Greenhouse gas exchange over a conventionally managed highbush blueberry field in the Lower Fraser Valley in British Columbia, Canada

Agricultural fields can be significant sources of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4), with implications for climate change. This paper reports continuous half-hourly CO2, CH4 and N2O fluxes over a conventionally-managed highbush blueberry field on Westham Island in Delta, British Columbia (BC), Canada, measured using the eddy-covariance (EC) method for a 1-year period. Field management, including fertilization and mowing interrow grass, was associated with substantial changes in GHG exchange. With emissions of N2O and CH4 totaling 0.61 +/- 0.03 g N2O m(-2) year(-1) and 0.81 +/- 0.4 g CH4 m(-2) year(-1), corresponding to 182 +/- 9 g and 30 +/- 13 g CO2 equivalent (CO(2)e) m year(-1), respectively, based on their 100-year global warming potentials, the field was a net source of 840 +/- 126 g CO(2)e m(-2) year(-1). The annual net ecosystem exchange of CO2 (NEEc) was the largest component of the GHG balance at 171 +/- 28 g C m(-2) year(-1) (628 +/- 104 g CO2 m(-2) year(-1)), indicating the field was a net carbon (C) source. After accounting for inputs and outputs of C in sawdust and harvested fruit, respectively, the agroecosystem gained a net of 233 +/- 88 g C m(-2) year(-1), primarily controlled by the application of sawdust mulch. Both soil temperature and soil moisture were important environmental factors controlling GHG emissions, which has implications for future feedback cycles and climate change. Our results suggest that agricultural management strategies can be targeted for GHG mitigation.