Optimization of energy use and torque in vertical axis rotary tillers: effects of disc diameter and blade number on tillage performance

<jats:p>Efficient soil management in vineyards with stony, loamy–sand soils is crucial for energy conservation and sustainable production, particularly in organic systems where herbicide use is restricted. Rotary tillers with vertical axes are widely used for intra-row and near-trunk tillage but are often limited by high energy demand. This study aimed to develop a mathematical model to optimize the operating regime of rotary tillers by evaluating the relationship between torque resistance, which is the key energy indicator, and primary kinematic parameters: disc rotational speed and diameter. Field experiments were conducted at the Voskehat Experimental Station in Armenia using a two-factor, second-order central composite design. Torque was measured with a high-precision strain-gauge system, and two groups of L-shaped blades (Z₁ = 3 and Z₂ = 4) were tested. Regression analysis showed that disc diameter had a strong linear effect on torque, while rotational speed exhibited a weaker influence that varied with blade number. In all cases, torque variation did not exceed 10 N·m within the speed range of 16.5–20.5 s-1. Distinct functional patterns of torque variation were observed depending on blade number, likely reflecting the interaction between soil deformation wave propagation and disc rotation. Defining the optimal operating regime, therefore, requires minimizing torque while ensuring that the kinematic parameters satisfy agrotechnical requirements, thereby preventing excessive soil pulverization, reducing erosion risk, and ensuring high-quality tillage.</jats:p>