According to the pilot, the aerial application flight was one of several that day at the same aircraft weight, ambient temperature, and wind speed. Due to some variable winds, the pilot elected to takeoff in a different direction from the previous flights. Approximately 30 feet above ground level and above the tree line, the pilot felt the airplane begin to sink and he was unable to maintain altitude. He stated, "I believe there was a very small wind shear or wind shift just above the tree line and I had not yet achieved enough forward airspeed to overcome the loss in lift." The airplane impacted terrain and came to rest inverted. Examination of the airplane revealed the engine was separated from the airframe and the empennage was bent. No anomalies were noted with the airframe or engine that would have precluded normal operation. The accident day was the first time the pilot conducted aerial application flight activity.