An excavation bucket assembly (10) is mounted to a tractor. A soil gathering trenching blade (48) is supported by an upwardly extending rear wall (18) and is movable down through a soil receiving opening (32) to scoop soil from beneath the ground wall (16) of the bucket, with the opening (32) being placed rearwardly of the front edge (30) of the ground wall, providing adequate space in the soil collection chamber (28) for receiving the excavated soil.