This study compares nitrous oxide emissions and soil carbon in side-by-side long-term organic and conventional production systems including oats, wheat and flax. As legumes are a common source of nitrogen in organic systems, the study will also test annual legume management systems to determine best practices to reduce nitrous oxide emissions and increase nitrogen use efficiency.
Research Objectives
- Compare organic and conventional production in terms of N20 emissions over a growing season.
- Compare organic and conventional production in terms of soil C storage over the long-term (32 years).
- Determine the GHG footprints of organic wheat, oats and flax compared with conventional production.
- Evaluate how mixing legume green manure cover crops with non-legume plant species affects N20 emissions during and after the green manure phase.
- Evaluate how reducing tillage in the legume green manure cover crop termination phase affects N20 and ammonia emissions after legume termination.
Related Resources
Progress and Results
Research Update (March 2026)
KEY TAKEAWAYS
- Martin Entz retired and the research activity was paused for 2025-2026.
- As of April 2026, Dr. Michelle Carkner has taken on the role of Lead Researcher. A modified workplan will be completed over the next two years.
Research Update (March 2025)
KEY TAKEAWAYS (PRELIMINARY OBSERVATIONS)
- Nitrous oxide emissions during the critical early season period increased significantly once precipitation occurred in the conventional system (fertilized with urea/eNtrench).
- Green manure termination by blade rolling resulted in the lowest level of nitrous oxide emissions; flail mowing produced intermediate levels while tilling resulted in the highest levels.
- Raising soil N supply biologically did not result in an increase in nitrous oxide emissions.
- The nitrous oxide footprint of organic oats was much lower than that of the conventional oats.
- Green manure termination by blade rolling resulted in the lowest level of nitrous oxide emissions; flail mowing produced intermediate levels while tilling resulted in the highest levels.
Additional Links and Resources
Report (May 2025) Nitrous oxide research results from Glenlea plots (2024-25)
Background Information
From the research activity proposal:
Organic crop production has a more positive greenhouse gas (GHG) footprint than conventional production, where fossil-fuel based N fertilizer accounts for up to 50% of total crop production C emissions. However, questions remain about the soil C storage potential of organic production and the nitrous oxide (N20) emissions associated with organic legume rotation phases. In one of the only Canadian studies to measure GHG emissions in organic production, Westphal et al. (2018) found that, per kg, organic wheat produced 30% less N20 than conventional wheat.
The proposed research will expand our knowledge of GHGs in organic production by measuring N20 emissions and soil C storage for wheat, oat and flax grown in a variety of organic production scenarios. This objective will be achieved through intensive measurements of soil carbon and N20 emissions in a long-term (30 year+) organic experiment located in southern Manitoba; the Glenlea study is the longest running organic field experiment in Canada. One research question regards the status of soil C after 30 years in organic compared with conventional production. How do organic systems compare with conventional systems in terms of soil C sequestration? The long-term study will also be used to address questions of N20 emissions for three major organic grains, wheat, oats and flax. How much N20 is produced in these crops when grown organically compared with the side-by-side conventional treatments under different environmental conditions and in different crop rotations?
Legumes are the backbone of organic grain production since they are the most practical and economical way to add nitrogen. However, legumes can produce N20 upon decomposition. A second major objective is, therefore, to test agronomic management systems aimed at reducing N20 emissions from legumes used in organic farming systems. This research will test different legume-based cover crop systems under different tillage regimes to find the best combination of factors that limit N20 emissions in organic grain production. We will consider both annual legume cover crop systems (eg. peas grown alone or in combination with non-legumes) and perennial alfalfa – an important organic rotation crop for soil improvement and weed control.
The work will be conducted at the University of Manitoba site at Glenlea, where organic farming has been practiced for over 30 years. Conducting the work on a well-established organic farm provides real world application of the results. The site is also part of the National Centre for Livestock in the Environment and hosts many visitors in most years.
Westphal, M, Tenuta, M, Entz, M. 2018. Nitrous oxide emissions with organic crop production depends on fall soil moisture. Agriculture, Ecosystems & Environment, 254:41-49. https://doi.org/10.1016/j.agee.2017.11.005
Contributing Partners
Meet the Research Team
Dr. Michelle Carkner
Dr. Michelle Carkner is an Assistant Professor in Natural Systems Agriculture in the Department of Plant Science at the University of Manitoba, appointed in February 2026. She is an agronomist whose work integrates organic and agroecological cropping-systems research with farmer partnership and on-farm relevance, with particular interest in functional crop diversity, nutrient cycling, and variety improvement for low-input systems.
Dr. Martin Entz, Professor Emeritus
Dr. Martin Entz (now retired) was a professor at the University of Manitoba, where he specialized in Cropping Systems and Natural Systems Agriculture. He founded the university’s Natural Systems Agriculture program, exploring farming inspired by the prairie grasslands and is known for his research in integrating ecology into farming practices. Dr. Entz lead the Glenlea Long-Term Rotation Study, comparing organic and conventional farming systems, and was also part of Sustainable Canada Dialogues, advocating for evidence-based climate solutions. Since 2009, Dr. Entz has been a lead researcher in Organic Science Clusters 1, 2, 3 and 4.
Activity 5 Research Team
Name | Affiliation |
|---|---|
Dr. Mario Tenuta | University of Manitoba |
We asked Dr. Entz
What got you interested in this research project?
The more I learn about climate change, the more alarmed I have become. I am fortunate to be able to help fight climate change by designing and testing agricultural systems that reduce GHG emissions. Also, having a colleague at the UM (Mario Tenuta) with the infrastructure to collect and measure field GHG allows the research to happen.
Where is your research taking place?
At the Glenlea long-term organic vs conventional comparison study, which has been running for 32 years. https://umanitoba.ca/agricultural-food-sciences/long-term-agronomic-studies/glenlea-long-term-rotation
What drew you to organic agriculture research?
I became interested in organic farming at the beginning of my agricultural career. I visited my first organic farm in the 1970’s and I was fascinated by the approach, and that the farmer actually had a flour mill and was selling milled flour.
How are you encouraging or training the next generation of scientists?
I have supervised 50 graduate students in my career with 25 working directly in organic production systems.
Outside of your research pursuits, what is an activity you enjoy doing in your free time?
My favourite outdoor activity is cross country skiing, something that is possible 5 months per year in Manitoba. I also have a small farm and really enjoy trying new organic techniques and practices on my farm.
