Prior to takeoff on the aerial application flight the pilot loaded applicant and fuel which, as reported by the pilot, put the airplane slightly over maximum gross weight. In addition, he checked the automated report for the nearest airplane weather facility, which reported wind from the north at four knots. The pilot departed the private strip, a 2,600 foot long turf and asphalt runway, to the south towards a river. While on takeoff roll, with a tailwind, the airplane was rotated for takeoff at the “normal” rotation point. The airplane climbed to about three feet then settled back to the runway. With a quarter of the runway remaining, the pilot continued the takeoff, increased flaps, and verified the throttle and propeller controls were full forward. The pilot again rotated the airplane and was able to climb about four feet when the airplane again settled back to the ground. The pilot then dumped the application load and tried to maintain control of the airplane. The airplane flew a short distance to the opposite river bank, impacted terrain, and slid on its belly. The pilot reported in preflight checks, the airplane had adequate oil and the fuel was sumped of any water. In addition, the pilot reported normal engine instrumentation prior to takeoff roll.