The pilot departed with the intention of performing a practice flight in the local area. After departing to the south and climbing to 2,500 feet, he noted that it was a little bumpy. He decided to fly to a grass strip, and practice landings. It still seemed bumpy at 2,500 feet, but he noticed that the American flag on the strip indicated no wind. He completed one uneventful touch-and-go landing; he touched down on the main landing gear with no bounce. After letting the tail wheel touch down and letting the airplane slow a bit, he applied power and took off. On downwind, the flag indicated a variable wind that was less than 5 knots. The second touchdown was soft with no bounce like the first one, and the airplane tracked straight down the runway. If the pilot detected any difference in the two landings, it was that speed on the second might have been slightly faster than the first one, and the airplane was in a more level attitude. He applied brakes, and the airplane nosed over. The pilot stated that there were no mechanical malfunctions with the airframe or engine. In hindsight, the pilot felt that the airplane would not have nosed over if he had applied less brake pressure.