we've used the Auburn soil testing lab for years. our results from the AU lab were recently all over the map from comparable samples taken over the last 5 years. for fun this summer is sent the same 10 field soil samples to AU and LSU soil testing labs.... the LSU recommendations were much more consistent w fertilizer recommendations as compared to the actual K/P levels in each field. the field PH levels were consistent from both labs- with the AU PH levels ALWAYS lower.. now out of 10 fields- both AU and LSU had the identical top (or bottom) 3 fields that need K/potassium or P/phosphorous etc. but the AU numbers were just not consistent.. w/ respect to the actual lbs of recommended fert. i think AU needs to re-calibrate their equipment. my 2 cents.

note: from both labs it was consistently clear that our sandy soils are always higher in P but lower in K. soils with more clay are higher in K but lower in P.