Greenhouse Gases Emissions and Mitigation from Rice Production Kruamas Smakgahn*, Tamon Fumoto and Kazuyuki Yagi National Institute for Agro-Environmental Sciences National Institute for Agro-Environmental Sciences Tsukuba, Ibaraki, Japan

Contents Background Background Objectives Objectives Introduction to models Introduction to models Results Results Models validation Sensitivity test Conclusions Conclusions

Natural Sources of Atmospheric Methane

Methane is emitted to the atmosphere from wetlands via three primary modes: Methane is emitted to the atmosphere from wetlands via three primary modes: (i) diffusion of dissolved methane across the water- interface, (i) diffusion of dissolved methane across the water- interface, (ii) bubble ebullition, and (ii) bubble ebullition, and (iii) air circulation between the atmosphere and buried tissues of aquatic plants, with the stems and leaves serving as conduits. (iii) air circulation between the atmosphere and buried tissues of aquatic plants, with the stems and leaves serving as conduits. Source: Methane emissions from rice fields.

Nitrous oxide (N 2 O) is a powerful greenhouse gas, about 310 times more effective at trapping heat than carbon dioxide on a molecule-for-molecule basis. Nitrous oxide (N 2 O) is a powerful greenhouse gas, about 310 times more effective at trapping heat than carbon dioxide on a molecule-for-molecule basis. Agricultural activities and animal production systems are the largest anthropogenic sources of these emissions. Agricultural activities and animal production systems are the largest anthropogenic sources of these emissions. N 2 O emissions from agricultural soils occur through the nitrification and denitrification of nitrogen in soils, particularly that from mineral or organic fertilizers. N 2 O emissions from agricultural soils occur through the nitrification and denitrification of nitrogen in soils, particularly that from mineral or organic fertilizers. Emissions are very dependent on local management practices, fertilizer types, and climatic and soil conditions, Emissions are very dependent on local management practices, fertilizer types, and climatic and soil conditions, Natural Sources of Atmospheric N 2 O

Expanding cultivation areas of rice have significantly contributed to the increase in the concentration of atmospheric CH 4 and N 2 O concentration It is difficult to measure emission in large scale and obtain mitigation options, thus model implementation is a promising options for predictions. Objectives To simulate CH 4 and N 2 O emissions from rice fields with varying cultivations practice in different locations in order to consider an accuracy of estimation To obtain mitigation options of CH 4 and N 2 O emissions from rice fields

The process base model: De-Nitrification De-composition model Source: R.A.J. Plant 1998 Source: Fumoto et al. (Submitted GCB) Schematic descriptions of soil Biogeochemistry sub-models

Location of study sites locations of study site in Thailand 1. Rice cultivation under rice straw incorporation (7 sites) Bangkok, Khon Kean, Phrae, Phitsanulok, Sanphatong (Chiang Mai), Suphanburi and Surin province 2. Rice cultivation without rice straw incorporation (2 sites) Samutsakorn and Singburi

soil properties of study sites SiteSoil nameSoil taxonomy Soil texture Carbon (%) Total N (%) Available N (µg N g - 1 ) Free Fe 2 O 3 (g kg -1 ) SO 4 2- (µ g S mL -1 ) Soil pH (flooded) Bangkhen Bangkhen (Bkn) Typic Tropaquepts Heavy clay Khon KaenRoi Et (Et)Aeric Paleaquults Sandy loam0.049 * < 16.8 PhisanulokAlluvial complexLight clay0.14 * PhraeLampang (Lp)Typic Paleaqualfs Silt clay loam * SamutsakornBangkok (Bk)Typic Tropaquepts Clay No data 6.10 San Pa Thong Hang Dong (Hd)Typic Tropaquepts Light clay0.103* SingburiSanphaya (Sp)Aquic Ustifluvents Loam No data 6.90 SuphaburiPhimai (Pm)Vertic Tropaquepts Clay1.30 * SurinRoi Et (Re)Aeric Paleaquults Sandy loam < 16.6

Rice cultivation with rice straw incorporation The revised DNDC model, which is modified by focusing on electron donors presented in soils, yielded appropriated results compared with the original DNDC model

Rice cultivation without rice straw incorporation

Effect of soil properties

The results clearly indicate that the revised DNDC model is highly sensitive to reducible Fe +3 concentration in soil. Less available reducible iron in soil enhances methane emission CH 4 production was suppressed almost completely during ferric iron reductions. Sensitivity test : Fe +3 contents

Soil Clay Contents High clay content in soil or heavy clay texture is trended to mitigated CH 4 emission Low clay content in sandy soil, silt clay soil, silt clay loam are not suitable for CH 4 production predicted by revised DNDC model

Effect of rice straw incorporation

Methane emission under with and without rice straw incorporation Rice cultivation without rice straw incorporation help methane mitigation by %.

-Rice straw incorporated into soil significantly enhanced CH 4 emission. - Correlation between rice straw incorporation and methane emission is linear form Sensitivity tests: Rice straw incorporation

Effect of rice cultivar Rice root biomass directly influences estimation of methane emission - Rice root is a major source of electron donor (DOC) for methane production Rice root

Methane and biomass

Effect of water management

Field drainage Field drainage during growing period (i.e. vegetative, panicle initial, and ripening stage) reduced CH 4 emissions Methane emission was reduced under longer period of field drainage. Methane reduction rate from field drainage in vegetative period is higher than other growth period under the same drainage duration.

Nitrous oxide from different water managements Drainage treatments emitted high N 2 O

Simulated N 2 O from different type of fertilizer applications N2O High N contained fertilizer enhances N2O emission

Conclusions The sensitivity analysis suggested that soil properties such as Fe +3 contents, rice straw incorporation and field drainage are the main factors influence on CH 4 emission The sensitivity analysis suggested that soil properties such as Fe +3 contents, rice straw incorporation and field drainage are the main factors influence on CH 4 emission Field drainage and fertilizer application influence on N 2 O emission Field drainage and fertilizer application influence on N 2 O emission

Mitigation options Possible mitigation options Possible mitigation options 1) Reduce amount of rice straw incorporation into rice soil, 1) Reduce amount of rice straw incorporation into rice soil, 2) conduct field drainage during growing period. 2) conduct field drainage during growing period. However, field drainage may induce weeds and possible to reduce rice grain yield. Therefore, optimum drainage period in optimum growth stage of rice plant needs to concern to obtain the practical mitigation option. 3) Fertilizer application 3) Fertilizer application 4. Rice cultivar 4. Rice cultivar

Acknowledgements This research was funded by the grant of Eco-Frontier Fellowship program by Ministry of the Environment, Japan. This research was funded by the grant of Eco-Frontier Fellowship program by Ministry of the Environment, Japan. We thanks Prof. C.S. Li for DNDC model. We thanks Prof. C.S. Li for DNDC model. Sincere thanks to Prof. Shu Fukai, Dr. Naruo Matsumoto, Dr. Niwat Nadheerong, Mr. Chitnucha Buddhaboon for valuable data and their kindly suggestions on of Thai rice plants characteristics. Sincere thanks to Prof. Shu Fukai, Dr. Naruo Matsumoto, Dr. Niwat Nadheerong, Mr. Chitnucha Buddhaboon for valuable data and their kindly suggestions on of Thai rice plants characteristics.