Characteristic loading of light mouldboard ploughs at slow speeds

A study on four mouldboard ploughs, that are commonly used with animal traction in Kenya, was conducted. Draught, suction and torsion loads were measured and specific draught evaluated in field tests on four sites with typical agricultural soil conditions. Draught and suction are the horizontal and vertical components of the reaction to soil force, respectively, while torsion is the resisting moment about the plough shank. The objective was to quantify these parameters and to study their characteristics under variable conditions at operation, at speeds up to 1.12 m/s and tillage depths between 0 and 150 mm in an attempt to optimize the design, selection and utilization of mouldboard ploughs for animal traction in Kenya. It was found that depth of tillage is the most critical factor, and draught and suction increased significantly with depth while specific draught increased or decreased depending on the soil type. Draught and specific draught increased significantly with speed. The increase in suction with depth probably implies an increased stability in the ploughing operation, while its reduction with speed indicates a potential instability of plough control with varying speeds. Consequently, aiming for steady motion in the utilization of animal traction may aid in the optimization. It was also found that ploughs with a high specific draught (kN/m) are expected to experience higher torsional loads on the shanks. The characteristic draught, specific draught and suction loads of the ploughs were described by quadratic functions in speed and depth of tillage with coefficients of determination (R₂) ranging from 0.55 to 0.99. A significant difference in the coefficient of variation of draught loads in the three soil types probably implies that optimal duration for use of animal traction in tillage should be dependent on soil type.