Mitigating N2O emissions from cropping systems after conversion from pasture ? a modelling approach |
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| Institution: | 1. Scotland''s Rural College (SRUC), Kings Buildings, West Mains Road, Edinburgh EH9 3JG, UK;2. ADAS Boxworth, Cambridge CB23 4NN, UK;3. Rothamsted Research, North Wyke, Devon EX20 2SB, UK;4. School of Environment, Natural Resources and Geography, Bangor University, Bangor LL57 2UW, UK;1. Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research (IMK-IFU), Kreuzeckbahnstr. 19, 82467 Garmisch-Partenkirchen, Germany;2. Leibniz Centre for Agriculture Landscape Research (ZALF) e.V., Institute for Landscape Biogeochemistry, Eberswalder Str. 84, 15374 Müncheberg, Germany;3. Istituto per i Sistemi Agricoli e Forestali del Mediterraneo CNR, Via C. Patacca 85, 80056 Ercolano, Napoli, Italy;4. Center for the Study of the Biosphere from Space (CESBIO),Unité mixte de recherché (UPS, CNRS, CNES, IRD), Toulouse, France;5. Agroscope Reckenholz-Tänikon ART, Swiss Federal Research Station, Reckenholzstrasse 191, CH-8046 Zürich, Switzerland;6. INRA, AgroParisTech, UMR, 1091 EGC, Environnement et Grandes Cultures, 78850 Thiverval-Grignon, France;7. Centre of Ecology & Hydrology (CEH), Edinburgh, Bush Estate, Penicuik, Midlothian EH26 QB, United Kingdom;8. Scotland''s Rural College (SRUC), Crop & Soils Systems, Peter Wilson Building, Kings Buildings, West Mains Road, Edinburgh EH9 3JG, United Kingdom;9. Thünen Institut, Institut für Agrarklimaschutz, Bundesallee 50, 38116 Braunschweig, Germany;1. College of Resources and Environment, Huazhong Agricultural University, Wuhan 43070, China;2. Department of Soil Science, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan |
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| Abstract: | Converting pasture to cropping is common in many of the world’s agricultural systems. This conversion results in substantial net mineralisation of soil organic matter that builds up during a phase of pasture. A few studies have shown that this mineralisation leads to increased nitrous oxide (N2O) emissions compared to long-term pasture or long-term cropping. Understanding of interactions leading to these significant emissions is still scarce but is needed to identify mitigation options for this situation. In this study, the Agricultural Production Systems sIMulator (APSIM) was used to investigate the optimal timing of pasture termination (relative to crop planting) and management of nitrogen (N) in crops after pasture termination to maximise crop yield and limit N2O emissions. Beforehand, APSIM’s performance in simulating yields and N2O emissions was tested against data from field experiments conducted in the temperate high-rainfall zone of southern Australia where N2O emissions were monitored with automatic gas collection chambers during the first year of cropping wheat after terminating long-term pasture on two adjacent sites in two consecutive years. Field experiments and simulation scenarios showed very high N2O emissions (up to 48 kg N2O-N ha?1 yr?1) in the first year of wheat after pasture termination, even without N fertiliser application. Measured cumulative N2O emissions, crop yields and soil mineral N and water content dynamics were simulated well with APSIM. Including a routine into APSIM to account for N2O transport through the soil profile improved the simulation of daily N2O emissions considerably, leading to up to 67% of the measured variability in daily N2O emissions being explained by the model. We predicted that a short fallow between termination of pasture and sowing wheat, instead of a long fallow which is the common practice, reduces N2O emissions by more than half in the first year of cropping without a noteworthy impact on crop yield. Reducing N fertiliser applications in the first few years after pasture termination by taking available soil mineral N into account, and applying the fertiliser six to twelve weeks after sowing instead of at sowing was predicted to further reduce N2O emissions. Since the model was calibrated against experimental data during the first year after pasture termination only, experiments determining N2O emissions in the first two or three years after terminating pasture are needed to confirm our predictions. |
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| Keywords: | Land-use change Pasture termination Nitrous oxide APSIM Mitigation |
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