The 15,000-hour commercial pilot reported in a telephone interview that he departed a timber tract with 15 gallons of fuel on-board en route to another tract located about 13 miles away. When the turbine-powered helicopter was approximately three miles short of his destination, while at an altitude of 600 feet above ground level (AGL), the engine lost power. The pilot entered an autorotation for a forced landing to an open field. Examination of the aerial application helicopter at the accident site revealed that no fuel was found in the fuel nozzle and less than three gallons of fuel was found in the fuel tanks. The turbine engine was removed from the helicopter and shipped to the factory for a detailed examination and test run. A written statement provided by the supervising FAA inspector, who witnessed the engine examination and test run, stated that the engine started and ran for an hour and twenty minutes with no discrepancies noted.