Soil Throwing Experiments for Reverse Rotary Tillage at Various Depths, Travel Speeds, and Rotational Speeds

Abstract. Submerged reverse rotary tillage was presented decades ago as a way to save energy in deep tillage, but its application was limited because it throws the tilled soil forward. The forward-thrown soil gets re-tilled, resulting in wasted energy. To understand the soil throwing process during reverse rotary tillage, a theoretical soil throwing model was established, but that model was investigated by few tests. How soil is thrown by a submerged reverse rotary tillage system is, as yet, not clear. To optimally design a submerged reverse rotary tiller, it is necessary to reveal how soil is thrown by rotary blades operating in the reverse direction. In this study, a high-speed imaging system was used to track reverse rotary tilled soil particles. Trails of soil particles from the top and middle layers of tilling were computed by regression methods. Furthermore, the original soil throwing angles and the maximum soil throwing heights were acquired by the regression equations. Experimental results revealed that the depth of the rotor shaft strongly influenced the backward-thrown soil ratio, but the travel speed and rotational speed only slightly influenced the backward-thrown soil ratio. The average original soil throwing angle decreased with rotor depth. The soil clods in the top layer had a stronger backward trend. Furthermore, a soil throwing model of reverse rotary tillage is proposed. By applying this model, some phenomena (e.g., the ratio of backward-thrown soil to forward-thrown soil at varying rotor depths) could be interpreted. Test results indicated that the assumption that tilled soil clods would be thrown along their crack direction in a reverse tillage system may be reasonable.