The pilot attempted to takeoff from a private grass strip and struck standing corn at the departure end the runway causing the airplane to flip over and land inverted. The airplane sustained substantial damage. The pilot received only minor injuries. The airplane was loaded with 120 gallons of fungicide and between 1/2 to 3/4 fuel and no mechanical abnormalities were noted prior to the accident. Weight and balance calculations indicated that the airplane was within maximum gross weight and center of gravity limits for the conditions at takeoff. The pilot stated that he had a slight headwind but after a normal liftoff from the runway, he felt like he encountered either a wind shift or downdraft.