Value of Frequent Soil Testing

I attended the Brownstown Agronomy Field Day put on by the University of Illinois today.  Presentations were interesting, but as always, I find myself looking at the same research results as the researchers and arriving at differing conclusions.  Fabian Fernandez made a presentation on potential changes to crop removal tables in the near future.  He has lots of compelling evidence and I have no problem with changing the tables as I have little use in their value anyway.  Nothing beats well done and frequent soil testing to determine soil fertility requirements.  The chart he presented below seems to be compelling evidence for frequent soil testing.  The research was done on a field where no fertilizer was added over a good number of years.  The dark dots show the predicted soil test levels based on crop removal.  The light colored dots show the actual soil test levels each year.  Fernandez believes that because the trend line follows in the same direction as the predicted line that we can get by with soil tests every 4 years.  My point would be that basing fertility recommendations on a soil test that fluctuates so much from removal and using the same test for four years could easily lead you in the wrong direction and have you  over applying or under applying for a long time.  Yearly testing is relatively inexpensive compared to the cost of over or under applying for 4 years.

As always click on the photo to enlarge it.