According to the delivery pilot of the recently-sold vintage military trainer, he first landed the airplane at a paved airport near the new owner's farm. The new owner then asked the pilot to fly the airplane to a dirt airstrip on the farm. The pilot subsequently went to the airstrip with the new owner, determined that it was acceptable, and later returned with the airplane. During the landing flare, the airplane floated from what the pilot later surmised were convective currents from the hot soil. It subsequently touched down long and overran the end of the 1,380-foot airstrip. During the overrun, the airplane encountered a soft spot in the adjoining onion field and nosed over, damaging the rudder and vertical fin. The landing direction was to the north, while the nearest recorded airport weather indicated that the winds were from the east at 5 knots. There were no preexisting mechanical anomalies noted with the airplane.