The student pilot of the Schweizer SGS 2-33A glider departed from the airport under tow, and released from the towrope at an altitude of 3,000 feet. He then maneuvered the glider to the right and flew around the airport "looking for lift." Over the next 30 minutes, the glider's altitude varied between 1,700 feet and 2,800 feet. When the glider started to lose lift, the pilot decided to return to the airport. The glider continued to lose lift and the student pilot entered the traffic pattern on the crosswind leg. As the student pilot turned onto final, he maneuvered the glider left of the runway centerline to avoid activity on the right side of the runway. While maneuvering, he "overreacted" and turned too far to the left and ended up over a cornfield. He attempted to turn back to the runway, but was "too low and slow." The glider impacted the cornfield, substantially damaging the fuselage. The student pilot reported 13 total hours of flight experience, 1 of which was in make and model. He also reported no mechanical anomalies with the glider.