The environmental costs of corn: should the US change how it grows its dominant crop?

For decades, corn has reigned over American agriculture. It sprawls across 90m 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 the US’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 the nitrogen in the fertilizer 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.

The corn and ethanol industries insist that rapid growth in ethanol – which now consumes 40% of the US corn crop – is a net environmental benefit, and they strongly dispute research suggesting otherwise.