The pilot was carrying out a spray run near the edge of a cotton crop. He was aware of a powerline crossing his intended flight path and had originally intended to fly over the powerline. At the commencement of the spray run he sighted the pole from which the wires were suspended. The pole was close to the edge of the crop, and assessing that there would be adequate clearance, the pilot decided to fly beneath the wires. However, as he neared the wires he lost sight of them due to poor background. The pilot descended the aircraft as close to the crop as possible in an attempt to sight the wires, and to gain maximum possible clearance. The wheels entered the crop and caused the aircraft to decelerate. The pilot was unable to prevent the aircraft from settling into the crop. The aircraft came to rest after tipping onto its nose and ground looping.