On June 12, 2013, at 0938 central daylight time, a Rockwell S2R agricultural airplane, N2249U, registered to Farmer Aerial AG LLC of Boise City, Oklahoma, sustained substantial damage during a forced landing after a loss of engine power near the Boise City Airport (17K), Boise City, Oklahoma. The commercial pilot was not injured. The aerial application flight was being conducted under the provisions of Federal Code of Regulations Part 137. Visual meteorological conditions prevailed and no flight plan was filed. The flight originated at 0915 from the Boise City Airport. The pilot reported that the intent of the flight was to apply pesticides to a field about 5 miles south of 17K. The takeoff and transit to the work area was normal, however, several minutes after a few spray runs, engine power began to degrade. The pilot decided to fly the airplane back to the airport. The engine power continued to degrade so the pilot switched the fuel boost pump switch to the "ON" position. The engine then completely stopped producing power and the pilot was forced to land the airplane in a corn field about 3 miles from the airport. During the forced landing, the left main landing gear collapsed and the airplane ground looped resulting in substantial damage to the fuselage and wings. After the airplane came to rest, the pilot exited the airplane without injury. The operator examined the fuel system and the engine following the accident. No anomalies were found to explain the loss of engine power.