Determination of Power Required by a Rod Digger in Onion Harvesting

One method for digging onions up during harvest operation is using a rod cultivator in which, combination of rotational and linear movements of the rod underneath the bulbs, dig the onions out. Total power consumed by rod cultivator comprises two parts; one for driving the rod, and the other, for pulling the rod along the field. Travel speed as well as operation depth (depth to width ratio) of onion rod digger are both important factors that affect the total power consumption. In the present research, the effect of travel speed as well as operation depth on power demand of an onion rod digger was studied using a split plot in randomized complete block design with three replications. The treatments were operation depth in two levels, namely, 5-7 and 10-12 cm as the main plots and travel speed in three levels, namely, 0.3, 0.4 and 0.5 m/s as the subplots. During each treatment, draft force, drawbar power, torque and rotational power were measured. Based on results, draft force and drawbar power were between 4865 and 6400N, and, 1857.5 and 3125.5 W per meter of work width, respectively. In addition, the measured torque and rotational power were between 25.2 and 35.1 N.m, and, 1079 and 1814.5 W per meter of work width, respectively. Considering 2 m of work width for onion digger, tractors capable of delivering about 6.5 kW of drawbar power and about 4 kW of PTO power, are able to run onion digger. Most of the tractors currently used by farmers in Iran, fall within this category.