The airplane nosed over during an aborted takeoff in a pasture following a touch-and-go landing. The pilot had landed on the downhill grass-covered pasture to practice touch-and-go landings. The landing was uneventful. However, during the takeoff roll when the airplane approached the end of the field, the pilot decided to abort the takeoff. According to the pilot, his brake application was excessive and the airplane nosed over. No mechanical malfunctions were experienced with the airplane.