On March 23, 1998, at 1145 central standard time, an Air Tractor AT-401, N1524H, operated by Baker Flying, was substantially damaged. During landing rollout on a taxiway that was customarily used by aerial applicator pilots for landings, the airplane struck a pile of gravel that had been dumped on the taxiway. The commercial pilot was not injured. The CFR Part 137 flight had departed an airstrip near Caruthersville, Missouri, on a local flight, but diverted to the Steele Municipal Airport, Steele, Missouri, due to rain showers in the area. Visual meteorological conditions prevailed and no flight plan had been filed. The pilot reported that it was his first flight to the Steele Municipal Airport during the new spraying season. He reported the airport was used primarily by aerial applicator pilots. He reported the customary practice at the airport during the spraying season was for the airplanes to land on the taxiway and takeoff on the runway. He reported that he made a straight-in approach to the runway from the south. He landed on the taxiway and during the landing roll-out, the airplane hit a pile of gravel that had been dumped in the center of the taxiway, midway from the approach and departure ends of the taxiway. The pilot reported that he did not see the gravel because its color blended in with the color of the taxiway. The pilot reported that if he had made a standard downwind entry into the traffic pattern, he would have most probably seen the piles of gravel on the taxiway. The airport manager reported the gravel had been dumped on the taxiway for airport reconstruction that was in progress. The manager reported that there had not been much traffic at the airport recently. He reported that a NOTAM had not been issued for the closed taxiway. The airport manager reported that the runway was closed at night since the runway lights were disconnected due to the construction. No NOTAM had been issued for the runway closing at night.