Bert Tanner Student Presentation Award
Rebecca Johnson, University of Guelph
How does Soil Type, Crop Rotation Diversity and Climate Change affect Freeze-Thaw Nitrous Oxide Emissions?
The bracketed numbers in the synopsis below refer to each slide in the presentation, download it here:
Nitrous Oxide (N2O) is a trace greenhouse gas that contributes to atmospheric warming and stratospheric ozone depletion (1). In Canada, 49% of agricultural greenhouse gas emissions are from N2O production where a large majority of that occurs on agricultural soils. In cold climates, N2O can be emitted throughout the winter periods from freeze-thaw processes which can contribute large proportions to the annual N2O emissions on a field. However, these emissions vary based on soil type, climate and crop management (2). Sustainable or “climate-smart” practices like cover crop use and crop rotation diversification provide many benefits to soil health, but the effects to freeze-thaw N2O production are not well understood. How will these crop management strategies impact freeze-thaw N2O production under climate change?
This research was conducted at the University of Guelph Elora Research Station where large monolithic weighing lysimeters are used to study two soil types, sandy loam and silt loam, under the same weather conditions (3). The 18 lysimeters undergo one of three crop rotation treatments: simple, diverse or diverse with winter warming (5/6). On top of each lysimeter, automatic flux chambers monitor N2O production and are attached to a tunable diode laser trace-gas analyzer (4). Data presented represents the freeze-thaw period in the spring of 2019, from February 15 to April 15 (7-8).
Preliminary results show a large freeze-thaw emission event which occurred around March 15, 2019. Environmental conditions show an increase in air and soil temperature, which led to snow melt and an increase in volumetric water content (7). During the emission event, N2O production was observed in the simple and diverse treatments with silt loam soils, with small emissions from the sandy loam diverse rotation (8). Warmed treatments under both soil types showed low N2O emissions. Total emissions throughout the freeze-thaw period show different trends, however, statistical analysis is still necessary to quantify these differences (9).