Perennial Crops Key To GHG-Neutral Crop Production

Reducing greenhouse gas emissions is more than a public service – it can save farmers money, a soil scientist with the University of Manitoba says.

Mario Tenuta says farmers don’t seem worried about the greenhouse gases (GHGs) they produce while growing food, despite the link with climate change.

But farmers can benefit from reducing emissions of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4), including the potential to earn revenue from carbon offsets.

But more importantly, they can save money in reduced fertilizer purchases and improved soil health, Tenuta, a professor of soil microbiology and Canada Research Chair in Applied Soil Ecology told the 54th annual meeting of the Manitoba Soil Science Society in Winnipeg Feb. 3

“It (reducing GHGs) should translate to more profitability (for farmers),” Tenuta said.

“Farmers don’t really care about this (climate change). The message doesn’t hit home. We’ve heard about it for decades, it’s just not sinking in.”


Farmers are more likely to consider cutting emissions when they learn about the other benefits, Tenuta said.

Crops can be grown in a way that is GHG neutral, Tenuta said, citing research he and his colleagues have conducted at the University of Manitoba’s Glenlea Research Station. But it requires growing alfalfa for three years (including the establishment year), for every two years of annual crop production, he said in an interview following his presentation.

If Manitoba farmers grow more alfalfa they’ll want to have markets for it. Most alfalfa is fed to cattle. While Manitoba has cow-calf producers and back-grounders, most cattle are fattened in Alberta feedlots. One solution would be to feed cattle here longer, Tenuta said.

“Put the animals back where the food is for them rather than transport the food around for them,” he said.

“The key thing is if we finish them on forages and grasses it needs to be a high-protein finish. If it’s a low-protein finish then they’re going to be producing more methane through their gut.”

There has been lots of talk about farmers earning money by storing carbon. The thinking is it’s easier and cheaper for high GHG emitters to pay farmers to cut their emissions.

“In my opinion the benefits to the soil are more important than carbon credits,” Tenuta said. “With carbon credits we’re not talking mega dollars, we’re talking about a few dollars an acre.”


For example, cutting nitrous oxide emissions means the nitrogen farmers apply to grow their crops will be better utilized. More will go to crop and less into the atmosphere.

More carbon in the soil translates into improved levels of organic matter, resulting in better drainage and tilth. That in turn makes for a better environment for crops to grow and it makes the land easier to work, resulting in less fossil fuel being burned and lower GHG emissions.

In Canada 78 per cent of the GHG emissions come from transportation– driving trucks, cars, trains and planes. But seven per cent comes from nitrous oxide, most of which is the result of farmers applying nitrogen fertilizer or manure to their crops, Tenuta said.

Fourteen per cent of the GHGs are from methane, most of which comes from belching cows.

The breakdown is a lot different in Manitoba where 35 per cent of the GHGs come from agriculture, Tenuta said.

Despite the concerns surrounding GHG emissions, including the link to climate change, farmers must apply nitrogen (or nitrogen containing manure) to crops or crop yields will decline, Tenuta said. Most crops in Manitoba remove 50 to 160 kilograms of nitrogen per hectare. The nitrogen that’s removed – often exported as grain to other countries – must be replaced.


As farmers increase nitrogen applications to try to maximize yields, there’s more chance that nitrous oxide will be lost to the atmosphere.

Just replacing the nitrogen that has been removed by crops will result in nitrous oxide emissions, especially with annual crops versus a perennial such as alfalfa because seedling crops tie up less nitrogen in the spring and mature and shut down in the fall.

Established alfalfa is actively growing sooner in the spring and grows longer in the fall, Tenuta said. [email protected]




About the author


Allan Dawson

Allan Dawson is a reporter with the Manitoba Co-operator based near Miami, Man. Covering agriculture since 1980, Dawson has spent most of his career with the Co-operator except for several years with Farmers’ Independent Weekly and before that a Morden-Winkler area radio station.



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