The airplane collided with rough terrain during a forced landing following a loss of engine power. The pilot reported that they were practicing touch and go landings when the engine power decreased by 100 to 150 rpm during takeoff. The pilot confirmed the boost pump position, the mixture setting, and the fuel quantity. He reported that at an altitude of about 500 feet above the ground the engine power decreased smoothly to zero. The pilot reported there were crop fields on both sides of his path with a slew in the middle so he elected to land straight ahead in the slew. The airplane touched down in the four-foot-tall grass at which time the nose and right main landing gears collapsed resulting in structural damage to the airplane. The fuel servo was removed from the airplane and bench tested. The test revealed the servo had a tendency to stick when transitioning between high and low pressure settings.