Additional fine-tuning of updated Nutrient Reduction Strategy is needed
An updated state Nutrient Reduction Strategy (NRS) could help Minnesota meet its 2040 nutrient reduction goals and ensure the vitality of the state’s corn farmers. But the current draft of the updated NRS, as published by the Minnesota Pollution Control Agency (MPCA) this summer, needs additional fine-tuning to meet those objectives.
That was the gist of comments submitted on September 10 by the Minnesota Corn Growers Association (MCGA) to MPCA.
The updated NRS includes baseline assumptions on the effectiveness of nitrogen removal practices—which underpin MPCA’s modeling for reaching 2040 goals—that have limited application to Minnesota’s corn farmers, MCGA said in its comments. Many of the suggested practices are based on data gathered from research conducted outside of Minnesota. Given the state’s unique soils, climate, and cropping system, the effectiveness of nitrogen removal practices are different in Minnesota than in other states. Instead, more research should be done to quantify the effectiveness of nitrogen removal practices in Minnesota.
The document also minimizes the effectiveness of in-field nutrient management practices at reducing nutrient runoff as simply having “limited potential.” Collective improvements across large acreage can have a significant impact, MCGA noted.
Furthermore, the modeled scenarios for reaching the 2040 goals are unrealistic in terms of their scalability, MCGA said. For example, one of the scenarios incorporates a 25-fold increase in field edge tile water treatment over current adoption levels. It’s highly unlikely the practice could be scaled to such an extent without substantial government assistance.
MCGA also said one of MPCA’s explanations for changes in nitrogen losses—more tile drainage—should be updated to account for all nitrogen loss pathways. The document fails to note that without tile drainage, soils can be more susceptible to saturation, which can lead to significant nitrogen losses via denitrification resulting in nitrous oxide losses to the atmosphere.
The report also cites increasing row crop acreage as a factor contributing to increased nutrient losses. MCGA noted that the document includes a statistic—an increase of 140,000 acres of corn/soybeans annually since 1982—that overstates certainty and does not reflect current realities in year-to-year variability in acreage. In reality, there is no statistical trend observed over the last 10 years. In fact, more than 300,000 acres of total cropland have been lost in the state since 2018, according to the Board of Water & Soil Resources.
Additionally, MCGA said the updated NRS should be cautious in recommending that fertilizer sales data be used as a proxy for fertilizer application rates and therefore as a foundation for local nutrient reduction strategies. Instead, the updated document should recommend targeting rotation years where over-application is potentially occurring and promoting broadly applicable practices such as timing, split applications, variable-rate fertilization, and enhanced incorporation, MCGA said. It should also rely on soil testing to monitor potential phosphorus build-up.
SAF and winter oilseeds
Additionally, MCGA noted a problematic statement in a section of the document that recommends a new statewide campaign to increase perennial and cover crop acreage. As part of that effort, the section recommends supporting initiatives to develop markets for perennials and cover crops, including through sustainable aviation fuel (SAF). It then says that “if SAF is based on corn instead of CLC, this could work against making nutrient reduction progress in our waters.”
Unfortunately, this statement overlooks MPCA’s own admission that “insufficient data” exists for winter oilseed relay crops relative to nitrate leaching. The one data point MPCA included on the potential of winter oilseeds comes from a report commissioned by an advocacy group that has not been published in peer-reviewed literature. MCGA recommends omitting the report from the updated NRS.
MCGA also noted problematic statements in the document suggesting that federal farm policy prevents widespread adoption of perennials and cover crops. Instead, the NRS should be revised to accurately reflect federal policy opportunities that enable farmers to adopt cover crops and perennials while managing risk.
MCGA said MPCA should prioritize farm-level cost share programs and assess existing tools and programs before creating new ones. For example, the updated document lists eight potential tools to support NRS progress tracking, but it doesn’t recommend tools that are designed to directly support farmer decision-making. Additionally, the document should recommend offering the University of Minnesota Extension Nitrogen Smart Program as an alternative to developing a nitrogen endorsement for the Minnesota Agricultural Water Quality Certification Program.
MPCA plans to finalize the document by the end of 2025. MCGA will continue to closely follow the process as part of its efforts to support Minnesota’s corn growers. MCGA was also a signatory with other agriculture groups on a comment letter submitted by the Minnesota Ag Water Resources Center. Read more of MCGA’s comments to MPCA on the strategy here.
