On June 6, 2010, approximately 0930 central daylight time, a Piper PA-28R-180, N7559J, registered to and operated by the pilot, was substantially damaged when the nose landing gear collapsed on landing at Kingfisher Airport (F92), Kingfisher, Oklahoma. Visual meteorological conditions VMC) prevailed at the time of the accident. The personal flight was being conducted under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91 without a flight plan. The pilot and passenger on board the airplane were not injured. The local flight originated approximately 0915 from F92. The following is based on the pilot's accident report and what he told FAA inspectors. The pilot said this was his second landing on the grass strip that day. The winds were gusty and there was a slight crosswind. He turned onto final approach at 80 KIAS (knots indicated airspeed) with the landing gear down and flaps fully extended. He descended to the round out (flare), but the airplane "floated." He lowered the nose to allow the airplane to settle and he heard the stall warning horn intermittently. He applied full throttle and the engine responded but the airplane continued to descend. The airplane landed "hard." The left wing struck the ground, the airplane bounced, and then the right wing struck the ground. The nose gear collapsed and the airplane skidded to a stop. The pilot said he didn't take into consideration the density altitude when he prepared for his second landing. He said if he had maintained a higher landing speed, the airplane would not have stalled. An examination of the airplane revealed no anomalies.