The pilot of the nose landing gear-equipped airplane was conducting glider tow operations, and after landing from the second tow, he was taxing to the opposite end of the airport in the grass next to the runway. The pilot further described that it was common practice to tow gliders for takeoff from the paved runway and to land in the opposite direction on the grass next to the runway. The pilot decided to cross an intersecting paved taxiway at a different place than he normally would, so he could be seen by the other tow aircraft. While attempting to cross the taxiway the nose landing gear contacted the taxiway edge, collapsed, and resulted in substantial damage to the fuselage. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.