See more from this Session: Virtual Posters
Sunday, October 31, 2010
Long Beach Convention Center, Outside Room 204, Second Floor, Virtual Posters
Nitrous oxide (N2O) emissions from rain-fed agricultural soils in semi-arid regions have rarely been reported, but are required to understand global terrestrial N2O losses. Nitrous oxide emissions were measured from a rain-fed, cropped soil in a semi-arid region of south-western Australia for three years on a sub-daily basis. The site included N fertilizer (75–100 kg N ha-1 yr-1) and no N fertilizer plots (control). Emissions were measured using soil chambers connected to a fully automated system that measured N2O using gas chromatography. Daily N2O emissions were low (-2.1–7.3 g N2O-N ha-1 day-1) and culminated in 0.09–0.13 kg N2O-N ha-1 yr-1 from the N fertilized soil and 0.07–0.09 kg N2O-N ha-1 yr-1 from the control. The proportion of N fertilizer emitted as N2O each year, after correction for the control fluxes, was 0.02–0.06%. The emission factor in the present study was up to 50 times lower than the IPCC default value for the application of synthetic fertilizers to land (1.0%), indicating the default value may not be suitable for cropped soils in semi-arid regions. Daily N2O emissions did not increase immediately in response N fertilizer applications. Furthermore in the first year, over half (55%) the annual N2O emission occurred from both N fertilizer treatments following a series of summer rainfall events while the soil was fallow (i.e., no active plant growth). The timing of N2O emissions suggests modifying N fertilizer practices are unlikely to decrease N2O emissions from rain-fed, cropped soils in our region.