On April 10, 1999, at 0755 central daylight time, a Piper PA-28- 140, N5416S, operated by Horizon Aviation, Mora, Minnesota, collided with trees following a loss of control while taking off from the Mora Municipal Airport. The student pilot received minor injuries. The airplane was substantially damaged. The 14 CFR Part 91 solo instructional flight was operating in visual meteorological conditions without a flight plan. The local flight originated at the Mora Muncipal Airport shortly before the accident occurred. The student pilot reported that he had practiced four short field takeoffs on runway 35 (3,998' x 75', paved) just prior to the accident takeoff. He then decided to practice a soft field takeoff. He stated he is 99% sure that he applied 20 degrees of flaps for the takeoff. He then held the yoke back and applied full power. He reported he felt the nose lifting and he "...failed to keep it from going too high and felt the back end raise." He stated the airplane got out of ground effect without enough airspeed to remain airborne. He reported he held the airplane "...steady but I was losing altitude and heading towards a tree line to my left side." The airplane contacted trees in a wooded area off the left side of the runway. The student reported the local winds were from 010 degrees at 10 knots gusting to 15 knots.