EWG analysis finds farm emissions from fertilizing ‘continuous corn’ crops fueling climate crisis

Fertilizing massive “continuous corn” crops across the Midwest is a major driver of greenhouse gas emissions, a new Environmental Working Group analysis shows. But proven conservative practices could dramatically cut farming’s contribution to climate change.

The new report, focused on four Corn Belt states, draws extensively on cropland and climate data from the Agriculture Department. It highlights the outsize climate toll of continuous corn – when farmers grow corn on the same field year after year. Nearly 15 million acres in Illinois, Iowa, Minnesota and Wisconsin are planted this way, representing one-fifth of all cropland across those states.

Corn is the most nitrogen-fertilizer-intensive crop in the U.S. and accounts for more than two-thirds of all nitrogen fertilizer use nationwide. Nitrogen fertilizer is applied to crops and interactions in the soil turn it into nitrous oxide, a greenhouse gas roughly 300 times more powerful than carbon dioxide. Agriculture produces nearly 80% of all nitrous oxide emissions in the U.S., four times more than all other sectors combined.

Applying nitrogen fertilizer to continuous corn crops also leads to nitrate pollution of drinking water. Drinking tap water contaminated with nitrate can increase the risk of health harms, including several types of cancer.

“Continuous corn locks farmers into a system that demands enormous amounts of fertilizer and creates climate emissions,” said Anne Schechinger, EWG’s Midwest director and lead author of the report.

“But even modest investments in regenerative conservation practices could help farmers shrink agriculture’s climate footprint while protecting drinking water and public health,” she said.

Small investments for big payoff

Nitrous oxide emissions account for 52% of U.S. agricultural greenhouse gases. Corn production alone generates more than half of agriculture’s nitrous oxide emissions.

Overall, U.S. agriculture is responsible for roughly 10% of the country’s total greenhouse gas emissions from all economic sectors. With climate change intensifying, farmers are under mounting pressure to shrink their greenhouse gas footprint and keep agriculture from overtaking other sectors as the nation’s top source of climate pollution. Projections show farm-related emissions rising by roughly 0.25% annually through 2050.

EWG’s analysis finds that adopting just four proven conservation practices on a small fraction of continuous corn acres could yield major climate benefits.

The practices are riparian forest buffers, tree or shrub establishment, hedgerow planting and windbreak establishment. Implementing each practice on just 1% of continuous corn acres across the four Corn Belt states would cut total greenhouse gas emissions from those acres by 3.67 million metric tons every year. That’s equivalent to taking more than 850,000 gas-guzzling cars off the road.

“These are relatively small changes with outsized impacts,” said Al Rabine, EWG GIS analyst and co-author of the report. “Planting trees or shrubs along the edges of cornfields can sequester carbon, cut nitrous oxide emissions, and reduce water pollution – a triple win for farmers, communities and the climate.”

The report also highlights the climate benefits of working lands practices that allow farmers to keep entire fields in production, such as adopting no-till, using cover crops, switching to different fertilizer types and diversifying crop rotations.

Beyond emissions, drinking water is at risk

EWG’s analysis shows that fertilizer use on continuous corn doesn’t just fuel climate change – it also contaminates drinking water.

Nitrate pollution, a byproduct of fertilizer runoff and leaching to water, has been linked to cancers and birth defects. In regions like southeast Minnesota, where karst soils allow contaminants to easily seep into groundwater, nitrate in private well water already poses serious health risks.

EWG’s Tap Water Database, updated in February, shows the extent of nitrate drinking water contamination in the U.S. Tap water systems in agricultural areas often have the highest nitrate concentrations. Private drinking water wells can also have unsafe levels of nitrate, especially when near animal farms and intensively fertilized fields, or where septic tanks are used.

The Environmental Protection Agency in 1992 set a limit of 10 milligrams per liter for nitrate in drinking water. The agency has never updated this limit, despite it being decades old. Epidemiological research suggests that the EPA’s nitrate limit does not sufficiently protect public health from cancer risks.

Policy reforms needed

Some farmers are adopting regenerative practices, which generally refers to efforts that aim to improve soil health and that might have climate benefits.

EWG’s report stresses that, even with those efforts, far more crop acres must be put into conservation – and quickly. That requires reforms to federal and state farm programs.

The 2022 Inflation Reduction Act initially boosted funding for climate-smart conservation practices. But the One Big Beautiful Bill Act, enacted in July, stripped all climate-smart designations. As a result, additional federal funding to farmers will no longer prioritize practices that reduce greenhouse gas emissions.

EWG recommends updating federal programs like the Environmental Quality Incentives Program to:

• Prioritize practices proven to cut greenhouse gas emissions
• Cover up to 90% of costs for legitimate regenerative practices
• Support longer-term contracts with farmers, between three to five years, ensuring conservation measures stay in place over time

Changes to federal farm subsidies could also encourage farmers to diversify crop rotations instead of planting continuous corn year after year.

Key findings

Some of the most important findings from the report:

• Fifteen million acres in Illinois, Iowa, Minnesota and Wisconsin are used for continuous corn, representing 20% of harvested cropland.
• Continuous corn requires massive nitrogen fertilizer use, fueling greenhouse gas emissions, including from nitrous oxide, that contribute to climate change.
• Nitrous oxide is 273 times more potent than the greenhouse gas carbon dioxide and stays in the atmosphere for over 100 years.
• Adopting key conservation practices on just 4% of continuous corn acres total in these four states could cut greenhouse gas emissions equivalent to removing 850,000 cars annually from the road.