U of M study: Pollution from Minnesota's cornfields worse than previously thought

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Who would have thought the U.S. Corn Belt was producing so much greenhouse gas?

The University of Minnesota apparently had its suspicions, with a new study showing that potentially harmful nitrous oxide emissions from rivers and streams connected to Minnesota's cornfields have been grossly underestimated.

But researchers say the culprit isn't the corn – it's the fertilizers used to make it grow, according to a news release.

The U of M says runoff from the fertilizer creates greenhouse gases downstream, at a rate that may be nine times greater than previously thought.

In fact, researchers believe the Intergovernmental Panel on Climate Change, a United Nations group, may have been off by as much as 40 percent in their measurement of agricultural nitrous oxide emissions.

"This study provides a key piece to solving that puzzle and will help land managers and scientists develop better strategies for mitigating nitrous oxide emissions," said U of M Professor Tim Griffis in the release.

Why were the estimates so far off?

One of the reasons accurate measurements were difficult to take is apparently the differing sizes and flows of the rivers and streams being measured – the release says the researchers discovered a "strong relation" between the emission strength of a stream and its size.

Additionally, they found that the smallest streams, "or those with the closest connections to the land," had the strongest concentrations of nitrous oxide.

Nitrous oxide, MPR says, is about "300 times more potent" than carbon dioxide, another potential contributor to global warming.

So what happens next? The U of M says the goal now is to confirm that "nitrous oxide degassing" also occurs in other countries that rely heavily on nitrogen fertilizers in their agricultural production, like China and India.

The report was published by the Proceedings of the National Academy of Science of the United States of America.

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