A depth adjustment assembly for a disc opener or other furrowing device has an eccentric cam with an outer surface that engages and thus prevents rotation of a gauge wheel arm. As rotation of the gauge wheel arm sets the relative position of a gauge wheel relative to the furrowing device, preventing rotation of the arm sets the cutting depth for the furrowing device. The eccentric cam may have a smooth outer edge defining an indiscrete range of positions or a profile outer surface that defines discrete depth setting positions. The eccentric cam is biased into engagement with a receiver by a pin and spring, but overcoming the bias allows the cam to be momentarily disengaged and rotated to reposition the eccentric cam.
