The student pilot was flying a solo navigation exercise from Headcorn to North Weald. With a forecast wind speed of 10 kt and in good visibility, the pilot made an approach to land on asphalt Runway 20. The aircraft bounced on the first touchdown and then landed heavily with a slight yaw to the right. The pilot stated that, at that point, the aircraft appeared to be caught by a gust of wind which tipped the aircraft onto its side and it departed the right side of the runway and came to rest on the adjacent grass Runway 20. The pilot was unhurt and he turned off the engine before stepping out of the aircraft. He later attributed the cause to having rounded out too early during the landing.