On July 23, 2011, about 0930 central daylight time, a Cessna A188B, N9234R, experienced a total loss of engine power while maneuvering over a field near Mount Hamill, Iowa. The pilot subsequently made a forced landing to a field. The commercial pilot was uninjured. The airplane sustained substantial damage to the airframe. The airplane was registered to and operated by Air Advantage Inc under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed and a flight plan had not been filed for the local flight that departed from Mount Pleasant Municipal Airport (MPZ), Mount Pleasant, Iowa, about 0840. The pilot stated that he was lining up the airplane for the last spray pass of a corn field when he noticed that everything was getting quiet and the controls were less responsive. He looked and the gauges and noticed the airspeed and fuel pressure were low. He then turned to fly away from the corn field and turned on the emergency boost pump. He then performed a forced landing to a soybean field located south of the corn field. During the landing, the left wing struck the ground upon touchdown which was then followed by the right wing contacting the ground. The airplane then nosed over and skidded on its nose until it came to rest on its landing gear. Examination of the airplane by a Federal Aviation Administration inspector revealed that the right fuel tank was empty, and the left fuel tank was almost 1/2 full. The inspector stated that the make and model of airplane does not have a fuel system check valve to prevent fuel migration from the opposite wing tank and/or header tank during turns.