Performance Evaluation of Power-Operated Maize Sheller for Small and Marginal Farmers Based on Physiological and Subjective Workload Assessment

This study evaluated the ergonomic suitability and operational performance of a power-operated (0.75 kW) maize sheller for small and marginal farmers under real on-farm conditions. An ergonomic assessment was conducted through physiological workload measurements, including heart rate, oxygen consumption rate, and energy expenditure, as well as a subjective workload evaluation using the National Aeronautics and Space Administration Task Load Index (NASA-TLX). Ten agriculturally experienced participants operated the machine under standardised conditions. The results indicated a moderate physiological workload, with an average working heart rate of 103 bpm, oxygen consumption rate of 0.50 L min^-1, and energy expenditure of 15.46 kJ min^-1, suggesting acceptable physical demand during operation. The NASA-TLX analysis showed higher temporal and mental demands than physical demands, indicating that task pacing and operator interaction influenced perceived workload more than physical effort. Users reported good portability, operational safety, and ease of use; however, dust generation during operation was identified as a factor affecting operator comfort. The machine achieved a shelling efficiency of 98.05%, a grain damage of 2.92%, and a shelling capacity of 119.4 kg h^-1, demonstrating improved productivity while maintaining a manageable ergonomic workload. Overall, the findings indicated that the power-operated maize sheller can reduce labour drudgery and enhance post-harvest efficiency while maintaining an acceptable comfort and safety conditions for smallholder farming systems.