If you have a tractor than can drive over them a flail mower should work. If you intend to mow anything on the property it would be worth looking into a flail mower because they're very useful (and can also be used to shredfallen timber and for light brush clearing). We used to have one for the orchard and used it to reduce the debris from trimming shelter belts as well as mowing between rows ("debris" being anything up to 10cm thick, you just mow along the length a few times and then it's woodchips).

If you have a tractor that can drive over them a flail mower should work. If you intend to mow anything on the property it would be worth looking into a flail mower because they're very useful (and can also be used to shred fallen timber and for light brush clearing). We used to have one for the orchard and used it to reduce the debris from trimming shelter belts as well as mowing between rows ("debris" being anything up to 10cm thick, you just mow along the length a few times and then it's woodchips).