Pvafarm - 1/31/2026 19:22

Well OK, I'm nowhere near knowing how to variable rate N and I say that after 25 years of doing on-farm N trials. I've talked and posted in the past about the Nitrogen Optimization Pilot Program (NOPP) WI is legislatively funding through our Dept of Ag.  This program was developed by the ag community and our UW in response to draconian rules the DNR wanted to impose on WI farmers 5 years ago. I won't go into detail on this, however know that this has given the farm community the ability to fight the "I thinks" of regulators with science and data to show that we CAN be environmentally responsible with increased N rates AND maximize farmer profitability. In fact the MRTN rates for WI have been increased significantly this past winter due in part to all the data many of us have generated around the state. We are using scientifically defensible methods to prove what we are doing is right.

My current project was started 3 years ago on my own farm - 2 fields, 2 years, 1 being lower yielding sandy loam soil and 1 being high yielding loam/silty clay loam soil.  We had 2 polar opposite years with 2023 being very dry, 2024 was extremely wet so data was "interesting" and non-conclusive.  For 2025 I was able to add 4 more cooperators so we have 3 paired studies.  Good rains this year, got a bit dry early August and then 8"+ rain in 10 days saturated everything for awhile.  Below I posted page 1 that summarizes what the study is looking to do.  The second pic shows data from 2025.  Note in the colored boxes on the right that the High Yield fields yielded a bit less than the Low/Med Yield Soils.  It's not uncommon to see a 40-50 bpa yield advantage to the High Yield soils.  Not this year.

NOPP Trial Goal 1:  Add to the MRTN database from multiple sites.

NOPP Trial Goal 2:  Determine if soil type/texture/OM is useful when building Variable Rate N Recs.

My Ask of NAT:  Those of you that are building VR N Recs - what are the metrics you use to build out a final recommendation?