| Resumo: |
An existing 1.5kW brush cutter was modified and evaluated with the view to adapt a low-cost rice harvesting machine. The modifications included replacing existing blade with circular saw blade, incorporating a guider and a driver to lay down the harvested crop in swath and attachment of a harness belt for easy and comfortable operation. The machine was evaluated keeping in view major influencing factors i.e., crop establishment (conventional transplanting, system of rice intensification (SRI), and mechanical transplanting), blade type (B1: 40 teeth, pitch 1.92 and B2: 80 teeth, pitch 0.96) and straw moisture content (38-42, 33-37 and 28-32%, w.b). The results showed that the height of cut was significantly affected (p<0.05) by the crop establishment and blade type however straw moisture content did not have significant effect on height of cut. The height of cut for the machine with blade B1 ranged from 21.40-31.95 mm for different crop establishment; which was much lower than existing reapers/combines. Fuel consumption increased with decrease in row to row spacing or increase in plant population per m2 area giving rise to the trend: SRI < mechanical transplanting < conventional transplanting and decreased with decrease in straw moisture content. Cutting efficiency was higher under mechanical transplanting/SRI over conventional transplanting because of symmetrical transplanting of rice. With respect to straw moisture content, cutting efficiency was highest at moisture content of 33-37%, because of desirable turgidity of the straw. The grain loss was negligible for all the treatment combinations. The results showed that the field capacity of the machine ranged from 0.031-0.033 ha.h-1 under different crop establishment. Resting cycle was found to be 10 minutes for every 30 minutes of work. The benefit-cost ratio, payback period and breakeven point were determined as 1.35, 74.91h and 0.134 ha, respectively for the portable rice harvester. The developed harvesting machine was able to harvest the rice crop when fitted 40-teeth circular saw blade having carbide tip. A machine of this kind is a positive development in rice harvesting especially for small and marginal land holdings.
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