A multi-year Agriculture and Agri-Food Canada (AAFC) project is running field trials at five Western Canadian sites from 2023 through the 2027 growing season to quantify how soil moisture governs nitrogen losses.

The data will feed a grower-facing decision-support platform that rates fertilizer application windows by risk.

The work, led by AAFC research scientist Ramona Mohr at Brandon, Man., compares conventional urea with SUPERU, an enhanced-efficiency fertilizer containing both a urease inhibitor and a nitrification inhibitor.

Trials at Arborg and Brandon in Manitoba, Melfort and Swift Current in Saskatchewan, and Lacombe in Alberta test four application timings — early fall, mid-fall, late fall and spring — at multiple nitrogen rates.

Why does soil moisture matter so much?

Fall nitrogen remains common across the Prairies because autumn fertilizer prices typically undercut spring pricing. A single autumn pass also eases the seeding crunch.

The trade-off sits below the soil surface. Once applied, urea converts to nitrate, the form of nitrogen most vulnerable to loss. Under saturated soils, denitrification releases nitrogen as a gas. On lighter-textured ground, nitrate leaches below the root zone. Both pathways drain the fertilizer investment before the crop ever takes it up.

"The efficacy of different nitrogen management practices and the potential for loss of nitrogen can be strongly affected by soil moisture," Mohr said. "The difficulty that we have, though, is that our current technologies aren't really very good at predicting what soil moisture is going to be in the longer term."

That forecasting gap — predicting moisture weeks or months ahead at a specific site — is the project's central problem.

What are the trials actually measuring?

The field component tracks three variables: timing, source and rate. Researchers log fall and spring applications, conventional urea versus SUPERU, and several nitrogen rates per site.

The controlled-environment component sits at the intersection of moisture and temperature. Researchers expose urea to four soil moisture levels — relatively dry through to wet — at 5 °C, 10 °C and 15 °C.

The aim is to pin down how each combination accelerates or delays the urea-to-nitrate shift. Cooler soils slow the conversion. Inhibitor products extend that delay further. Mohr noted inhibitors "can also slow that transformation to nitrate, and that can help reduce the potential for nitrogen losses."

Early controlled-environment observations match long-established nitrogen science: wetter conditions speed conversion.

"With the higher moisture levels, there was more nitrate available and it moved farther away from the band," Mohr said. "The transformation of nitrogen is more rapid in that case, and so the movement out from the band is more rapid."

How will the decision tool work?

The team plans to fold five data streams into a single grower interface:

• Field trial results from the five Prairie sites
• Controlled-environment transformation and movement data
• Previously published nitrogen research
• Historical weather records
• Long-term soil temperature and moisture data

"The aim of that decision support tool is to give farmers local, area-specific information as to the relative safety or risk of different fertilizer application windows based on soil moisture conditions," Mohr said.

Who is behind the project?

Three University of Manitoba master of science students — Carlie Johnston, Tianci Fei and David Anokehi — work alongside Mohr. The University of Manitoba and Manitoba Agriculture collaborate on the science. The Western Grains Research Foundation (WGRF), Manitoba Crop Alliance (MCA), SaskWheat and the Sustainable Canadian Agricultural Partnership (Sustainable CAP) fund the work.

What should farmers watch next?

The first calibrated risk thresholds should emerge from the 2025 and 2026 field seasons. Watch for interim publications in late 2026 and a full platform launch with the project's close in 2027.