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Real-life carbon data

A project is underway to provide a much more comprehensive, in-field evaluation of the net carbon balance of a Saskatchewan cropping system than ever before available. The results could help Saskatchewan crop growers in key ways.

“Canada’s ambitious target to reduce its greenhouse gas emissions 40 to 45 per cent below 2005 levels by 2030 will continue to drive environmental policy initiatives and will impact agriculture. Having carbon footprint data for crop production in Saskatchewan will be very important to help our farmers tell their sustainability story and help shape future policies that recognize farmers’ environmental conservation efforts,” explains Blair Goldade, executive director of the Saskatchewan Wheat Development Commission (Sask Wheat), one of the project’s funding organizations.

He notes, “Grain producers have already been reducing greenhouse gas emissions for decades with their no-till and continuous cropping practices, which sequester [store] carbon into the soil.” The project’s results could assist policymakers in comparing cropping regions, perhaps confirming preliminary data indicating that Saskatchewan cropping systems may have a relatively small carbon footprint.

In addition, the project could provide growers with valuable information on nitrogen fertilizer options that increase the efficiency of nitrogen applications by reducing nitrogen losses to the environment. Goldade says, “Data like this will help producers make better fertilizer decisions where they can see some savings while also maintaining their yields and profits.”

Along with Sask Wheat, the project is funded by the Saskatchewan Oat Development Commission, Saskatchewan Canola Development Commission, and the Saskatchewan Ministry of Agriculture through the Saskatchewan Agriculture Development Fund (ADF). The ADF is supported through the federal-provincial Canadian Agricultural Partnership.

Direct, in-field measurements

“The goal of this project is to provide direct, year-round and field-scale greenhouse gas emission measurements for a representative cropping system in Saskatchewan,” says Kate Congreves, an assistant professor at the University of Saskatchewan (USask) who is leading the project.

Congreves explains that a lot of the current information on the carbon footprint of soil and cropping systems is based on various carbon models. However, some of the assumptions used in those models might not be perfect for accurately predicting greenhouse gas emissions in Saskatchewan fields.

“Some preliminary results from recent Saskatchewan studies have shown fairly low emissions at spring thaw. Spring thaw is a period when we normally get high greenhouse gas emissions. Spring thaw periods can contribute a major chunk of annual greenhouse gas emissions; so, if we’re seeing medium to low emissions at thaw, then it might point toward a lower footprint here,” she says.

“However, we don’t know for sure. That’s why we have set out to measure the greenhouse gas emissions at thaw and throughout the whole year, and all the other factors that go into the overall carbon footprint. It is also why we want to measure emissions over multiple years.”

A crucial factor in making these measurements possible is the advanced “flux gradient” micrometeorology equipment at the project’s study site in a field at the university in Saskatoon.

The flux gradient monitoring system involves several towers with devices that track the ongoing fluctuations in the amounts of nitrous oxide (N₂O) and carbon dioxide (CO₂), near-continuously, all year long, across the 11-hectare study site.

Congreves notes that nitrous oxide is a potent greenhouse gas with a more powerful greenhouse warming potential than carbon dioxide. But both greenhouse gases are very important in Prairie crop production systems. Nitrous oxide is emitted from the soil, especially at spring thaw, and after nitrogen fertilizer applications. Carbon dioxide is emitted from soil decomposition and plant respiration as the crop grows. However, carbon dioxide is also taken up by plants and sequestered in the soil.

“So, we want to know: how much greenhouse gas are we losing versus how much are we sequestering? What is the balance? Is this a net source or a net sink?” she says.

The flux gradient system is more convenient and accurate than the usual method of measuring greenhouse gases in fields, which involves placing little chambers across the soil surface to collect gas samples. Because greenhouse gas emissions can really vary across a field, you have to put many of these chambers in the field to try to capture all that variability.

Also, those chambers just measure the soil-derived gas emissions, whereas the flux gradient system monitors the soil-plant system, providing measurements on the balance between how much is emitted and how much is sequestered. That way, the researchers can put together the whole picture of the field’s net carbon footprint.

Another advantage of the flux gradient system is that it automatically collects data all the time – including when field conditions would make it difficult for a person to collect the measurements and when the emissions are rapidly changing, like at the start of spring melt.

The flux gradient equipment is on loan to Congreves’ group from Claudia Wagner-Riddle at the University of Guelph. Wagner-Riddle is one of the project’s collaborating researchers, along with Rich Farrell, Warren Helgason and Tristan Skolrud at USask, and Shannon Brown at the University of Guelph.

Congreves’ project team is supplementing the flux gradient monitoring with many other types of data collection such as soil sampling, plant sampling, soil moisture monitoring, and soil temperature monitoring. They get weather data courtesy of the Saskatchewan Research Council’s meteorological station at the study site.

The representative cropping system in this project is a two-year canola-wheat rotation in a no-till system. The team is tracking the net greenhouse gas emissions of this cropping system for four years and several nitrogen fertilizer options.

They are comparing different nitrogen rates – recommended rates, soil-test rates and reduced rates, and different nitrogen sources – the conventional source (urea) and an enhanced efficiency nitrogen fertilizer product.

The field experiment started in 2021 with the first canola year of the rotation. Like much of Saskatchewan, they experienced issues due to drought last summer, and they are hoping for better weather in 2022.

A win-win

Congreves points out that the net carbon footprint information from the project could be extremely useful for crop growers. For example, if the results show certain management practices or systems are better at creating carbon sinks, then that could help improve the sustainability of agriculture, save money on fertilizer inputs, and perhaps open up opportunities for carbon credits for Saskatchewan crop growers someday.

“Sask Wheat and other farm organizations continue to advocate for producers to be recognized and compensated for the carbon they sequester and the environmental conservation efforts they participate in. Projects like this will help accomplish this objective. We are also investing in projects that are looking at similar areas with regard to emission reductions and quantifiable datasets that will help direct policy,” notes Goldade. “We want sound policies developed based on science and sound data.”

He adds, “Nitrogen use efficiency has been studied significantly over the past decade or so. If the data from this project can further contribute to more efficient nitrogen applications that maintain crop yields while reducing nitrous oxide emissions and nitrogen runoff, then producers and ultimately consumers will benefit on two fronts: costs and the environmental impact. So, it’s a win-win.”