On July 13, 2006, approximately 0940 central daylight time, an Air Tractor AT-301 single-engine agricultural airplane, N4422S, sustained substantial damage during a forced landing following a partial loss of engine power during initial take-off climb near Holcomb, Kansas. The commercial pilot, who was the sole occupant, was not injured. The airplane was registered to and operated by a private individual. Visual meteorological conditions prevailed, and a flight plan was not filed for the Title 14 Code of Federal Regulations Part 137 aerial application flight. The flight was originating at the time of the accident. According to the pilot, prior to departure from the private asphalt airstrip, the airplane contained 50 gallons of fuel and 150 gallons of chemical. Approximately 70 feet above ground level (agl) during initial takeoff climb, the engine "started to miss and backfire, causing a loss of climb power." Due to power lines in the airplane's flight path, the pilot reduced throttle, extended full flaps, and initiated a forced landing to a field. During the forced landing, the airplane "landed fast," and impacted soft, rolling terrain. Examination of the airplane by a local mechanic revealed the fuselage was bent and the main landing gear crushed aft. The magnetos were functionally tested with no anomalies noted, and mechanical continuity throughout the engine was confirmed. The reason for the partial loss of engine power was not determined.