Luke, I see a fair amount of stuff that looks very similar.   One thing I believe to be in play, in the fun little area from where you live to where I live, is the extreme swings we have been seeing from periods of saturation to periods of drought.   It hasn't been helpful for natural mineralization and bacterial activity in the soil.    

There are portions of some of my fields which have been problem areas because of drainage my whole life which I have recently pattern tiled.  They have poor P/K  levels compared to other parts of the same fields which were not perennial mudholes, even though for years and years before GPS they were getting blanket applications of the same dry fertilizer or manure.   It's not because more bushels were leaving those areas in a combine.   I have a hard time drawing any conclusion except that being suffocated by excess water is different from soil that can breathe.   It's going to be interesting to see how those acres react to a few growing seasons of both having a consistent stand of crop that yields and having some targeted fertilizer.