An earth working apparatus comprising a wheeled vehicle capable of traversing the ground and a ground breaking assembly mounted on the front end of such vehicle, such ground breaking assembly comprising a cylinder mounted for movement with the vehicle and for rotation about its cylinder axis, such cylinder having teeth projecting from its cylinder surface; the ground breaking assembly also having a shield partially surrounding the cylinder and provided on its inner surface close to the cylinder with fracture boards against which large pieces of pavement, frozen earth or stone impact, thereby causing such large pieces to fragment.