1. A mulcher bar assembly in combination with a plow adapted to be connected to a vehicle for movement in predetermined direction, said plow having a plurality of bottoms and a beam positioned above said bottoms, said mulcher bar assembly comprising: at least two spaced apart parallel first support arms detachably rigidly secured at their forward ends to said beam and extending approximately horizontally rearwardly therefrom; at least two parAllel spaced apart second support arms, each of said second support arms being pivotally secured at its upper end to the rearward end of one of said first support arms; said second support arms having lower ends below said upper ends, the pivotal axes of said upper ends being oblique with respect to said predetermined directional movement of said plow and being above and to one side of said bottoms of said plow; an elongated bar rigidly secured to and extending between said lower ends of said second support arms; a single row of a plurality of spaced apart straight teeth rigidly secured to said bar and extending downwardly therefrom in a plane parallel to said second support arms; spring means interconnecting said lower ends of said second support arms with said first support arms so as to yieldably urge said lower ends of said second support arms forwardly; stop means on said first support arms for engaging said second support arms for limiting their forward swinging movement beyond a forward position, said second arms and said second support arms being swingable rearwardly against the bias of said springs to a rearward position wherein said teeth are disposed obliquely with respect to vertical and obliquely with respect to said predetermined directional movement of said plow when in a groundworking position.