An anchoring device for a self-propelled irrigation system includes a drive assembly that drives a soil auger into the ground to anchor a drive tower of the irrigation system. The soil auger is rotatably driven about a vertical axis and movable vertically relative to the drive tower. The soil auger includes a lower tip, a multi-sided head at an upper end, and a helical screw portion between the lower tip and the upper end. The drive assembly includes a sleeve member with an inner surface that mates with the head of the soil auger and allows the soil auger to slide within the sleeve member while rotating together with the sleeve member. A bit cleaner assembly is arranged to engage the helical screw portion of the soil auger to clean soil from the auger and to cause the auger to move vertically relative to the sleeve member upon rotation.
