Nitrous oxide emissions from a cropped soil in a semi-arid climate |
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Authors: | LOUISE BARTON RALF KIESE† DAVID GATTER‡ KLAUS BUTTERBACH-BAHL† RENEE BUCK CHRISTOPH HINZ DANIEL V MURPHY |
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Institution: | School of Earth &Geographical Sciences (M087), Faculty of Natural &Agricultural Sciences, The University of Western Australia, Crawley 6009, Australia,;Karlsruhe Research Centre, Institute for Meteorology &Climate Research, Atmospheric Environmental Research, Garmisch-Partenkirchen, Germany,;The Department of Agriculture &Food Western Australia, Northam, Australia |
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Abstract: | Understanding nitrous oxide (N2O) emissions from agricultural soils in semi‐arid regions is required to better 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 one year on a sub‐daily basis. The site included N‐fertilized (100 kg N ha?1 yr?1) and nonfertilized plots. Emissions were measured using soil chambers connected to a fully automated system that measured N2O using gas chromatography. Daily N2O emissions were low (?1.8 to 7.3 g N2O‐N ha?1 day?1) and culminated in an annual loss of 0.11 kg N2O‐N ha?1 from N‐fertilized soil and 0.09 kg N2O‐N ha?1 from nonfertilized soil. Over half (55%) the annual N2O emission occurred from both N treatments when the soil was fallow, following a series of summer rainfall events. At this time of the year, conditions were conducive for soil microbial N2O production: elevated soil water content, available N, soil temperatures generally >25 °C and no active plant growth. The proportion of N fertilizer emitted as N2O in 1 year, after correction for the ‘background’ emission (no N fertilizer applied), was 0.02%. The emission factor reported in this study was 60 times lower than the IPCC default value for the application of synthetic fertilizers to land (1.25%), suggesting that the default may not be suitable for cropped soils in semi‐arid regions. Applying N fertilizer did not significantly increase the annual N2O emission, demonstrating that a proportion of N2O emitted from agricultural soils may not be directly derived from the application of N fertilizer. ‘Background’ emissions, resulting from other agricultural practices, need to be accounted for if we are to fully assess the impact of agriculture in semi‐arid regions on global terrestrial N2O emissions. |
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Keywords: | Australia CO2 emission factor fallow nitrogen fertilizer rain-fed wheat |
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