Abstract:
Potato is secondary non-cereal crops in Ethiopia, in which round 1,288,146 household farmers depend on it. Potato harvesting was practiced using animal-drawn local Maresha and hand hoe, which is characterized by high man-hour requirement, drudgery and considerable losses in terms of tuber damage and inefficient exposure. Thus, it was important to consider a small horsepower tractor-drawn potato digger for Ethiopian smallholder farmers and, a single axle tractor-operated potato digger elevator was designed, fabricated and evaluated. The major parts of the potato digger were a soil-cutting blade, shanks, chain and rod conveyor, depth control wheels, drawbar hitch, transmission system, toolbar, and eccentric discs. Some physical and mechanical properties of the tubers and soils, relevant to the design of the digger were also studied. Tubers of Belete potato variety widely grown in the country were used for performance evaluation. The experimental design used was laid in a split-plot where conveyor slope (10o, 15o and 20o) was the main plots; the rake angle (15o, 20o and 25o) was sub-plots with three replications as a block. The prototype machine was evaluated to see the effect of the slope and blade angle on the performance of the prototype in terms of different parameters. Tuber damage loss decreased when increasing the rake angle but increased with conveyor slope. The maximum exposure efficiency of 96.47% was obtained when the machine was operated at a conveyor slope of 15o and the rake angle of 20o. Increasing the rake angle and conveyor slope up to 20o and 15o respectively, resulting in increased exposure efficiency, and it declined gradually at 25o and 20o rake angle and conveyor slope, respectively. At this optimum condition, damage percentage, conveyance efficiency, cleaning efficiency, drawbar pull, fuel consumption, wheel slip, soil swelling factor, soil mean weight diameter, pulverization ratio, and field capacity were 3.39%, 89.64%, 91.87%, 2959.1N,14.87 l.ha-1, 17.67%, 20.25%, 17.44 mm, 78.09% and 0.127 ha.h-1 respectively. From these performance indicators, it can be concluded that the prototype machine is very acceptable with a high prospect for adopting for small and medium-scale farmers
