On June 10, 1994, at about 1100 eastern daylight time, a Cessna 140, N89972 was substantially damaged following a nose over during an emergency landing near Bainbridge, Georgia. The commercial/instructor pilot received serious injuries, and the student pilot was not injured in the accident. The aircraft was being operated under 14 CFR Part 91 by Harrell's Aviation Services, Incorporated of Bainbridge, Georgia. Visual meteorological conditions existed at the time, and no flight plan had been filed for the local agricultural training flight. The pilot stated that while practicing agricultural spraying with a student, the aircraft engine revolutions per minute reduced to less than that required to maintain flight. An emergency landing was accomplished to a field, and during the roll out the aircraft nosed over in the soft terrain. Examination of the aircraft engine by the local maintenance facility did not reveal any reason for the aircraft engine loss of power.