Comparing N2O Emissions At Varying N Rates From Rainfed and Irrigated Corn in the US Midwest.

Global N₂O emissions from agriculture are estimated to be ~2.8 Pg CO₂e yr^-1 accounting for 60% of total anthropogenic emissions. N₂O is the largest contributor to the GHG burden of cropping systems in the US, with annual estimated emissions of ~0.5 Tg primarily due to N fertilizer inputs and other soil management activities. Currently 23 million acres of corn, soybean and wheat are irrigated annually in the US with increased N₂O emissions due to the practice likely under-reported in GHG inventories. Here we compare N₂O emissions and yield from irrigated and rainfed corn at varying N rates between 0 and 246 kg N ha^-1 from the Kellogg Biological Station in SW Michigan. Initial results show that N₂O emissions increase with increasing N rate and are significantly higher from irrigated corn compared to rainfed corn at the same N rate. At increasing N rates daily emissions following an irrigation event were between 2.4 – 77.5 g N₂O-N ha^-1 from irrigated corn and 1.6 – 13.0 g N₂O-N ha^-1 from rainfed corn. Emissions data from automated and static chambers will be presented and trade–offs between N₂O emissions, N fertilizer rate, crop yield and irrigation practice will be evaluated from an environmental and economic standpoint.