Catch it up if it needs it then just spread removal rates until sampled again, rinse, repeat.  I believe there's a bit of buildup in there rec's too.  We spread our own vrt.  Keep the combines accurate and use the yield maps and we have the co-op write the prescription, for now.  Eventually will get setup to make our own, sometimes it's just hard to get the time to do it when were harvesting and wanting to get out there and start spreading.