanwhile, the research provides a reference for the design and extending of the no-tillage planter for the fields with full coverage of straw.