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Xiaoyuan Yan Frontier Research Center for Global Change, Japan Hiroko Akiyama, Kazuyuki Yagi

Factors influencing CH 4 and N 2 O emissions from Asian croplands and potential mitigation options. Xiaoyuan Yan Frontier Research Center for Global Change, Japan Hiroko Akiyama, Kazuyuki Yagi National Institute for Agro-environmental Sciences, Japan yanxy@jamstec.go.jp.

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Xiaoyuan Yan Frontier Research Center for Global Change, Japan Hiroko Akiyama, Kazuyuki Yagi

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  1. Factors influencing CH4 and N2O emissions from Asian croplands and potential mitigation options Xiaoyuan Yan Frontier Research Center for Global Change, Japan Hiroko Akiyama, Kazuyuki Yagi National Institute for Agro-environmental Sciences, Japan yanxy@jamstec.go.jp

  2. Characteristics of agriculture in the study region

  3. Measurement sites of CH4 emission from paddy fields in Asia CH4 emission from rice fields

  4. Statistical analysis: A linear mixed model Fixed effects: soil properties (SOC, pH) climate water status before rice season water regime during rice season type and amount of organic fertilizer Random effect: paper

  5. A statistical analysis of factors influencing CH4 emission

  6. 99% confidence Effects of SOC on CH4 flux

  7. Effects of soil pH 99% confidence interval

  8. Response of CH4 emission to difference organic amendment

  9. Rice-season water regimes affects CH4 emission Water regime in rice season Relative flux 95% confidence interval lower upper Continuously flooded 1 Multiple drainage 0.52 0.41 0.66 Single drainage 0.60 0.46 0.80 Rainfed, wet season 0.28 0.21 0.37 Rainfed, dry season 0.25 0.18 0.36

  10. Pre-season water status Relative flux 95% confidence interval lower upper Flooded 1 Long drainage 0.36 0.30 0.42 Short drainage 0.53 0.46 0.60 Two drainages 0.06 0.04 0.10 Off-season water status affects CH4 emission during rice season

  11. Field measurement data of N2O from croplands in Asian: A Statistical analysis Fixed effects: soil properties crop type chemical N type and amount mitigation option Random effect: paper

  12. A conceptional N cycle model

  13. Uncertainty caused by timing of rainfall event A Monte Carlo simulation: An upland field, fertilizedwith 200/150 kg N/ha 1000 runs, assuming • 5 rainfall events in a season • randomly distributed in a season • Ratio of N2O as a product of nitrification and denitrifcation 20 times higher on raining days than usual

  14. Relatively well tested mitigation options

  15. N dynamic in a upland field

  16. N dynamic in a upland field

  17. N dynamic in a upland field Urea: 1 SRF: 0.90 Inhibitor: 0.74

  18. Modeled effects of slow release urea nitrification inhibitor on N2O emission from paddy with middle season and end season drainage Urea: 1 SRF: 1.7 Inhibitor: 0.98

  19. Conclusions • Management practices are more influential than climate and soil properties on CH4 emission from rice field. • CH4 emission can be reduced by appropriate water management and use of organic materials • N2O emission from paddy and NO3, COM tend to be smaller • Effects of soil properties, fertilizer and crop type on N2O emission can be easily overshadowed by effect of rainfall-induced soil moisture change • Nitrification inhibitors are effective to reduce N2O emission from upland, slow release fertilizers are less effective; their effects on paddy depend on water regime

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