On March 7, 2002, at 1217 Pacific standard time, a Schweizer G-164B, N48631, veered off a dirt strip and overturned after landing near Dixon, California. The commercial pilot/owner was operating the airplane under the provisions of 14 CFR Part 137. The pilot, the sole occupant, was not injured; the airplane sustained substantial damage. The aerial application flight departed from the strip about 1200. Day visual meteorological conditions prevailed, and no flight plan had been filed. The incident was upgraded to an accident on April 4, 2002. The pilot stated he had completed several flights that morning from a primarily north-south dirt strip in the middle of a wheat field. He had been taking off and landing to the north with a quartering tailwind from the southwest. Gusty winds and showers had been passing through the area all morning and the strip had ruts and puddles. After his third turn, he landed to the south, but the airplane got stuck in a mud puddle, and his crew pulled the airplane out. On the next flight he elected to depart to the north. The pilot completed two more load cycles successfully by departing and landing to the north. On the accident landing, he placed the left main landing gear in the center of the strip and the right main landing gear near the edge of the strip, which was soft and wet. The wheel grabbed into the soft dirt, and the airplane veered to the right into the wheat field. The airplane overturned, which resulted in substantial damage to the wings and empennage.