The airplane was substantially damaged when it departed the paved runway surface and then struck a ditch. The nose landing was torn from the airplane resulting in damage to the firewall and forward fuselage. The student pilot reported that the accident flight was his first solo flight without an instructor pilot on-board. Immediately prior to the accident flight the student and his instructor had performed a flight which included landing practice. Subsequent to this flight, the instructor pilot endorsed the student pilot's logbook authorizing the solo flight. The student pilot reported that he then took off and flew a traffic pattern approach to landing. After touchdown, the student pilot inadvertently added power to execute a touch and go rather than the full stop landing. Upon realizing that he was to execute a full stop landing, the student pilot reduced power and applied the brakes. He reported that the nose wheel began to shimmy and he applied the brakes harder. The airplane subsequently went off the side of the runway into the grass and then struck a ditch before coming to a stop.