Based on the production of maize, the use of maize sheller and concentration of the manufacturers of maize sheller, five distinct locations or clusters were selected for this study. The locations were Bogra, Rangpur, Dinajpur, Rajshahi and Jessore. The study was conducted during the period of 3 September 2006 to 30 March 2007. Detail field performance tests were conducted during 16 – 22 October 2006 on seven selected maize sheller models of three categories such as spike-pinion type, spiral rasp-bar cylinder type and parallel rasp-bar cylinder type to asses the comparative technical and financial performances. The technical performance was studied during 16 – 22 October 2006. The maize used for the study were harvested from two different plots having moisture contents of 17% and 21% wet-basis and the cob-kernel ratio of 1:3 and 1:4, respectively. The days were sunny and the temperature varied between 25 – 38oC with a relative humidity of around 55%. Same threshing floor, operator, labour and similar operating conditions were carefully maintained during evaluation of the technical performance of the maize sheller models. Kernel-cob ratio, Kernel and cob moisture content, Shelling capacity, Throughput capacity, Cylinder loss, Separating loss, Spilled kernel loss, Shelling efficiency, Broken Kernel were calculated using standard procedure. Economic parameters calculation, eg., fixed costs, variable cost,operating cost of maize sheller, cost of shelling were done. Also, partial budget was calculated.
Break-even use
The following formula was used to estimate th e appropriate “break-even” use of selected maize sheller:
Break-even use (ton) = Fixed cost of the sheller for entire economic life (Tk)/{Hiring rate of the sheller (Tk/ton) – Variable cost of the sheller (Tk/ton)}
Where, Fixed cost of the sheller for entire economic life (Tk.) = Annual fixed cost of the sheller (Tk./yr) x Economic life of the sheller (yr)
Benefit cost ratio (B/C)
Benefit cost ratio was defined as the ratio of gross revenue to shelling cost (expressed either in % or in annual worth).
B/C ratio = Gross revenue (Tk./hr)/Shelling cost (Tk./hr)
Calculation for gross margin (GM) and net margin (NM)
The gross margin was calculated as gross output less total variable costs and net margin (NM) was calculated as gross margin (GM) less fixed costs (FC).
Gross revenue = [Units] × [Hiring rate per unit]
Gross Margin = [Gross output] – [Total variable cost]
Net Margin = [Gross Margin] – [Fixed costs]