On August 14, 2002, at 0850 central daylight time, a Piper PA-25-235, N7634Z, sustained substantial damage when the airplane stalled during takeoff and impacted the terrain in a wheat field near Ray, North Dakota. The commercial pilot was not injured. The 14 CFR Part 137 aerial application flight was departing from a private grass airstrip on a local flight. Visual meteorological conditions prevailed. No flight plan was filed. The pilot reported he had returned to the airstrip in order to fix a plugged spray nozzle. He landed on the southwest runway of the grass airstrip. Once the nozzle was fixed he departed to the northeast. He reported he departed on the northeast runway due to a construction crane located at the southwest end of the runway. He estimated he departed with a 3-4 knot tailwind. He reported, "Upon liftoff, enough airspeed was not obtained to be able to clear the tree row. Once out of ground effect, a stall occurred which may have come from a downdraft + or the possibility of a spark plug fowling while idling to fix nozzle." He reported, "Upon realizing the stall, power was pulled back + had to land in grain field."