On March 24, 1999, about 0130 hours mountain standard time, an Ayres Corporation S2R-G10, N20523, ran off the end of the runway and collided with a berm during the takeoff roll at a private airstrip near Stanfield, Arizona. The airplane, operated by Crop First Aviation Inc., Stanfield, was substantially damaged. The commercial pilot sustained minor injuries. The local aerial application flight, conducted under the provisions of 14 CFR Part 137, was originating at the time of the accident. Night visual meteorological conditions prevailed and no flight plan was filed. The pilot reported that the purpose of the flight was to spray a cotton field with insecticide. The aircraft was loaded with approximately 430 gallons of chemicals and about 110 gallons of fuel. The pilot stated that he began the takeoff roll using the entire length of the 2,200-foot-long runway, and noted that the engine temperature gage reached the red line earlier than usual and he reduced the power somewhat to keep from exceeding limitations. He reported that the acceleration seemed sluggish, and the airplane overran the runway end and collided with a berm that rose about 6 to 8 feet above the runway surface. The airplane then jumped across a ditch, continued through an alfalfa field, and slid to a stop. The pilot reported that the airplane was becoming airborne right at the time of impact. Three ground crewmember/witnesses reported that they didn't notice any unusual noises from the engine, but they noted that it seemed like a "slow acceleration." The pilot reported that he had not experienced any mechanical problems with the aircraft or engine prior to the accident, and stated that the engine sounded normal during the takeoff roll. He further reported that the accident could have been prevented by taking off with a lighter load.