THE PILOT STATED HE WAS MAKING A LOW PASS (ABOUT 4 FEET ABOVE THE CROPS) FOR PURPOSE OF AERIAL APPLICATION WHEN 'THE ENGINE SURGED....' WHEN HE LOOKED DOWN TO TROUBLESHOOT THE PROBLEM HE TOOK HIS EYES OFF THE CROP. HE REPORTED 'THE NEXT THING I KNEW I WAS IN THE CORN, I PULLED BACK OUT OF IT, BUT THE INTAKE HAD INGESTED TOO MUCH CORN. THE ENGINE SEEMED LIKE IT WAS RUNNING ON 3 CYLINDERS...' THE AIRPLANE STRUCK A ROW OF CEDAR AND SETTLED INTO A CORN FIELD.