Factors influencing CH4 and N2O emissions from Asian croplands and potential mitigation optionsXiaoyuan YanFrontier Research Center for Global Change, JapanHiroko Akiyama, Kazuyuki YagiNational Institute for Agro-environmental Sciences, Japanyanxy@jamstec.go.jp

Characteristics of agriculture in the study region

Chart2

55.3869087306

15.7747068494

88.7608851834

53.8708957064

% of world total

Sheet1

PopulationLand areaRiceNitrogen fertilizer

Study region55.386908730615.774706849488.760885183453.8708957064

World100100100100

Sheet1

% of world total

Sheet2

Sheet3

Measurement sites of CH4 emission from paddy fields in AsiaCH4 emission from rice fields

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

A statistical analysis of factors influencing CH4 emission

EffectNumerator DFDenominator DFF valuePr > FSOC1178447.95

Effects of SOC on CH4 flux

Effects of soil pH99% confidence interval

Response of CH4 emission to difference organic amendment

Chart2

11111

1.50399523891.09649558271.24099732011.15308590671.3153073903

1.90954103161.15720263731.40806683961.25328089071.5440229245

2.26200167871.20230256281.54007434851.32960710821.730033531

3.14480503371.29513049551.83336121461.4916524552.1584985687

71.31831944921.91122813921.53315121792.2755258888

81.33911794381.98265222481.5707129912.3840067913

91.35800071942.048802051.60509225812.485421209

101.3753115424101.63683987682.5808731989

121.406186977121.69400761752.7571043376

151.4455314526151.76785506212.9930160183

201.4987284251201.86945951743.3327712726

251.5418778087251.953336309525

301.5783451101302.0252322230

351.6100249358353535

401.6380945845404040

451.6633380248454545

Straw_on_season

Compost

Straw_off_season

FYM

GM

Apprication rate of organic materials, t/ha

Relative CH4 flux

solution

SolutionforFixedEffects0.33710.24160.4326

0.40.7342676980.80141541910.6727460434

Standard0.60.84181136850.88389635320.8017301774

EffectEstimateErrorDFt ValuePr>|t|AlphaLowerUpper0.80.92753783660.9475159750.9079809323

1111

Intercept0.3630.263817841.380.1690.05-0.15440.88041.381.21.06338859481.04503344341.0820661393

OC0.33710.0486817846.92

Rice-season water regimes affects CH4 emission0.360.180.25Rainfed, dry season0.370.210.28Rainfed, wet season0.800.460.60Single drainage0.660.410.52Multiple drainage1Continuously floodedupperlower95% confidence intervalRelative flux

Water regime in rice season

Off-season water status affects CH4 emission during rice season

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

A conceptional N cycle model

Uncertainty caused by timing of rainfall event

A Monte Carlo simulation: An upland field, fertilized with 200/150 kg N/ha1000 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

Relatively well tested mitigation options

N dynamic in a upland field

N dynamic in a upland field

N dynamic in a upland fieldUrea: 1SRF: 0.90Inhibitor: 0.74

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

Nitrification inhibitorSlow release fertilizerUpland0.72 (n=14)0.88 (n=13)Paddy0.73 (n=9)1.08 (n=3)

ConclusionsManagement 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

Fo