On June 20, 2000, approximately 1835 mountain daylight time, a Stinson 108-1, N8865K, experienced a gear collapse during a precautionary landing just after takeoff from Mountain Home Municipal Airport, Mountain Home, Idaho. The private pilot received minor injuries, but his passenger was not injured. The aircraft, which was owned and operated by the pilot, sustained substantial damage. The flight, which was in the process of departing for Evergreen field, Vancouver, Washington, was being operated in visual meteorological conditions. No flight plan had been filed. The ELT, which was activated during the accident sequence, was turned off at the scene. The pilot, who had not calculated takeoff performance data prior to the attempted departure, was departing in strong, gusty winds, with a temperature of 78 degrees Fahrenheit. When the aircraft reached about 75 feet above the ground, it encountered moderate turbulence and sinking air. Because it appeared that the aircraft might not out-climb the unfavorable terrain along the planned departure route, the pilot elected to make a precautionary landing in an open field. He reported that the touchdown was successful, but during the landing roll, one of the main gear encountered rough/uneven terrain and folded over. Based on a field elevation of 3,164 feet, a temperature of 78 degrees Fahrenheit, and a barometric pressure of 30.05 inches of Mercury, the density altitude at the time of departure was approximately 5,100 feet.