The pilot of the Piper PA-28-235, was on final approach to land on a 1,640-foot-long, 50-foot-wide, turf runway, at a private airport. The pilot stated that he encountered a downdraft, which caused the airplane to settle into a cornfield, 30 feet prior to the runway threshold. The airplane sustained substantial damage to the firewall, fuselage, and both wings. The pilot reported that the wind at the time of the accident was from 260 degrees, at 1 knot, with no gusts. He further reported 370 hours of total flight experience, which included 32 hours in the same make and model as the accident airplane.