The pilot returned for landing in the tailwheel configured airplane after an agricultural application flight. He executed a normal landing on runway 12 (2,230 feet by 200 feet, asphalt/turf) and kept the tail up as long as possible as the airplane slowed. The pilot stated that when the tailwheel touched down it felt as if the tail was dragging on the ground and the airplane drifted to the right. He applied opposite rudder but was unable to stop the drift. He subsequently applied the brakes, which spun the airplane around and brought it to a stop partially off the runway. The pilot reported that after the accident he observed a bolt securing the tailwheel had failed. The bolt was discarded and was not available for further examination. The pilot commented that he will proactively inspect and replace the tailwheel bolts before each spray season.