Torque and energy characteristics for strip-tillage cultivation when cutting furrows using three designs of rotary blade

Strip-tillage research in developing countries usually relies on commonly used rotary blades designed for conventional full disturbance soil tillage. With the aim of optimising the blade geometry and operational settings, this study investigated the effect of three blade geometries (conventional, half-width and straight) at four rotary speeds (125, 250, 375, and 500 rpm) on torque, power and energy characteristics. A single row rotary tiller was fitted with the blades set at a cutting width of 50 mm and depth of 50 mm and tested in a soil bin (sandy loam soil). Analyses of high speed video images and corresponding blade motion revealed that the peak torque occurred at a higher blade penetration depth as the speed increased indicating transformation of the peak torque requirement from due to initial soil failure at a low speed to final soil cutting and throwing at a high speed. The straight blade design required the least torque, average power, peak power, specific energy and effective specific energy at 375–500 rpm which targeted for a small bite length for a fine soil tilth. The straight blade saved 20–25% power when compared with the conventional and half-width blades at 500 rpm. Although, the average power, peak powerand specific energy requirements increased with the rotary speed for all the blades with a steep rise over 375 rpm, the effective specific energy requirement remained almost unchanged for the straight blade indicating its high effectiveness for strip-tillage operations. •Torque requirement was dependent upon rotary speed rather than the blade geometry.•Peak torque requirement was at least twice the average torque for any blade geometry.•Power and specific energy requirements increased with rotary speed (all blades).•Straight blade design saved 20–25% power over conventional blade at 500 rpm.•Effective specific energy remained low for straight blade even at high speed.