Brion,
   Your comments reminded me of another issue and that is soils that are wet natured -- fragipans and possibly tiled.  These soils need different management and more frequent liming.  I would expect them to be more problematic regarding pH than well drained soils when no-tilled.  I also find some of these soils to be less responsive to the benefits of no-till especially if the fragipan is less than 30 inches.