THE PILOT STATED THAT THE PURPOSE OF THE FLIGHT WAS TO OBSERVE CROP DEVELOPMENT. THE FLIGHT WAS CONDUCTED AT A LOW ALTITUDE. ALTHOUGH THE PILOT DOES NOT RECALL THE EXACT REASON FOR LOSS OF CONTROL OF THE AIRCRAFT, THE LAST THING HE REMEMBERS WAS MAKING A LEFT TURN. A WITNESS SAW THE AIRCRAFT DESCENDING WING AND NOSE DOWN INTO THE TERRAIN. THE AIRCRAFT WAS SUBSTANTIALLY DAMAGED AND THE PILOT SUSTAINED SERIOUS INJURIES. SUBSEQUENT INVESTIGATION REVEALED NOTHING OF A MECHANICAL NATURE THAT WOULD HAVE HAD A NEGATIVE IMPACT ON THE FLIGHT.