On August 29, 1997, about 1330 eastern daylight time, a Air Tractor AT-301, N7307C, lost engine power and executed a forced landing into a field near Clewiston, Florida. The airplane was operated by Story Aviation, Inc. under the provisions of Title 14 CFR Part 137, and visual flight rules. Visual meteorological conditions prevailed at the time of the accident. No flight plan was filed for this aerial application flight. The commercial pilot was not injured, and the airplane was substantially damaged. The local flight originated from a private strip in Clewiston, Florida about 1330. According to the pilot, he was spraying a field with fertilizer when the aircraft's engine started shaking. He stated it quickly became worse until he did not have enough power to maintain altitude. He dumped his load of fertilizer and attempted to land in an open field. After touchdown, the airplane's wheels sank into the soft field, and the airplane nosed over. According to a FAA inspector, the #8 cylinder head had cracked through the spark plug hole. This led to a loss of engine power.