THE PILOT OF THE AGRICULTURAL SPRAY PLANE WAS ATTEMPTING TO TAKEOFF FROM HIS ROUGH, TURF FARM STRIP. HE SAID HE FELT THE LEFT MAIN GEAR WHEEL 'DROP IN A RIDGE' DURING THE TAKEOFF ROLL, AND THAT THE SPRAY BOOM SUBSEQUENTLY CAUGHT IN THE WHEAT BORDERING THE RUNWAY. HE WAS UNABLE TO MAINTAIN DIRECTIONAL CONTROL, AND THE AIRPLANE WENT INTO THE WHEAT FIELD. NO PREIMPACT MECHANICAL PROBLEMS WITH THE AIRPLANE WERE CLAIMED OR DISCOVERED.