A pre-flight inspection of the airplane before an aerial application flight revealed the airplane's fuel tank quantity was 3/4 full of fuel. Two aerial application flights lasted approximately one hour. The aircraft was loaded a third time. The loader inquired if the aircraft needed fuel. The pilot checked the fuel gauge and informed the loader that there was slightly less than 1/2 tank. He said that the airplane would require fuel on the next load. The aircraft departed and flew for approximately 10 minutes. The engine stopped producing power, the pilot jettisoned the load, and he performed a forced landing on an adjacent field. The airplane nosed over and sustained substantial wing, fuselage, and empennage damage. No fuel was found on-scene in the airplane's fuel tanks or under the inverted airplane. Fuel was added to the fuel tank and the engine operated. According to the Federal Aviation Administration publication, The Pilot's Handbook of Aeronautical Knowledge, "aircraft certification rules require accuracy in fuel gauges only when they read 'empty.' Any reading other than 'empty' should be verified. Do not depend solely on the accuracy of the fuel quantity gauges."