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Agriculture

Study shows that farmers storing carbon in their soil should focus on another greenhouse gas too

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Amy Mayer
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IPR file
Nitrous oxide, which is often known as laughing gas, is a powerful contributor to global warming. Some of it comes from the nitrogen that farmers apply to their fields as fertilizer.

New research from Iowa State University suggests farmers and policymakers should consider strategies to combat a powerful greenhouse gas that wet and soggy soils emit into the atmosphere.

Nitrous oxide, which is often known as laughing gas, is a powerful contributor to global warming. It locks heat in the atmosphere and is more potent than carbon dioxide, which some farmers have focused on capturing and storing in their soils to combat greenhouse gas emissions. Some of the nitrous oxide emitted into the air comes from nitrogen that farmers apply to their fields as fertilizer. The agriculture sector accounts for 10 percent of the nation’s greenhouse gas emissions, according to the U.S. Environmental Protection Agency.

The Iowa State researchers tested soils with different amounts of moisture and measured nitrous oxide emissions. They also synthesized data from other published studies. They found that the more poorly water drained from a field, the more nitrous oxide it belched into the air, but moderately-drained soils also emitted a lot of nitrous oxide. Steven Hall, an ecosystem ecologist in Iowa State's ecology, evolution and organismal biology department led the research.

“The climate impact of these nitrous oxide emissions can be twice as great as the possible climate benefits that we might get by storing more carbon in soil organic matter,” Hall said.

That’s why Hall said nitrous oxide emissions should be at the front of climate change conversations in agriculture.

“These nitrous oxide emissions can be consistently high from many of these agricultural soils and they need to be taken into account in terms of climate policy and in carbon markets,” Hall said.

Some farmers have reduced or stopped tilling their farmland to better store carbon and they’re getting paid for how much carbon they are able to pull from the air and store in the soil. Hall said it will take different practices to address nitrous oxide emissions, like decreasing the amount of nitrogen fertilizer they apply to their fields.

“Probably the low-hanging fruit for addressing nitrous oxide emissions is to think much more carefully about fertilizer management,” Hall said.