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Perennial Crops May Store Carbon

Finding ways to make farming more environmentally sound is one of the goals of a greenhouse gas study taking place south of Winnipeg.

“What we’re trying to do is to see if it’s possible to generate cropping systems that are greenhouse gas neutral; in other words we want to build up soil carbon and prevent carbon loss, or at least minimize it,” said Mario Tenuta, lead investigator at the Trace Gas Manitoba Greenhouse Gas Research Site near the Glenlea Research Station.

Tenuta, along with Brian Amiro and students from the University of Manitoba, took colleagues, farmers and peers on a tour of the research site Aug. 31. The research is sponsored by the Canadian Fertilizer Institute, Natural Sciences and Engineer ing Research Council of Canada, Canadian Foundation for Innovation and the Manitoba Rural Adaptation Council.

The large site has been up and running since 2005 and will continue to operate for several more years, investigating ways to reduce emissions of nitrous oxide, methane and carbon dioxide. The project is also tied to other greenhouse gas research projects taking place throughout the province.

“Agriculture is a major greenhouse gas producer, second next to the transportation industry … so we want to provide some solutions through nitrogen fertilizer management for example, the use of perennials to store carbon and so forth,” explained Tenuta.

To monitor emissions from the four test plots, gas intakes and soil moisture and temperature stations have been set up in the centre of each plot, feeding information back to a centrally located tunable diode laser instrument that measures emissions continuously, rotating from plot to plot.

Some plots are home to annuals and have rotated through corn, faba bean, wheat, rapeseed and barley crops. This season the two annual plots are hosting wheat. The perennial test plots have grown alfalfa since 2008.

Tenuta notes the perennial crops have been good at storing carbon in the soil, and don’t require the fertilizer that annual crops do, resulting in fewer gas emissions. Still unknown is whether the soil continues to hold the carbon placed there by the alfalfa after the perennial crop is removed.

The annual crops appear to have greater difficulty holding on to carbon, and the study has shown they continue to lose carbon even after harvest, according to the researchers.

“That was quite surprising, because you tend to think at that point that it should be carbon neutral,” said Tenuta. He added that depending on other conditions, the amount of carbon saved by a crop can be nullified by the amount of nitrous oxide produced when fertilizer is used.

“Spring wheat usually stores carbon in the soil, but the nitrous oxide that is emitted with the fertilizer generates greenhouse gas, so we’re still generating greenhouse gas overall,” said the researcher, noting nitrous oxide is often released in bursts in the Red River Valley following changes in temperatures, like during the spring thaw, and when fertilizer application occurs.

Another surprising result to come from work done so far is that pasture land, when wet, can produce methane.

And although there was no shortage of water at the research site this spring, current conditions have left the area bone dry. However, Tenuta doesn’t believe the variations in weather conditions will negatively impact the research.

“We think that what we’re seeing here in terms of challenges and excess moisture, and the fact it is too dry now, is the same as what farmers face. So if anything we’re doing some very real-life work here, more so than with small plot comparisons when you go onto better land,” he said.

Each plot at the site is four hectares, requiring commercial- scale equipment to be used. Each plot also has varying characteristics, including dry and wet areas. This spring, the edges of one of the wheat plots was hit with fertilizer broadcast by a neighbouring farmer, causing unexpected plant development.

“You’re a little nervous as a scientist, because you kind of want everything to be perfect, but these are large plots,” Tenuta said. “We do have bad patches, but that is part of the study. We can’t exclude them from our research, just like a farmer can’t exclude them from their crop.”

Amiro notes the next step is to research the role of greenhouse gases beyond the field, by including the effect of equipment use and animal consumption.

“There is no doubt that perennials are more greenhouse gas friendly, but the question is how do we get them into the rotation, because perennials end up being eaten by cattle and cattle actually emit methane as a result of internal fermentation,” said Amiro. “We still have to pull all that together.”

He noted that research is being done on the development of perennial wheat and rye crops, but that so far yields have been low. However, if fully developed, a perennial grain could reduce greenhouse gas emissions substantially.

“But whatever we do, in the end, must still be economically viable for the farmer,” Amiro added.

shannon. [email protected]



patches,butthatispart ofthestudy.Wecan’t excludethemfrom ourresearch,justlike afarmercan’texclude themfromtheircrop.”


About the author


Shannon VanRaes is a journalist and photojournalist at the Manitoba Co-operator. She also writes a weekly urban affairs column for Metro Winnipeg, and has previously reported for the Winnipeg Sun, Outwords Magazine and the Portage Daily Graphic.



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