Greenhouse Gas Emissions from Drip Irrigated Fields

Abstract. Irrigation practices change the soil moisture in agricultural fields, and in turn influence the emissions of greenhouse gases. A two year field study was conducted to assess the emissions of CO2, and N2O from surface drip and subsurface drip irrigated tomato fields in Southwestern Ontario, Canada. Gas fluxes were obtained through the static chamber method, taking samples every 15 minutes over a one hour time period. Soil moisture and temperature were measured and used to interpret the gas emissions. A peak mean N2O flux at 405 µg m-2 h-1 was observed in the surface drip irrigation treatment on 8 July 2013, following a rainfall event. Most N2O fluxes which occurred during the growing season were around 50 µg N2O-N m-2 h-1 in both treatments. Both the lowest CO2 mean treatment fluxes (12 mg m-2 h-1) and highest (120 mg m-2 h-1) were observed in the surface drip irrigation plots. Seasonal emissions of CO2 were significantly greater in surface drip plots than subsurface drip plots in 2013, but not in 2012, and this is likely attributed to soil temperature differences. Generally, there was no significant difference in soil moisture between the types of drip system. Consequently, there were only a few days which showed significant differences between treatments for the gas fluxes throughout the two growing seasons. Overall, neither subsurface drip irrigation nor surface drip irrigation has a major effect on the emissions of greenhouse gases from the tomato fields in this study.