The pilot was performing touch and go landings on runway 09 (3,451 feet by 50 feet, asphalt) when the airplane impacted terrain during takeoff. The pilot stated that during the last takeoff, the flaps were retracted and full throttle was applied. The ground roll seemed "slightly longer" than previous takeoffs. After liftoff, the airplane was not climbing and was developing less than full power. As the airplane was approaching power lines, the pilot felt that the airplane would not clear them so she elected to land on a field. The airplane impacted the ground during the landing and sustained substantial damage, which included a damaged left wing, a ruptured fuel tank, and a deformed fuselage. Examination of the airplane revealed that the airplane cockpit flap indicator was in the 20 degree position. No mechanical anomalies were noted with the airframe, engine, and engine accessories that would have precluded normal operation.