Abstract: An elongated rigid bar is arranged to be secured at one of its ends to a power unit and is enclosed through most of its length in a rigid housing. Longitudinal passageways are provided interiorly of the housing for receiving a cross link drive chain trained over a sprocket on the power unit and on a cross shaft supported at a free end of the housing. The cross shaft supports digging units. A ground engaging support wheel is attached to the housing adjacent its free end. The housing has a semi-flexible guard mounted on it adjacent the digging units.