By Chris Vervaet
The cropping system that supplies Canadian canola has been transformed over the past several decades to one that is more environmentally sustainable and profitable. This transformation is resulting in increases in soil organic carbon (SOC), primarily from the reduction in summer fallow (intentionally leaving land without vegetation for one year) and reduction in tillage, including the large-scale adoption of no-till practices. This increase in SOC represents a significant removal of carbon dioxide from the atmosphere so it is quantified in Canada’s official greenhouse gas (GHG) inventory. Quantification supports the inclusion of changes in SOC due to regenerative farm practices when estimating the carbon footprint of canola and other crops.
SOC is carbon in the soil derived from plants and animals. Green plants grow by converting carbon dioxide from the atmosphere via photosynthesis into carbon-containing materials. These organic materials are added to soil from the plants themselves. Any increase in SOC is a net removal of carbon dioxide from the atmosphere because photosynthesis was the source of the SOC. Conversely, any decrease in SOC is a net emission of carbon dioxide to the atmosphere. The increase in SOC is often described as carbon sequestration or a soil sink.
Today’s Cropping Systems Support SOC
Over the past 30 years, Canada’s cropping system was transformed from one that was primarily frequent fallow (32 percent of cropland) and intensive tillage (80 percent of cropland) to the SOC regenerative cropping system of today, where only 3 percent of cropland is under fallow and less than 20 percent is intensively tilled. The conversion of fallow land to annual crop production and the dramatic shift in tillage practices support SOC gains in two ways:
- Increasing carbon input into soil: Less fallow and more land dedicated to crops means more vegetation, crop residue and organic materials (leaves, roots, etc.), which are high in carbon content, are added to the soil.
- Decreasing carbon losses from decomposition: Less or no tillage means less soil disturbances, which reduces organic material from exposure to decomposition. More carbon is left in the soil.
Canola’s Contribution to SOC Gains
Canola has been instrumental in supporting SOC gains and carbon sequestration from crop production in Canada, responsible for 70 percent of the growth in carbon sequestered since 2015[i]. Much of the conversion of summer fallow in Canada can be attributed to the rapid expansion of canola acres in recent decades (see chart below). Canola also produces more biomass than many other crops and therefore has a relatively higher carbon input to the soil. Although this is not currently being measured in Canada’s SOC reporting, canola’s deep roots allow for carbon to be stored underground permanently.
Source: Statistics Canada
Quantification of SOC
Quantifying SOC changes over time and/or over soil landscapes has been the subject of decades of research, investigation, peer-reviewed scientific papers and regulatory discussion in Canada. The foundation of this work is an extensive, cross-country network of past and current long-term agricultural field measurement studies conducted by Agriculture and Agri-Food Canada research stations and universities. Combining real SOC measurements with statistics on land use-management practices, like summer fallow conversion and tillage, underpin and validate the SOC changes reported by Canada in its National Inventory Report. The chart below illustrates these changes, showing significant GHG emission sequestration (or removals) from summer fallow conversion/crop residue and tillage practices associated with crop production, except for years of severe drought.
Source: 2023 Canada’s National Inventory Report
Canada’s cropping system achieves a large removal of carbon dioxide emissions from the atmosphere due to the use of soil-improving practices for its production. This is captured in Canada’s official estimates of GHG emissions, demonstrating that accurate quantification of SOC change on aggregate is feasible. Including SOC change estimates confirms Canadian canola has a low-carbon intensity.
Chris Vervaet is executive director of the Canadian Oilseed Processors Association in Winnipeg, Manitoba.
[i] Jianling Fan, Brian G. McConkey, B. Chang Liang, Denis A. Angers, H. Henry Janzen, Roland Kröbel, Darrel D. Cerkowniak, Ward N. Smith, Increasing crop yields and root input make Canadian farmland a large carbon sink. Geoderma, Volume 336, 2019, Pages 49-58, ISSN 0016-7061, https://www.sciencedirect.com/science/article/abs/pii/S0016706118305755?via%3Dihub