The pilot stated that while on takeoff from a 2,200 ft partial concrete and grass private runway, the airplane failed to lift off due to density altitude. He initiated a controlled dump of the hopper load near the end of the runway to increase climb performance. The pilot stated that the airplane then stalled and impacted terrain off the departure end of the private strip, which resulted in substantial damage to both wings, fuselage, and empennage. The pilot reported that there were no preaccident mechanical malfunctions or failures that would have precluded normal operations. The accident occurred after the pilot had conducted several agricultural spray applications with 350 gallon loads. He stated that temperature had reached 96°F and he should have carried a smaller load since conditions were not favorable. At the time of the accident density altitude had increased to about 2,530 ft.