Dunn County Extension outlines nitrogen-management results and previews Healthy Water Summit

Jerry Clark, soils and crops educator with Dunn County Extension, presented a series of on‑farm and pilot‑scale studies to the Community Resources and Tourism Committee on March 17, summarizing findings on nitrogen management, manure crediting and nitrate movement ahead of a regional Healthy Water Summit.

The presentation framed agriculture’s local scale: Clark said agriculture accounts for nearly $400 million in market value in Dunn County, with product sales just over $300 million and roughly 1,200 farms reported in the 2022 Census of Agriculture. He then reviewed results from small‑plot adaptive nitrogen trials and a Nitrogen Optimization Pilot (NOP) conducted across the region.

Clark described small‑plot trials that tested seven nitrogen rates (0–200 lb/acre). "In 2025, once we got to about 40 pounds of nitrogen, it didn't pay to put any more on after that," he said, adding that in that field extra nitrogen above that level would be "basically throwing money away." By contrast, a 2024 plot showed a higher agronomic optimum (about 143 bushels per acre) and an economic nitrogen rate closer to 127 lb/acre once fertilizer cost was considered.

At field scale, the NOP project found manure supplied a substantial nitrogen credit in 2025. Clark showed that with manure applied the economic nitrogen rate was near 55 lb/acre, while without manure it was near 158 lb/acre — roughly a 100‑lb nitrogen credit from manure in those trial strips. Clark framed that result as evidence that accounting for manure value in fertilizer decisions can reduce commercial nitrogen use while holding yields.

To measure nitrate movement, the team installed dozens of small lysimeters across replicated treatments. Clark said most lysimeter readings clustered as expected but flagged eight high outliers; six of those high readings corresponded with locations where a subsurface tile line runs through the field. Clark cautioned that tile lines can move more water (and dissolved nitrate) through specific field zones, a pattern UW–Madison researcher Steven Hall will review at the upcoming summit.

Clark also described hands‑on training innovations used in manure‑applicator workshops: participants worked with a tabletop mapping exercise (including 3D‑printed models of equipment) to simulate safe truck placement, hose routing, stream crossings and other operational decisions. He said the mapping exercise expanded discussion and improved participant engagement compared with slide‑only sessions.

The extension presentation concluded with logistics for the Healthy Water Summit — scheduled for Friday at Chippewa Valley Technical College’s West Campus (registration 8:30 a.m.; program roughly 9 a.m.–3:30 p.m.; $20, with CCA credits available). Clark said speakers will include UW–Madison researchers and regional experts on pesticide residues, nitrate movement and sediment. "We're pulling partners together across the three counties because water doesn't just stop at county lines," he said.

During Q&A, Clark explained common causes of yellowing or burned‑looking corn — including soil type, heavy ponding for more than 72 hours (which can cause nitrogen loss or suffocation), timing of granular fertilizer applications and volatilization — and answered questions about how extension and county land‑and‑water conservation staff coordinate research, monitoring and outreach.

Next steps: the committee was encouraged to attend the Healthy Water Summit and to share follow‑up questions with extension staff. UW–Madison researcher Steven Hall is scheduled to present additional lysimeter findings at the summit, and extension staff said they will continue to analyze field data to refine management recommendations.

Notes: all quoted attributions are to speakers recorded in the committee meeting transcript; specific numeric results come from Clark’s presentation slides and handouts referenced during the meeting.