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.
