The private rated pilot conducted a local pleasure flight and returned to a private grass airfield. He reported that he had poles located at the end of the runway, to help establish the runways' s center line and that there was a field of standing corn on the left side of the runway. He added that during the landing he was slightly left of the runway centerline and should have executed a go-around. The airplane's left wingtip impacted the corn and the airplane continued left into the corn, nosed over, and came to rest inverted. Examination of the airplane revealed substantial damage to the fuselage and wings.