Development and Physiological Cost Evaluation of a Modified Blade System for Power Weeder in Dry Land Cultivation

The introduction or development of mechanical weeders was a cost-effective and safe approach for weed-management in dry land cultivation. In this study, the existing power weeder was evaluated in the farm to assess their performance. Entangling of the weeds in the blade unit was commonly noticed for the power weeder causing reduced weeding efficiency and increased labour requirement. Hence modification is done by changing the rotary blades as helical blades to improve the penetration in the soil and there by removing the weeds effectively. The cardiac cost involved in the operation of the modified power weeder was found out and the mean working heart rate of the subject was 102 beats min-1. The corresponding value of energy expenditure was 14.35 kJ min-1. The human energy expenditure was reduced to the tune of 36% after modification. The predicted oxygen consumption rate was 0.8497 l min-1 that is 41% of their aerobic capacity (VO2 max) which was above the acceptable limit of 35% of VO2 max. Mean overall discomfort rating on a 10 point visual analogue discomfort scale ( 0- no discomfort, 10- extreme discomfort ) was 5.0 and scaled as "moderate discomfort" before modification where as ODR was 4.0 and scaled as "more than light discomfort" during operation of modified power weeder. The weeding index was found to be 85%. If only one worker is engaged for the weeding operation with this equipment, 5 min rest could be provided after 30 minutes of working. Based on the mean energy expenditure, the operation was graded as ?Moderately Heavy?.