The 325-hour private pilot stated in the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1), that while in cruise flight at 1,100 feet mean sea level (msl), he noted that the oil pressure had fallen below 20 pounds of pressure as he was returning back to his private airstrip. The pilot stated that he made the decision to prepare for an emergency landing and initiated a descent into a large wheat field that he deemed was best suited for an off-airport landing. The pilot added that while approaching the wheat field, "my motor started to flutter so I got down to the wheat field and that's when my tires got into the wheat and it flipped us over." Examination of the airplane by an Federal Aviation Administration (FAA) inspector, who responded to the accident site, revealed that the airplane left wing spar was bent, and the engine firewall was displaced. The inspector also noted that there were no wheel marks evident on the ground. The inspector added that the wheels of the tailwheel-equipped airplane were caught in the tall wheat, which caused the airplane to nose over. The reason for the reported loss of engine power could not be determined. At the time of the accident, the weather was reported as wind from 360 degrees at 13 knots, gusting to 17 knots, 10 statute miles visibility, clear skies, with a temperature of 79 degrees Fahrenheit, dew point of 48 degrees Fahrenheit and an altimeter setting of 30.01 inches of Mercury.