Growing Green - PulseResearch
April 25, 2017
Research aims to measure the environmental benefits of growing pulses
The carbon dioxide footprint of agricultural products has become an important factor in gaining and maintaining market access. Because of this, it is now critical to be able to accurately determine the magnitude of emissions from crop residues and to understand the controls on these emissions so their overall contribution can be accurately reported. It is also important to be able to identify effective options for mitigating emissions.
This is what Dr. Richard Farrell, an Associate Professor in the College of Agriculture and Bioresources at the University of Saskatchewan (U of S), aimed to do through recently completed research conducted in collaboration with Dr. Diane Knight, a Professor at the U of S, and Dr. Reynald Lemke of Agriculture and Agri-Food Canada.
“The greenhouse gas intensity of agricultural products has become an important criterion for maintaining or gaining market access,” says Dr. Farrell. “Thus, results from this research will help build the case that in addition to agronomic and human health benefits, growing pulses also provides a strong environmental benefit.”
The motivation for this Saskatchewan Pulse Growers (SPG) funded research came from the fact that default emission factors for Western Canada are not necessarily accurate. Research specific to the Western Canadian prairies has shown that the nitrous oxide (N2O) emission factor for nitrogen (N) sources in this region averages about 0.4 to 0.6 per cent. However, the current default emission factor for N sources added to soils is one per cent. “Current procedures for estimating emissions assume that the proportion of nitrogen emitted as nitrous oxide is the same regardless of the nitrogen source, i.e. synthetic fertilizers, animal manures, or the nitrogen crop residues,” Dr. Farrell says. “There is good reason to think that this may not be the case, but not enough evidence to affirm or refute that speculation.”
In order to better determine what these rates should be, Dr. Farrell’s research looked at soils from the Black, Dark Brown, Brown, and Gray Zones with both 50 per cent and 70 per cent water-filled pore space. These soils were amended with 15N-labeled residues of wheat, pea, canola, and flax, and then analyzed for N2O (both total and 15N2O) using a Picarro G5101-i isotopic N2O analyzer – cutting-edge technology that allows for the measurement of the isotopic signature of N2O in the air. One of the major successes of the research was determining that this tool was a relatively simple, low-cost, analytical platform for research of this type.” Having the analytical capacity to detect labelled nitrous oxide provides us with an important tool to identify the source of emissions, thereby providing a better understanding of how nitrogen is being cycled and, hopefully, developing more efficient crop management strategies,” Dr. Farrell says.
Results from the field research showed that, while both water content and soil type had an impact on N2O production, there was a clear and consistent trend showing that emission factors for pea were intermediate compared to other crops researched.
Results also showed that emissions for pulse crops were comparable to cereal crops, which were both quite low in Saskatchewan growing conditions. This information will help support any warranted changes to the Canadian greenhouse gas inventory and the quantity of greenhouse gases assigned to prairie crop production. It will also be useful in helping Saskatchewan pulse growers effectively mitigate their emissions and report them accurately, so that they may avoid marketing risks going forward.
Finally, this information acts as scientific evidence of something that most of us already suspected – that there are environmental benefits to including pulses in your rotation. “Previous work has suggested that overall greenhouse gas emissions are lower from rotations that include pulse crops compared to those that do not, but a number of uncertainties remained – particularly regarding the impact of the pulse residue on nitrous oxide emissions during the following crop year,” Dr. Farrell says. “This work will help to eliminate some of that uncertainty.”
SPG Investment: $77,587
Co-Funders: Ssakatchewan Ministry of Agriculture - Agriculture Development Fund - $67,468
Project Researchers: Dr. Richard Farrell, Associate Professor, College of Agriculture and Bioresources, University of Saskatchewan, Dr. J. Diane Knight, Professor and Ministry of Agriculture Strategic Research Chair, University of Saskatchewan, and Dr. Reynald Lemke, Agriculture and Agri-Food Canada