Clod crumbler

A rotary clod crumbler device mounted for forward movement along the ground, the device comprising inner and outer soil-treatment rotors mounted for rotational movement about a common axis lying transversely to the direction of forward movement of the device, the outer rotor having elongate soil-engaging parts extending transversely to the direction of forward movement of the device, the inner rotor having soil-engaging parts extending radially of the common axis and drive means operative to drive the inner rotor in the same rotational sense as the outer rotor but at a different peripheral speed thereby to impose shearing forces on soil simultaneously engaged by the parts of the two rotors.