what is the horse power of the machine at the wheels, how much material does the leading edge of the blade push, how big is the circle, are the teeth on the inside or the outside of the circle, is the blade fully extended when rotating into the cut. If you knew the maximum force needed to move the blade when fully extended, how far the blade would be extended. So torque equals radius time force. That would give you the torque from the center of the circle to the farthest extended tip of the moldboard. Then you would have to figure how much torque you would need to ........ yeah you need an engineering forum.