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While still much less of a factor than industrial sources of pollution, the greenhouse-gas spewed out by croplands shouldn’t be ignored, she said, noting that it also degrades the Earth’s ozone layer.

“It’s a side effect of agriculture that could be addressed with some relatively simple measures,” said Wagner-Riddle. “We are always going to have to eat, so this is not going to go away.”

Farmers are, in fact, concerned about their industry’s part in the climate-change phenomenon, which also includes methane emissions from livestock manure, said Bonnett.

But some of the recommended measures are costly — and could undercut Canadian producers’ competitiveness if the U.S. government does not insist on similar steps, he said.

Bonnet said farmers need incentives to take action, like the cap-and-trade system more typically associated with power plants and other fossil-fuel burning polluters.

Nitrous oxide — commonly known as laughing gas and used as a dental anesthetic — accounts for well under 10 per cent of greenhouse gas emissions. But it’s almost 300 times as potent as carbon dioxide at trapping energy, the greenhouse effect believed to be warming the planet.

It has long been known that agriculture is a prime source of nitrous oxide emissions, due largely to the nitrogen-based fertilizers used to produce food worldwide.

But largely overlooked was the impact of fields in northern climates that freeze during the winter and then thaw, said Wagner-Riddle, whose study was published in the journal Nature Geoscience.