The experiment was conducted at BRRI regional station at Rajshahi and Rangpur in 2012-13 Boro seasons. Boro rice was planted after harvesting Aman rice. The planting method of Boro rice in this region is mostly in row. The rice harvesting was performed both manually (with sickle) and mechanically (with reaper). The BRRI developed self-propelled reaper and imported Chinese reapers were used for harvesting. The cutting widths of both the machines were 1.2 m. The cutting height of the reapers could be adjusted from 0.15 to 0.60 m. The following factors were considered to evaluate the performance of both reapers:
Walking speed (forward speed): For measuring forward speed of self-propelled reaper, while harvesting crop, the distance of the reaper traveled in 30 minutes was measured and the speed of travel was recorded in terms of km/hr.
Operating time and cutting area: The starting and finishing times of harvesting in each plot were noted. A total area of 0.232 ha (57.29 decimal) and 0.223 ha (55.16 decimal) of BRRI dhan-28 were harvested in 60 minutes by the Chinese reaper at Rajshahi and Rangpur, respectively. On the other hand, a total area of 0.271 ha (67.02 decimal) and 0.263 ha (65.02 decimal) of BRRI dhan-28 was harvested during same time by the BRRI reaper at Rajshahi and Rangpur, respectively.
Fuel consumption: Before starting the harvesting operation in the test plot, the fuel tank of the reaper was filled up to its full. The quantity of fuel required to fill the tank fully after harvesting the plot was measured to determine the quantity of fuel consumed for reaping the test plot.
Field capacity: Field capacity of a machine is the actual rate of land preparation/harvested or crop processing in a given time, based on total field time. In other wor ds, effective field capacity of a machine is a function of the rated width of the machine. The percentage of rated width actually utilized the speed of travel and the amount of field time lost during the operation. In order to determine effective field capacity the rated width of the implement (cutting width), speed of travel and field efficiency were measured. Field capacity and field efficiency were calculated using the following formula (Hunt, 1973):
Field capacity , C = A/T................... ...... (1)
Where, C = field capacity (ha/hr)
T = total time for the reaping operation (hr)
A = area of land reaped at specified time
Harvesting cost: The costs of harvesting with reaper are classified into two categories: fixed cost and variable cost. In order to compare harvesting costs in manual and reaper methods, all the costs of wages in manual and the fixed and variable costs in mechanical operations were calculated. Fixed cost included depreciation cost, interest, shelter and taxes and is a function of purchase value, useful life and interest rate. Annual interest was calculated on average investment on the machine over its full life. Depreciation was determined by straight - line method by the following equation:
Depreciation, D = (P-S)/L............................ (2)
Where, D= Mean yearly depreciation (Tk./year)
P= Purchase value (Tk.)
S= Salvage value (Tk.) L = Useful life (year)
Useful life for power tiller was considered to be 10 years and this is assumed to hold for the reaper. T he purchase price of BRRI developed self - propelled reaper was considered as Tk. 1, 20,000. On the other hand the market price of imported self - propelled Chinese reaper was Tk. 2, 20,000. The machine salvage value was considered to be 10% of purchase value. Interest is an actual cost in agricultural machinery and was determined by straight line method by the following equation:
Interest, I = {(P+S)/2}X i............................... (3)
Where, I= Mean interest (Tk. /yr)
P= Purchase value (Tk.)
S = Salvage value (Tk.)
i= interest rate (%)
The insurance and shelter costs were 3% of purchase value. Variable costs include fuel, lubricant, repair and operational costs and are directly related to the amount of work done by the machine. Repair cost for reaper power tiller was considered 3.5% of purchase value for every 100 hours of effective operation. Lubricant cost is 25% of fuel cost. The fuel cost (Diesel) in retail market was considered as Tk. 65 per litter. The wages of labour in manual method of harvesting using sickle was also calculated and it was Tk. 350 per day (eight hours of working day). For agricultural machinery, the interest rate is considered to be 15% of purchase value. Fixed cost was calculated as: Fixed cost, FC = Depreciation + Inter est on investment + Tax, insurance and shelter
Break - even analysis: The break - even point, the area that a machine has to work per year in order to justify owning the machine, was determined by the following equation (Alizadeh et al., 2007):Break - ev en point, B = F/(Va-Vm) (4) Where,
B= Break – even point (ha/year)
F= Fixed costs of Machine (Tk./year)
Va = Variable costs for manual method (Tk./ha)
Vm = Variable costs for machinery method (Tk./ha)