Optimization of Performance Parameters of Onion Digger with Cutter Bar Topping Unit

A tractor-operated onion digger with cutter bar topping unit was developed for multiple operations, i.e., topping, digging, soil separation and windrowing of onions in a single pass. The physical and agronomical properties of onions are computed such as equatorial diameter, polar diameter, shape index, bulk density, plant height and number of tillers per plant which were measured and found to be 44.75 mm, 43.34 mm, 1.01, 561 kg/m 3 , 28.76 mm, 5 number, respectively. Field evaluation of the developed machine was conducted to optimize the independent parameters such as moisture content (9.5, 11.65 and 13.0%) (d.b.), rake angle (10°, 15°, 20°) and speed of operation (2.5, 3.25, 4.0 km/h) on three responses, i.e., digging efficiency, damage percentage and topping efficiency in response surface methodology by using central composite design in Design Expert software. The optimum conditions for highest digging efficiency (93.76%), minimum damage percentage (6.44%) and maximum topping efficiency (78.46%) were found at 11.39% (d.b.) moisture content, 15.12° rake angle and 3.11 km/h speed of operation, respectively. For optimum values of independent parameters, the field efficiency, actual field capacity and theoretical field capacities were found to be 85%, 0.17 ha/h and 0.20 ha/h, respectively.