A low-cost simple power tiller front-mounted spike tooth type mobile maize open cover has been developed in Farm Machinery & Postharvest Process Engineering Division of BARI, Gazipur 2015 with a view to easy way open cover maize in the farmers’ field of rural areas and eliminating botheration of transportation of traditional maize open cover from place to place. The main components of the open cover are hopper, rotating cylinder, concave, grain delivery outlet, open covered cob delivery outlet, open cover fixing arrangement, main pulley with power transmission arrangement.
The maize open cover is hitched in front of the two-wheel tractor with an engine base through nuts and bolts. There is a flexible stand bottom part of the base frame which facilitates standing maize open cover in a level position. Before starting open covering operation, the outermost two “ V” belt released from the flywheel and introduced another two special “V” belts and fixing flywheel of the 2WT and main pulley of the mobile maize open cover. The cross-section of the mobile maize open cover. The maize open cover was tested in the research farm of BARI, Gazipur two separate dates of May 2016. The maize was collected from experimental plots of Irrigation & Water Management Division, BARI Gazipur and Plant Breeding Division of BARI Gazipur. The harvested maize was dried on an open floor and relevant information recorded. Data to be collected: The following data to be recorded for evaluating the mobile maize open cover performance. (i) Cob-kernel ratio (ii) Moisture content, %, (iii) open covered grain, kg (iv) Broken kernel, kg (v) Un open covered grain, kg (vi) Speed of rotating cylinder, rpm, (vii) Time of operation, min (vii) Fuel consumption, l/h , (viii) Cost of operation. Data to be analyzed – open covering capacity, kg/h; open covering efficiency, %; open covering loss, %.
Calculation of technical parameters: Technical parameters were calculated as per the report of performances of existing maize open cover in Bangladesh ( Alam and Momin, 2009).
Kernel-cob ratio
Ten un-open covered cobs were collected and weighed. After open covering manually, the kernels were weighed and subtracted from the total weight for cob weight. The kernel-cob ratio was calculated as
KCR = KW / CW. Where, KCR = Kernel-cob ratio, KW = Kernel weight, kg; CW = Cob weight, kg.
Cost Calculation: Cost calculation was done on the basis of fixed cost and variable cost of the mobile maize open cover. The related cost parameters were as follows. (i) Purchase price of the open cover (ii) Salvage value of the open cover (iii) Machine life, year (iv) Bank interest rate, % (v) Open cover annual use, hrs (vi) Operator charge, Tk./day (vii) Fuel consumption, lit/h (viii) Repair and maintenance cost and (ix) Power tiller hire price for maize open cover operation. Cost of custom hire rate was also recorded for cost comparison. Thus, the total cost of planting was the sum of fixed cost and variable cost of the maize open cover (Anonymous, 1991).
AC = FC + VC
Detail cost calculation for the maize open cover was given in Appendix IV. Net benefit was also calculated as deducting cost from total benefit.
Annual Costs: Annual costs are determined by summing up fixed cost and variable costs. The two parts of the following equation represent the fixed cost and variables costs, respectively. The part (A/EFC) represents the approximate hours of use per year. The equation of annual cost can be rewritten again as following for annual cost estimation.
AC = FC + {(A / EFC x (R&M +L+H)}. Where, AC= annual cost of open cover operation, Tk./yr
EFC= effective capacity of maize open cover, ha/hr
A= annual area use, ha
L= labor wage, Tk/hr
H= power tiller hire price, Tk./hr
R&M= repair and maintenance cost, Tk./hr