Analysis and experiment on working performance of disc coulter for no-tillage seeder

Abstract: Compared with traditional tillage, conservational tillage-also known as zero tillage can effectively prevent soil from wind and water erosion, resist spring drought, prevent sandstorm, increase crop yield, and save cost. No-tillage planter is an important agricultural implement for conservational tillage. In northeast China where ridge culture is the primary planting mode for maize production, the highly effective stubble-cutting device is required because the soil in this region is often covered by hard stubble and a small amount of stalks. Stubble-cutting device is one of the key components affecting performance of no-tillage planter. Two kinds of stubble-cutting device are commonly used, including power-driven device and passive one. Power-driven device can smash stubble and create good seedbed, but is also associated with soil disturbance, high power consumption and blade wear. Passive device of simple structures consumes less energy and only causes slight soil disturbance. Among them, rolling types of disc stubble-cutting coulters can easily cut through stubble under the soil surface without throwing stubbles out of the soil, so it is suitable for application in Northeast China. There are few studies on cutting velocity and working resistance of dis coulters. However, an understanding of cutting velocity and working resistance of dis coulters is necessary for design and application of dis coulters. Therefore, this study investigated the cutting velocity under the condition that coulters slides occurred, and working resistance in vertical direction as well as tractive resistance by kinematics and force analysis, the influence of auxiliary weight and unit working speed on stubble-cutting depth of three disc coulters (plain, wavy, and turbo) in single factor field experiments, and the influence of disc coulter type, auxiliary weight and unit working speed on tractor resistance in an orthogonal field experiment of three factors and three levels. Both theoretical analysis and field tests showed that the coulter slippage had negative effect on the cutting velocity during the stubble-cutting process, which suggested reducing the coulter slippage to the greatest extent in the application of dis coulters. The tractor resistance of coulters changed slightly during the process of cutting soil in an increasing and then decreasing trend during the process of stubble cutting. The cutting depth of the three coulters increased with increasing auxiliary weight. When the auxiliary weight was less than 48 kg, the cutting stubble depth of plain coulter was largest, followed by the turbo coulter as well as the wave coulter. In practice, stubble under the ground must be totally cut through in order to make sure that no-tillage planter could be in good operation. To obtain a cutting depth of 80 mm or above, the minimum auxiliary weight of the plain, wavy and turbo disc coulter was required to be 48, 72 and 60 kg respectively. Since the total weight of force-measuring device and general frame was 100 kg, the down pressure acted on the plain, wavy and turbo disc coulter should be not less than 148, 172 and 160 kg in order to acquire enough cutting depth in designing no-tillage planter. The tractor resistance increased with increasing unit working speed, and could be affected by auxiliary weight > unit working speed > coulter types. With minimum auxiliary weight, the least tractor resistance of plain coulter, turbo coulter and wave coulter was 2.52, 2.65 and 2.75 kN, respectively. This study provided valuable information for the design and application of disc coulter and no-tillage planter.