On July 11, 1995, at 1140 central daylight time, an Air Tractor AT-401, N1004W, nosed over during a forced landing near Cash, Arkansas. The commercial pilot was not injured and the airplane sustained substantial damage. No flight plan was filed for the aerial application flight conducted by Morrison Aircraft Corporation under Title 14 CFR Part 137. Visual meteorological conditions prevailed for the flight which departed a private airstrip near Cash at 1135 CDT. According to the pilot, he was en route to fertilize a field when the engine lost power and began "backfiring, missing and smoking." The pilot dumped the load of Urea and attempted to return to the private airstrip. The engine continued to lose power and the pilot landed in a soybean field. The airplane nosed over and came to rest inverted. Damage included a bent vertical stabilizer and rudder and deformed rear fuselage longerons. The operator arranged to have a certified repair station examine the magnetos. When run on a test stand, one of the magnetos failed to spark. Disassembly revealed that an internal drive gear had failed. The other magneto was tested and failed to spark below 400 rpm and displayed "erratic misfiring" above 400 rpm. The point gap clearance was measured and found to be "too wide causing misfiring at low and high rpm."