Voluntary Is Not Enough: States Need to Intervene to Address Nitrogen Pollution

As part of Minnesota’s first Nutrient Reduction Strategy in 2014, the state built a network of voluntary programs aiming to tackle nitrogen pollution. In theory, programs like water quality certification, value chain enhancement of perennial systems, and conservation drainage projects were all designed to promote adoption of practices that manage nitrogen runoff.  

But according to midpoint data on Minnesota’s nitrogen reduction targets, results have been underwhelming. Despite a decade of investment, nitrogen pollution statewide has only declined between 6 to 9 percent, well below the 20 percent reduction target set for 2025. To stay on track for the state’s 2040 goal of a 45 percent total nitrogen reduction, nearly all additional progress must come from the agricultural sector. The Minnesota Pollution Control Agency (MPCA) itself recognizes that scaling up voluntary programs compared to historic adoption rates may not be feasible.  

The stakes are high if Minnesota keeps missing its targets. One in eight Minnesotans rely on groundwater with elevated nitrate levels as their primary drinking water source. In the southeastern part of the state, these numbers are higher. In 2017, 19 percent of the wells tested in Winona County exceeded the state’s nitrate health risk limit of 10 milligrams per liter (mg/L). In Fremont Township, half of the tested wells exceeded that limit. Additionally, from 2010 to 2020, six Minnesota communities faced financial costs, collectively above $3 million due to harmful algal blooms fueled by high nitrogen loads in surface waters. This pollution flows downstream of the Mississippi River, contributing to the Gulf of Mexico’s annual hypoxic zone and sickening animals like sea turtles. A study linked nitrogen pollution to green sea turtles developing horrific and often deadly tumors on their heads, eyes, and flippers.   

MPCA has reported that since 2014, four million acres have been enrolled in conservation programs that promote practices designed to reduce nitrogen loss—about 15 percent of the state’s agricultural land. Yet actual nitrogen reductions from these practices are only between 4 to 5 percent. These marginal water quality improvements demonstrate two key shortcomings that characterize voluntary programs across the country. Utilizing proxy data, like acreage enrolled and theoretical estimates for load reductions, limits the accuracy and tracking of actual improvements at field or watershed scale. Without outcome-focused metrics, communities and decision-makers cannot determine whether programs are reducing nitrogen pollution in a meaningful way.  

Voluntary efforts to limit nitrogen from running off the field also do not get to the heart of the problem: We are applying too much nitrogen to begin with. Nitrogen fertilizer and manure applied to croplands in Minnesota exceeded the recommended rates by 18 percent on average. This means there is significant room to reduce application rates without affecting crop yields. Evidence suggests that smarter fertilizer management, including reducing rates and improving timing, could dramatically reduce nitrogen runoff.  

To make real progress, states with significant agricultural nitrogen pollution should take two critical steps: 

1. Build outcome-focused data collection and reporting systems 

   You can’t fix what you don’t measure. It is not enough for state agencies to rely on general metrics like the number of acres enrolled in certain conservation practices or nutrient reduction programs. This information does not measure or track direct progress toward the intended outcome of reduced nitrogen pollution. Instead, states need data on field-level nitrogen applications from fertilizer, manure, and compost. Measures should also include improved fertilizer sales reporting and increased groundwater testing in areas vulnerable to nitrate contamination. These metrics will provide the state with a clear picture of where to direct their resources to achieve the greatest impact and whether programs are effective.  

2. Move beyond voluntary programs to adopt enforceable limits 

   Voluntary programs have been tried, and the results are clear: These approaches cannot deliver the necessary reductions in nitrogen pollution on their own. However, other regions demonstrate that enforceable limits on nitrogen overapplication, combined with voluntary programs, cuts leaching and steadily improves water quality while protecting agricultural production. 

   In 1991, the European Union (EU) adopted the Nitrates Directive in response to widespread groundwater contamination from overapplication of nitrogen. The Nitrates Directive required EU nations to designate nitrate-vulnerable zones and limit the application of nitrogen in these areas. A 2019 estimate showed that excess nitrogen from agriculture had been reduced by 33 percent across the entire EU, and this reduction was much higher in regions that had adopted stronger regulations. For instance, nitrate loads in Denmark’s streams fell 30 to 50 percent between 1990–2018, and nitrate loads in coastal waters fell by 45 percent. Similarly, New Zealand recently implemented a nationwide fertilizer application rate limit, with early data showing 15 to 32 percent reductions in nitrate leaching. 

   Agricultural lobbying groups are quick to claim that any limits on fertilizer will drive them out of business. However, since the EU’s Nitrates Directive in 1991, agricultural industry output has increased, and EU farm income per worker was 56 percent higher in 2021 than in 2013, far outpacing the 9.4 percent inflation during the same period. 

In 2025, numerous states in two of the largest watersheds in the United States missed critical final and midpoint nutrient reduction targets. After more than 15 years of widespread implementation of voluntary efforts, it’s clear that additional approaches are needed. Excess nitrogen continues to contaminate drinking water, degrade ecosystems, and accelerate climate change. Nitrogen overapplication also comes with an economic cost, both to farmers who pay unnecessary input costs and to communities who pay for costly treatment of contaminated water.  

But this year also offers a new opportunity for states to break from the past and chart a new course, and we are urging officials to act in Minnesota and California. With stronger data collection and outcomes-based reporting, states can finally effectively measure and track the effectiveness of their policies and programs. And with stronger approaches to limiting fertilizer overapplication, states can achieve real reductions in nitrogen pollution. We can and must grow food in a way that doesn’t poison drinking water, kill wildlife, and degrade ecosystems.