1. The nominal working speed of the tractor at each gear is shown in Table 2. The rotary-type, crank-type and plow-type, with similar rated power were used for this study. Each rotavator had different types of blade: the rotary-type had ‘C’-shaped blades, the plow-type had triangular-shaped blades, and the crank-type had trapezoidal-shaped shovel-type blades. A view and specifications of each