The solo student pilot reported that, while practicing a soft field takeoff, he applied full power and pitched the nose of the airplane to "above the horizon." The airplane became airborne, the wind drifted the airplane to the left, and the airplane struck a hay bale on the left side of the runway. The student turned the airplane toward the runway and landed on the remaining runway without further incident. The airplane sustained substantial damage to the fuselage and empennage. The chief flight instructor reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The airport's automated weather observation station reported that, about 34 minutes before the accident, the wind was from 240° at 4 knots. The same automated station reported that, about 26 minutes after the accident, the wind was from 240° at 9 knots. The student pilot was departing runway 17. The chief flight instructor reported that the student pilot's flight instructor told him to not practice soft field takeoffs during a solo flight. The instructor stated that the student required more practice on the takeoff technique.