Determining the Net Greenhouse Gas Budget of Corn Production in Southwestern Ontario Using Long Term Flux Measurements

Corn is widely grown across Southwestern Ontario. The degree to which corn contributes to greenhouse gas emissions is uncertain since annual differences in climatic conditions can affect uptake and release of carbon dioxide (CO₂) to and from the atmosphere as well as nitrous oxide (N₂O) emissions. Long-term, multi-season measurements of CO₂ and N₂O fluxes will help to determine the net greenhouse gas budget (NGB) of corn. Evaluations of NGB require spatially and temporally integrated measurements of all relevant greenhouse gases. The NGB of corn was evaluated using flux measurements of CO₂ and N₂O that were measured continuously for a field in Elora, Ontario, Canada that was under corn production for 9 out of 10 years from 2012 to 2021. CO₂ fluxes were measured using an eddy covariance system and N₂O emissions were measured using a flux-gradient system. The NGB was calculated as the net ecosystem exchange as measured by the EC system plus the carbon removed via harvest and the N₂O emitted per season expressed as CO₂ equivalents. Aside from one season, the NGBs for each growing year showed that the corn was a carbon source. The degree to which the positive NGBs varied from year to year showed no clear correlation with gross primary productivity, respiration, yields, or climatic conditions. This preliminary analysis indicates that although corn production is likely a carbon source, the causes of the carbon production need to be analyzed on shorter time scales, possibly during key periods of growth or respiration, to fully evaluate the drivers that lead to carbon emissions from corn.