The pilot reported that the airplane became airborne about 2/3 of the way down the runway during an attempted soft field takeoff from a dirt runway. He said he was unable to maintain an adequate airspeed and drifted off to the left side of the runway and impacted bushes and shrubs. During the accident sequence, the front landing gear folded back, and the left main landing gear broke off. The outboard half of the right wing was partially separated.