The pilot reported that the engine faltered briefly when he applied full power while rolling out of a procedure turn during an aerial seeding operation. He then deliberately stalled the aircraft into the tops of trees when it was clear that it was losing performance. The aircraft rolled right and struck the ground in a nose down, inverted attitude. The pilot and station manager occupied the front seats, the seed dispatcher was tethered by a lanyard in the rear cabin from which the seats had been removed. All three occupants were taken to hospital, two with minor and one with serious injuries. The aircraft carried an emergency locator transmitter (ELT) which was fixed to structure in the rear fuselage. The ELT worked automatically, alerting AusSAR to the accident. Onsite photographs indicated that the engine was producing high power when the propeller struck tree trunks. The flight conditions were extreme; 43 degrees C, moderate turbulence and a density altitude of approximately 5,200 ft.