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For decades, corn has reigned over American agriculture. It sprawls across 90 million acres — about the size of Montana — and goes into everything from livestock feed and processed foods to the ethanol blended into most of the nation’s gasoline.
But a growing body of research reveals that America’s obsession with corn has a steep price: The fertilizer used to grow it is warming the planet and contaminating water.
Corn is essential to the rural economy and to the world’s food supply, and researchers say the problem isn’t the corn itself. It’s how we grow it.
Corn farmers rely on heavy fertilizer use to sustain today’s high yields. And when that nitrogen breaks down in the soil, it releases nitrous oxide, a greenhouse gas nearly 300 times more potent than carbon dioxide. Producing nitrogen fertilizer also emits large amounts of carbon dioxide, adding to its climate footprint.
Agriculture accounts for more than 10% of U.S. greenhouse gas emissions, and corn uses more than two-thirds of all nitrogen fertilizer nationwide — making it the leading driver of agricultural nitrous oxide emissions, studies show.
The corn and ethanol industries insist that rapid growth in ethanol — which now consumes more than 40% of the U.S. corn crop — is a net environmental benefit, and they strongly dispute research suggesting otherwise.
Since 2000, U.S. corn production has surged almost 50%, further adding to the crop’s climate impact.
Yet the environmental costs of corn rarely make headlines or factor into political debates. Much of the dynamic traces back to federal policy — and to the powerful corn and ethanol lobby that helped shape it.
The Renewable Fuel Standard, passed in the mid-2000s, required that gasoline be blended with ethanol, a biofuel that in the United States comes almost entirely from corn. That mandate drove up demand and prices for corn, spurring farmers to plant more of it.
Many plant corn year after year on the same land. The practice, called “continuous corn,” demands massive amounts of nitrogen fertilizer and drives especially high nitrous oxide emissions.
At the same time, federal subsidies make it more lucrative to grow corn than to diversify. Taxpayers have covered more than $50 billion in corn insurance premiums over the past 30 years, according to federal data compiled by the Environmental Working Group.
Researchers say proven conservation steps — such as planting rows of trees, shrubs and grasses in corn fields — could sharply reduce these emissions. But the Trump administration has eliminated many of the incentives that helped farmers try such practices.
Experts say it all raises a larger question: If America’s most widely planted crop is worsening climate change, shouldn’t we begin growing it a different way?