The pilot was conducting spreading operations on a flat paddock, but about 800 metres from one boundary the ground rose sharply by about 200 feet. At the end of a run towards the rising ground a procedure turn was commenced. During the turn, the pilot realised that the aircraft was closer to the rising ground than intended. Despite corrective measures, the pilot was unable to prevent a collision with a tree. The aircraft then struck the ground and came to rest in a further clump of trees. Weather conditions at the time of the accident were overcast, with rain showers and a strong gusty wind. On the runs towards the rising terrain the aircraft was subjected to a substantial tailwind component and possible downdrafts. As the pilot commenced a procedure turn at the end of the last run, the aircraft had drifted further downwind than expected, leaving insufficient margin to complete the turn safely.