1. 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

2. Characteristics of agriculture in the study region

3. CH 4 emission from rice fields Measurement sites of CH 4 emission from paddy fields in Asia

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

5. A statistical analysis of factors influencing CH 4 emission Effect Numerator DF Denominator DF F value Pr > F† SOC 1178447.95<.0001 pHpHpHpH7178491.42<.0001 Pre-season water 4178489.55<.0001 Water regime 51784104.74<.0001 Organic amendment 51784116.48<.0001 Climate 6178432.46<.0001

6. Effects of SOC on CH 4 flux 99% confidence

7. Effects of soil pH 99% confidence interval

8. Response of CH 4 emission to difference organic amendment

9. Rice-season water regimes affects CH4 emission 0.360.180.25 Rainfed, dry season 0.370.210.28 Rainfed, wet season 0.800.460.60 Single drainage 0.660.410.52 Multiple drainage 1 Continuously flooded upperlower 95% confidence interval Relative flux Water regime in rice season

10. 0.100.040.06 Two drainages 0.600.460.53 Short drainage 0.420.300.36 Long drainage 1Flooded upperlower 95% confidence interval Relative flux Pre-season water status Off-season water status affects CH 4 emission during rice season

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

12. A conceptional N cycle model

13. Uncertainty caused by timing of rainfall event A Monte Carlo simulation: An upland field, fertilized with 200/150 kg N/ha 1000 runs, assuming 5 rainfall events in a season 5 rainfall events in a season randomly distributed in a season randomly distributed in a season Ratio of N 2 O as a product of nitrification and denitrifcation 20 times higher on raining days than usual Ratio of N 2 O as a product of nitrification and denitrifcation 20 times higher on raining days than usual

14. Relatively well tested mitigation options Nitrification inhibitor Slow release fertilizer Upland 0.72 (n=14) 0.88 (n=13) Paddy 0.73 (n=9) 1.08 (n=3)

15. N dynamic in a upland field

17. Urea: 1 SRF: 0.90 Inhibitor: 0.74

18. Urea: 1 SRF: 1.7 Inhibitor: 0.98 Modeled effects of slow release urea nitrification inhibitor on N 2 O emission from paddy with middle season and end season drainage Nitrification inhibitor Slow release fertilizer Upland 0.72 (n=14) 0.88 (n=13) Paddy 0.73 (n=9) 1.08 (n=3)

19. Conclusions Management practices are more influential than climate and soil properties on CH 4 emission from rice field. Management practices are more influential than climate and soil properties on CH 4 emission from rice field. CH 4 emission can be reduced by appropriate water management and use of organic materials CH 4 emission can be reduced by appropriate water management and use of organic materials N 2 O emission from paddy and NO 3, COM tend to be smaller N 2 O emission from paddy and NO 3, COM tend to be smaller Effects of soil properties, fertilizer and crop type on N 2 O emission can be easily overshadowed by effect of rainfall-induced soil moisture change Effects of soil properties, fertilizer and crop type on N 2 O emission can be easily overshadowed by effect of rainfall-induced soil moisture change Nitrification inhibitors are effective to reduce N 2 O emission from upland, slow release fertilizers are less effective; their effects on paddy depend on water regime Nitrification inhibitors are effective to reduce N 2 O emission from upland, slow release fertilizers are less effective; their effects on paddy depend on water regime