On September 7, 2000, at 1000 Eastern Daylight Time, a Cessna 177RG, N2156Q, was substantially damaged while landing at a private airstrip in Elmer, New Jersey. The certificated flight instructor and the private pilot/owner, who was receiving a biennial flight review, were not injured. Visual meteorological conditions prevailed, and no flight plan was on file for the instructional flight conducted under 14 CFR Part 91. According to the instructor, on the day of the accident, the pilot wanted to take the airplane to Cross Keys, New Jersey, to have the transponder inspected, and then complete a biennial flight review. The airplane departed Elmer about 0800, and flew to Cross Keys. The transponder inspection was completed, and the two pilots boarded the airplane, taxied to Runway 06, and departed. While climbing out, the instructor, who was in the right seat, had the pilot don a hood. While heading in the general direction of Elmer, the pilot leveled the airplane at 1,500 feet msl, and the instructor had him execute some turns to a heading in both directions. The instructor then had the pilot remove the hood, and perform several slow-flight maneuvers. Once at Elmer, the airplane entered a left downwind at 1,500 feet msl for Runway 08, a 3,500-foot by 50-foot runway that was bordered by corn 3 feet from the edge on both sides. The instructor told the pilot to conduct a power-off landing. When the airplane was abeam the touchdown point, the pilot retarded the throttle, lowered the landing gear, and selected one notch of flaps. The instructor commented to the pilot, "I wouldn't have done that," but decided to let the pilot continue with the approach, because it appeared the pilot would still make the touchdown point. The pilot made one continuous turn from downwind to final. On the base leg portion of the turn, the pilot selected the second notch of flaps. He then turned final 1,000 to 1,500 feet from the touchdown point, and 350 to 400 feet agl. At some point on final, the pilot selected full flaps. While on final the instructor felt everything was going "ok," although the pilot's technique was a "little" different than his own. When the airplane was about 10 feet above the runway, the pilot commented they were going to hit a little hard. The instructor responded by telling the pilot to add "a little power." The pilot advanced the throttle to full open; the airplane turned left; the left wing contacted the corn; and the airplane impacted the ground. The airplane came to rest, and the instructor and pilot exited under their own power.