On June 20, 2003, at 0940 eastern daylight time, an Air Tractor AT-301, N3659T, operated by Robertson Crop Dusting Service Inc., sustained substantial damage during a forced landing 7 miles south of South Haven Area Regional Airport (0D1), South Haven, Michigan. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 137 aerial application flight was not operating on a flight plan. The pilot reported minor injuries. The local flight departed 0D1 at 0840. The pilot stated he was returning to 0D1 after the local flight when the engine backfired twice. He reported that he landed in a field, however, the terrain was sandy and rough. The aircraft subsequently nosed over prior to coming to rest. The pilot stated that the aircraft had been fueled with approximately 100 gallons one or two flights prior to the accident flight. The aircraft's normal fuel consumption was about 35 gallons/hour, according to the pilot. He estimated the total flight time since refueling had been 2-1/2 to 3 hours. Approximately four gallons of fuel were recovered from the aircraft after the accident. The aircraft's type certificate data sheet lists a maximum fuel capacity of 126 gallons with 120 gallons useable. The pilot reported no malfunctions with the airplane prior to the loss of engine power. A post-accident examination of the aircraft and engine did not reveal any pre-impact anomolies. No evidence of fuel contamination was present. The pilot stated that the "most probable cause [of the accident was a] lack of fuel."