What happened
While taxiing for departure, the pilot noted to a passenger that the runway surface felt soft. The runway consisted of grass that was eight inches high.
During the takeoff roll, the pilot experienced slow acceleration. The aircraft reached a speed of 55 mph, at which point the pilot extended full flaps after having used 75 percent of the available runway length. As the aircraft climbed to an altitude of 25 feet, it encountered a downdraft. Because the airplane failed to climb further, the pilot elected to perform a precautionary landing.
During the landing sequence, the nosewheel of the aircraft struck a combined rut. This impact caused the airplane to nose over while traveling through grass that was three feet high. The occupants were not injured.