It is naturally subirrigated, no pipes at all.  Depending on rain and location the water table is 2-6feet below ground.  Even the severe drought we had last year the grass still grew well.  I don't know how practical it is spreading $50-60 an acre of fertilizer with our carrying capacity.  Carrying capacity on the poor soil is 8 acres/pair.  The subirrigated ground when it isn't hayed is somewhere around 3 acres/pair, so maybe fertilizer would be cost effective there if we could roughly double the capacity.  It looks like getting soil tests done is the best path as long as it isn't too late to fertilize after the big rain we had.