Organic Science Cluster 4 researchers, Dr. Hiroshi Kubota and his team, are comparing three management systems – conventional tillage, reduced tillage and integrated crop-livestock – for their impact on greenhouse gas (GHG) emissions, carbon sequestration and farm economics during the transition from conventional to organic production.
Agricultural food production is one of the major drivers of global greenhouse gas emissions; in Canada, it contributes about 10 percent of the nation’s total emissions. Organic farming has been reported as more environmentally sustainable due to adoption of organic management practices, including organic crop rotations that incorporate green manure and intercropping, and use of composts and organic soil amendments. Organically managed soils tend to have higher soil organic carbon (SOC), soil organic nitrogen (SON), lower nutrient losses through leaching, increased biological activity and lower compaction and bulk density. A forty-year study conducted by the Rodale Institute also showed that organic farms use 45% less energy compared to conventional farms.
Eliminating tillage operations has had a remarkable impact on the dynamics of soil organic matter. A meta-analysis indicated that no-till practices in conventional cropping systems have increased SOC content by an average of 8.6 per cent in Western Canada since late 1980s. In addition, crop yields have also increased by 7-10 per cent. Since the increased adoption of the no-till practice four decades ago, the Prairie provinces have shifted from a net GHG emission source to a net carbon dioxide (CO2) sink.
Negative effects of intensive tillage are well known to organic field crop producers in Canada. Tillage makes soil more susceptible to erosion, reduces soil organic matter and organism diversity, and increases costs for fuel and labor. However, organic farming has traditionally relied on tillage for termination of green manure crops and management to reduce weed populations.
Plow down and incorporation of green manure biomass into the soil is the most effective method for fast mineralization and release of nutrients to crops that follow. Various tillage methods are used throughout the growing season, such as spring cultivation to prepare the seedbeds, tine harrow and rotary hoe to remove early germinated weeds, in-crop cultivation to control late developed weeds, and fall tillage to suppress perennial weeds.
Complete elimination of tillage operations on organic farms is currently not realistic. However, reducing tillage intensity can be implemented, particularly in the year of a green manure crop when alternative termination methods are used. A full season multispecies green manure crop provides opportunities for incorporating intensive livestock grazing for periods of time. Green manure crops can be terminated with a roller crimper or mower to leave a layer of mulch on the soil surface to offer soil protection, weed suppression, and allow for direct seeding with no tillage the next spring.
Reducing tillage intensity lessens disturbance of soil structure and slows down the decomposition rate of soil organic matter, thereby increasing SOC content. Research in Europe found that after 12 years of minimum tillage, the SOC in the top 10 cm of soil increased by 21 per cent (from 1.60% to 1.94%) in operations under organic management, while it decreased from 1.45% to 1.36% in soils where conventional tillage was used.
Another study also found that reduced tillage over a six-year period increased SOC in the top 10-cm by 19 per cent (from 2.19% to 2.61%) and the SOC below this depth remained unchanged or reduced slightly. Crop yields decreased by an average of seven per cent in the first three years, but the following forage crop yields increased by 29 per cent. In Lethbridge Alberta, organic producers have successfully terminated the cover crops with roller-crimpers, maintained weeds under control, and used direct seed drills to plant the following year crops without a tillage operation.
Integrating livestock requires a system change so that additional benefits can be achieved through circularity of nutrients and feed products for crop production. Livestock enhances on-farm recycling of soil nutrients, diversifies incomes and reduces costs for forage harvest and manure transport. Livestock deposit manure while grazing, increasing soil organic matter, growing soil microbial activities and strengthening biological cycling of nutrients. Managing weeds with intensive grazing has been successful on many organic farms.
Soil-borne GHGs include CO2, nitrous oxide (N2O) and methane (CH4). N2O is produced as a byproduct during denitrification, a microbial conversion of nitrate (NO3-1) to N2 gas, when soil has limited oxygen availability. A comparison study in Manitoba showed that average N2O emissions from organic alfalfa-wheat rotation account for 34 per cent of the emissions from soybean-wheat rotation in conventional systems. The majority of agricultural CH4 emissions come from beef and dairy cattle and manure management systems.
The Canadian Prairies are home to approximately1,596,300 acres certified organic lands, which account for 54.7 per cent of the nation’s total in 2023. About 65 per cent of these lands are dedicated to growing field crops including cereals (wheat, oat, barley, and rye), pulses (lentil and pea), and oilseeds (flax, mustard, and hemp). Prairie organic producers are seeking new approaches to improve their cropping system efficiency and adapt to climate changes. Reducing tillage operations and integrating livestock in crop production are two management practices that producers have recently been interested in. However, limited research and information is available on the effects of these practices on soil health, environmental benefits, and the impact on crop production and farm economics. Several studies either exhibit inconsistent conclusions or are not applicable to the Prairie soil-environmental conditions. The Canada GHG Offset Credit System supports farming practices that reduce GHG emissions or increase carbon sequestration to qualify for federal GHG credits and the credits can participate in carbon marketing. This program is designed to encourage producers to implement different management practices.
At Agriculture and Agri-Food Canada (AAFC), Lacombe Research Development Center, Alberta, Dr. Hiroshi Kubota and his team are conducting research that compares N2O emissions and soil carbon sequestration of three management systems: conventional tillage, reduced tillage and integrated crop-livestock during the transitional period from conventional cropping systems to organic production.
This research will identify cropping systems that perform better in terms of reduction of GHG emissions, increase soil carbon sequestration, suppress weeds, enhance biological cycling of soil nutrients, and improve crop yields through both small-plot and on-farm trials. Research will also analyze soil quality indicators, crop production markers and farming economics to promote the best practices for both environmental and economical sustainability.
Although this research has just started and no experimental results are available yet, it is expected that this project will generate useful data that will fill identified knowledge gaps and provide strong scientific support to sustainable farming practices for organic crop production on the Canadian Prairies.
Published February 10, 2025
Organic Science Cluster 4 is an industry-led research and development endeavour co-managed by the Organic Federation of Canada and the Organic Agriculture Centre of Canada at Dalhousie University and supported by the AgriScience Program under Agriculture and Agri-Food Canada’s Sustainable Canadian Agricultural Partnership together with over 80 funding partners.
