Abstract: The torque characteristics and the specific tilling energies of three commonly used rotary blades in Thailand, i.e. the Japanese C-shaped blade, the European C-shaped blade and the European L-shaped blade, were studied to develop a suitable rotary blade for seedbed preparation in Thailand. The experiments were carried out in a laboratory soil bin at forward speeds of 0.034, and 0.069 m/s, and rotational speeds of 150, 218, 278 and 348 r/min (or 3.30, 4.79, 6.11 and 7.65 m/s) in sandy loam and clay soils. The results showed that the shape of the rotary blade influenced the torque characteristic and the specific tilling energy. For the Japanese blade, since its lengthwise curved portion tilled the soil first, the increase of tilling torque was less than the other two blades. For both European blades, the curved portion along the length and the tip was the first to impact the soil mass. The cyclic variation in torque could be observed distinctively, especially, for both European blades. The investigations indicated that the specific tilling energy of the Japanese C-shaped blade was the highest while the specific tilling energy of European L-shaped blade was the lowest.