Animal power still plays an important role in Indian agriculture. Despite having a good scope, animal power has not been fully exploited for weeding and interculture operations. Four basic shapes of weeding tools, namely, straight blade, curved blade, triangular blade and sweep have been identified, tested and optimized for use in black soils. Improved blades have been introduced in animal drawn weeders.
For straight blades, optimum rake angle (ä) of ??20.6° to 22.5° and minimum blade width (B), thickness (t) and sharpness angle (ö) permissible considering mechanical strength were recommended. For curved blades of 200 mm working width, optimum radius of curvature (R) was 136.4 mm and rake angle (ä) ranged from 22.0° to 22.4°. For triangular blades, optimum rake angle (ä) ranged from 21.6° to 21.9° and approach angle (á) ranged from 76.9° to 81.6°. Optimum values of rake angle (ä) for straight, curved and triangular blades were close, within the range of 20.6° to 22.5°. The average value of the optimum rake angle for all these blades was 21.93°. For sweeps, optimum values of tool parameters were: approach angle (á) in the range 74.7° to 75.0°, wing width (W) of 50mm and below and blade thickness (t) of lessthan 4 mm. Considering the optimum values of approach angle (á) for both triangular blades and sweeps, the average was 78.6° (n = 24, ó = 1.9), which was significant within 36 limits. Field performance of cultivators using optimum tools, assessed through performance index, was encouraging and substantiated the laboratory findings.
