Center pivot irrigation system

The method of irrigating a circular area with a reversible center pivot irrigation system wherein an obstruction is in the path of the outer end of the center pivot irrigation system is disclosed. In one embodiment, the last drive unit and the pipe span supported thereon may be moved to a trailing position with respect to the next to last drive unit to avoid the obstruction. In another embodiment, the last drive unit and the next to last drive unit and the pipe spans supported thereon may be moved to a trailing position with respect to the second to last drive unit to avoid the obstruction.