What’s that Green Stuff?

Regulating Eutrophication and Nitrogen Runoff in Wisconsin Lakes

by Annabelle Himstreet on April 27, 2026

Wisconsin and similar agricultural states use large amounts of fertilizer (both synthetic and natural) for crop production. According to the Wisconsin Department of Agriculture, Trade and Consumer Protection, the 2023-2024 season saw 139,191 tons of “Agricultural Fertilizer” distributed throughout the state. Note that there is no public means of reporting applied fertilizer under Statute 94.64(6m); however, businesses are required to report to the state the annual tonnage dispersed in Wisconsin. 

Primary plant nutrients, common in both synthetic and natural fertilizers, include nitrogen, phosphorus, and potassium (University of Nebraska). Nitrogen, especially, is difficult to find naturally in its purest form due to the difficulties of fixing nitrogen within soil at the high volumes necessary for large-scale agricultural production.   

Agricultural fertilizers, particularly synthetic ones, are among the most influential developments of the Green Revolution. Dan Alloso, in his book American Environmental History, ascribes chemical fertilizers to the agricultural industry’s ability to “feed the world’s population.” Clearly, with a population on the rise, managing food systems remains critical, particularly with respect to food security. 

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However, some environmental hazards arise from the use of man-made nitrogen, including eutrophication of neighboring waterways. Eutrophication describes the rapid increase in “the amount of plant and algae growth” as a result of an influx of nutrients to the water – often from soil runoff (National Ocean Service). These algal blooms eventually decompose, producing carbon dioxide and ultimately altering the pH and creating hypoxic waters that are detrimental to fish and their ecosystems. 

Soil runoff, particularly in Wisconsin, contains excessive amounts of nitrogen from fertilizer used in crop production and livestock management – especially CAFOs. According to the Environmental Working Group, in 2022, Dane County alone had 4,207 tons of “N overload”. Given the density and proximity of lakes and rivers in the region, surface runoff containing this abundance of nitrogen filters into those nearby water systems, causing eutrophication, as described previously. 

The Clean Water Act includes regulatory measures to combat water pollution, including contamination of drinking water. As of Feb. 2026, the EPA regulates agricultural “sewage sludge” such as arsenic and lead. However, the agency lacks specific legislation for managing nutrient pollution from both livestock production and commercial fertilizers. 

Agricultural runoff is listed under section 502(14) of the Clean Water Act, as a form of “nonpoint source pollution”, meaning it does not come from a confined or specific origin. The Clean Water Act and other environmental legislation lack the capacity to regulate nonpoint source pollution specifically, given that it's virtually impossible to trace back to individual culprits. Nutrient pollution remains a broader systemic concern for the agricultural industry rather than an individual fault. However, the lack of federal oversight in this matter fails to mitigate ongoing water contamination across the country, not just in Wisconsin.

Unlike federal standards, Wisconsin has a lengthy series of regulations on when, where, and how fertilizer is applied to soils. In addition to regular soil testing every four years (Ch. ATCP 51, Appendix B (A.c)), the state requires that the “available nitrogen from all sources shall not exceed the annual N requirement of non-legume crops” on agricultural fields (Chapter ATCP 51, Appendix B (A.f)). 

Additionally, the state mandates nitrogen runoff controls, despite the federal nonpoint-source contention, noting that runoff should not occur “during or immediately after application” and that any violators must take “corrective action to prevent offsite movement” (Chapter ATCP 51, Appendix B (A.f)). Wisconsin’s heightened regulations meet the needs of the region, given the area’s rich agricultural production and the state's conservationist history, rooted in Indigenous tribes and scholarly study, including Aldo Leopold.

While noteworthy, Wisconsin’s local regulation of nutrient pollution remains limited in scope, as it lacks cleanup efforts for later down the line, when runoff at the end of growing seasons seeps into local groundwater and waterways. While it is understandably difficult to prosecute pollution beyond the control of individual actors, potential regulations could involve stricter enforcement rules and protocols for managing eutrophication once it begins.

The vague federal jurisdiction over nonpoint source pollution does little to help this matter, as it can encourage states to deregulate commercial fertilizer and agricultural practices. Ultimately, exacerbating the broader systemic issue of overreliance on synthetic fertilizer in lieu of healthier soil management practices that may prevent or mitigate nutrient-induced water pollution.