On August 2, 1995, at 1209 central daylight time, a Grumman G- 164A, N526Y, was substantially damaged following a loss of control near Searcy, Arkansas. The commercial pilot sustained serious injuries. The aircraft was being operated as an aerial application flight by Air Crop, Inc., under 14 CFR Part 137 when the accident occurred. Visual meteorological conditions prevailed for the aerial application flight for which no flight plan was filed. According to the operator, the airplane was topped off with 1,350 pounds of chemicals prior to departure from the airstrip. The pilot told the operator that the engine "didn't sound right" and elected to return to the airstrip. The airplane was observed climbing to approximately 300 feet AGL and entering the downwind leg. The operator added that during the turn from downwind to base leg "the airplane stalled and fell about 30 feet to the ground". The airplane impacted in a bean field, and nosed over coming to rest in the inverted position.