THE PILOT EXPERIENCED A TOTAL POWER LOSS WHILE EN ROUTE DURING AN AERIAL APPLICATION FLIGHT. HE SUBSEQUENTLY LANDED IN A WHEAT FIELD. DURING THE ROLL OUT, THE AIRPLANE ENCOUNTERED A RISE IN THE TERRAIN AND BOTH MAIN LANDING GEAR WHEELS SEPARATED FROM THE STRUTS. EXAMINATION OF THE ENGINE REVEALED A BROKEN CRANKSHAFT. EXAMINATION OF THE LANDING GEAR REVEALED CORROSION ON THE INSIDE WALLS OF THE STRUTS AND EVIDENCE OF PRE-EXISTING CRACKS.