Abstract: An agricultural implement with one or more pairs of knives which are eccentrically mounted on rotary knife holders and extend from the underside of a housing which can be pulled or pushed by hand or by an engine. The knives of each pair orbit in the same direction and cooperate as the blades of shears to loosen and comminute the ground. The holders are driven by a motor and the cutting edges of the knives constitute helices extending counter to the direction of orbital movement of the respective knives.