I covered all or parts of 11 counties in the seed business.  I had a core of 3 counties and the company played around with the rest of my territory. (that is another subject I don't want to digress into).  In my 3 core counties, only one had a plot I would trust, and its results never matched what I saw on my farm.  THAT was probably due to different soil types and operating philosophy.

Besides the one I mentioned earlier, another one kind of soured me.  The county extension put on a joint plot with the Soil Conservation Service .... on the side of a hill they had constructed terraces on!  Absolutley worthless data.

That was when I started questioning extension advisors about how they conducted plots and discovered most either didn't have a clue or just didn't bother.