The 5,149-hour commercial pilot reported that his first flight of the day had been delayed due to thunderstorms moving through the area. The pilot added that as the agricultural airplane reached 50-60 mph during the takeoff roll, the tailwheel became airborne as the pilot encountered a gusting crosswind from the right requiring full right rudder and brakes. The pilot was not able to compensate for the existing conditions and the airplane departed the left side of the 4,120-foot long Runway 26. As the airplane exited the 20-foot wide runway, the 5,149-hour pilot retarded the engine power and dumped the 150-pounds load of agricultural mixture. About the same time, the right landing gear tire sank into the soft ground to the left of the runway and the airplane nosed-over. The airplane came to rest in the inverted position and the pilot was able to egress from the single-engine airplane without injuries. Both wings separated from the airframe during the accident sequence. Weather at the airport was reported as winds from 085 degrees at 2 to 5 knots, visibility 10 statute miles, with scattered clouds at 1,500 feet and an overcast ceiling at 5,200 feet, a temperature of 20 degrees Celsius, a dew point of 16 degrees Celsius, and an altimeter setting of 30.14 inches of Mercury. The pilot added that there were thunderstorms in the area at the time of the mishap.