The pilot had just commenced a procedure turn at the end of a spray run, at a height of 200 feet above ground level, when the engine failed without warning. During the ensuing forced landing the aircraft landed heavily and overturned. The engine failure was caused by separation of number nine cylinder link rod end, which resulted in the piston lifting the head off the cylinder. The cause of the failure could not be positively determined, but was probably due to the link pin bush being worn away, and excessive tolerance between the link rod and link pin causing a fatigue failure of the link rod. Aircraft records showed that the engine had completed 184 hours since overhaul, but the internal appearance of the engine was that of an engine that had operated for a longer time. The reason for the unusual condition of the engine could not be established.