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Drilling down on carbon sequestration

New 10-year study looks for a more accurate formula to calculate the carbon-swallowing value of native grass

Ranchers in all three Prairie provinces are taking part in a decade-long study to assess the cumulative effect of different grazing systems on carbon sequestration and other ecological benefits from a working ranch.

In each province, 10 pastures managed under adaptive multi-paddock (AMP) grazing systems for at least 10 years will be paired with neighbouring pastures where cattle graze continuously or in rotations with only a few moves each growing season. A total of 60 tame and native pastures will be put under the looking glass for a decade.

AMP grazing is a term U.S. researchers use to identify what Canadian producers are more likely to think of as planned grazing, oftentimes involving higher stocking densities with faster moves through many more paddocks than traditional rotational grazing systems.

Participating producers need only manage their pastures as usual, while the research team does the work, explains Dr. Mark Boyce, a conservation biology and wildlife ecology scientist, who will be leading the project with Dr. Edward Bork, a rangeland scientist and Mattheis Chair in rangeland ecology and management, both professors at the University of Alberta.

This summer and next, the team will concentrate on drawing 45 one-metre-deep soil core samples from each site and doing plot measurements, such as plant diversity and plant cover. Soil biology will be analyzed as well as the carbon dioxide flux between the soil and atmosphere. The work will draw to an end with modelling to predict the potential of AMP and continuous grazing to sequester carbon in the various soil, vegetative and climactic settings.

ALUS Canada will communicate the findings when they become available. Funding from the Government of Canada for this project expires March 31, 2021.

Invited to be part of the scientific team are Steve Apfelbaum and Ry Thompson from the consulting firm Applied Ecological Services based in Wisconsin, and Dr. Richard Teague, Texas A&M AgriLife Research, who spoke about U.S. research on regenerative AMP grazing during the joint Western Canadian Holistic Management and Organics Alberta conferences at Lacombe, Alta.

The audience was treated to a screening of “The Luckiest Places on Earth,” a documentary showcasing the U.S. team’s project using the same study design on four Alberta ranches. Funded by Shell Oil Company, this project measured carbon storage among other ecological parameters and found AMP pastures had captured 0.75 to 2.5 tons of carbon per hectare per year more than the nearby continuously grazed pastures.

The documentary by Peter Byck, in collaboration with Arizona State University, features James Cross of Nanton, Tom and Margaret Towers of Red Deer, Tim Hoven of Eckville, and Blake Holtman of Taber. Just click on the Alberta section of the map on the homepage at www.soilcarboncowboys.com to view it and then move the pointer to “Saskatchewan” to watch the original 2014 “Soil Carbon Cowboys” documentary with Neil Dennis in Saskatchewan, Gabe Brown in North Dakota, and Allen Williams in Mississippi.

Boyce’s research on six ranches located in the area southeast of Calgary to Taber, indicates native grasslands store carbon at a rate of 1.4 to 2.4 tonnes per hectare per year. A scenario using this storage rate and the current Alberta carbon price of $25 per tonne could translate to a $35 to $60 per hectare payment, encouraging farmers to maintain permanent grassland for its many important ecological values.

“There is evidence that carbon sequestration is best in grassland and we anticipate that better-managed grass will do this better than conventional management,” says Don Campbell, a rancher and long-time holistic management coach from Meadow Lake, Sask., representing producers on the project’s steering committee.

“It’s only right if government is taxing people for putting carbon into the air, then those with the ability to remove it should be paid. We feel that we have a real solution in agriculture because raising the organic matter in soil by one or two per cent can sequester lots of carbon,” Campbell explains.

With the potential to increase soil organic matter, carbon storage year after year across Canada’s vast grazing and crop lands could be unlimited. This could create opportunities for payments from other countries as well for pulling carbon dioxide out of the atmosphere.

“U.S. studies on native grasslands have shown that AMP grazing is very efficient, but we don’t know the extent here in our environment with our shorter growing season,” Boyce says. “We think that there is a role for the biological method of carbon sequestration and storage, and that appropriate grazing will increase the amount of carbon sequestered and stored in the soils.”

Bork says this new study, and similar work by Teague’s group in the U.S. will start to bridge a big gap in the science between management effects on a landscape (ranch) scale and small-scale effects in individual plants seen in research.

A retrospective review of published research comparing continuous grazing to rotational grazing on rangeland over the past 60 years concluded rotational grazing isn’t superior to continuous grazing on rangeland. Rotational grazing has its place, purpose and benefits, but maybe isn’t as important in an agronomic sense as has been perceived and promoted because, overall, it didn’t improve either plant or animal production, according to the 2008 paper by Briske et al.

How is it then that producers, range managers and many other scientists have seen and continue to see beneficial results with rotational grazing at the ranch level?

Teague in a 2013 paper suggested “farmers and ranchers achieve superior results by the way they allocate resources, use different techniques, apply novel concepts and adaptively change elements to achieve outcomes that exceed the sum of parts involved. This is the art of farming.”

“Grazing and grasslands are complex systems on a large scale with added disturbances,” says Bork. “When disturbances occur — drought, frost or grasshoppers for example — producers adapt their management, often very quickly, to deal with it.”

On the other hand, experimental research by it’s very nature considers components singly and controls variables to the greatest extent possible to prove or disprove cause and effect one by one. These small-plot studies are completed in a very short time frame relative to the time it takes for animals to fully adapt to a new grazing regime and for its effects to become fully evident across the range.

Teague proposed an alternative approach by looking at ranches where AMP-style grazing practices have been in place for a long time to evaluate the cumulative effects of management on all ecological goods and services, forage production, pasture health, carbon sequestration and greenhouse gas uptake.

Bork says, “We are interested in understanding where, when and how management affects these ecological goods and services. If AMP grazing does improve beef and plant production and does favour greenhouse gas reduction, then that adds value. In general, research to date on rotational grazing is quite clear that there are benefits, but at what scale isn’t so clear.”

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