Greenhouse Gas Intensity of a Typical Irrigated Cropping System in the Semi-Arid Prairie Region.

Driven by increasing global food demands, the proportion of irrigated agriculture within the Canadian Prairies is likely to increase. However, the implications of this with respect to the agricultural greenhouse gas (GHG) balance are not well understood.  This study investigates and compares the greenhouse gas intensity of a typical irrigated and dryland cropping system in Saskatchewan, a semi-arid region of the Canadian Prairies.  Irrigated cropping systems contribute greater GHG emissions than their dryland counterpart due to larger nitrous oxide (N₂O) production rates and energy used for irrigation water delivery.  Yet, partial offsets may be achieved through increases in soil carbon storage from the greater productivity realized through irrigation.  Chamber-based flux measurements have been employed to quantify soil GHG emissions and the factors driving these emissions have been investigated through in-situ soil temperature, matric potential, and moisture measurements.  The emissions associated with pumping water and typical crop management activities are accounted for using the Intergovernmental Panel on Climate Change (IPCC) literature and methodology.  Results from two seasons of study will be presented.  Preliminary results from the 2012 season confirm that irrigated cropping systems have greater greenhouse gas intensity, largely due to soil N₂O emissions. Soil N₂O emissions from the irrigated system were four times greater than the dryland and were the greatest source of emissions for that system.  Emissions associated with pumping were notable; however, due to the wet growing season they remained smaller than could be expected most years.  Diesel combustion used to power equipment was comparable between cropping systems.  The information derived from this study will aid in the development of regional specific soil emission factors, improved management strategies, and will identify areas of focus for mitigation efforts.