Dataset Information

Methane emissions in triple rice cropping: patterns and a method for reduction.

ABSTRACT: The Mekong Delta paddies are known as hotspots of methane emission, but these emissions are not well studied. We analyzed methane emission patterns based on monitoring data from typical triple rice cropping paddies collected over 5 years. We found that the total emissions in a crop season doubled in the second crop, tripled in the third crop, and reset after the annual natural flood of the Mekong River. The emission peaks occurred around 0 to 3 weeks after starting irrigation, then gradually decreased. This suggests that methane was generated by the soil organic matter, because the small rice plants provide little carbon for methanogenesis. In general, the main source of emitted methane is rice-derived carbon by current-season photosynthates and the emission peaks at the rice heading stage. However, the contribution of the rice-derived carbon is negligible in the hotspot paddies while total emission is high. The increase in emission levels from the first to the third crop can be explained by the accumulation of rice residue from the preceding crops, especially rice straw incorporated into the soil. The reset of emission levels after annual flood means that the rice straw is decomposed without methanogenesis in water with dissolved oxygen. Thus, the annual emission pattern shows that decomposing rice straw in paddy surface-water is an effective method to reduce methane emissions.

SUBMITTER: Oda M

PROVIDER: S-EPMC7059783 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Methane emissions in triple rice cropping: patterns and a method for reduction.

Oda Masato M Nguyen Huu Chiem HC

F1000Research 20190923

The Mekong Delta paddies are known as hotspots of methane emission, but these emissions are not well studied. We analyzed methane emission patterns based on monitoring data from typical triple rice cropping paddies collected over 5 years. We found that the total emissions in a crop season doubled in the second crop, tripled in the third crop, and reset after the annual natural flood of the Mekong River. The emission peaks occurred around 0 to 3 weeks after starting irrigation, then gradually dec ...[more]

PMID: 32185020

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Project description:Background: Rice is understood to enhance methane emissions from paddy fields in IPCC guidelines. However, rice actually has two opposite functions related to methane: i) emission enhancement, such as by providing emission pathways (aerenchyma) and methanogenetic substrates; and ii) emission suppression by providing oxygen pathways, which suppress methanogenesis or enhance methane oxidation. The overall role of rice is thus determined by the balance between its enhancing and suppressing functions. Although previous studies have suggested that rice enhances total methane emissions, we aimed to demonstrate in high-emitting paddy fields that the overall methane emission is decreased by rice plants. Methods: We compared methane emissions with and without rice plants in triple cropping rice paddy fields in the Mekong Delta, Vietnam. The gas samples are collected using chamber method and ware analyzed by gas chromatography. Results: We found that rice, in fact, suppressed overall methane emissions in high-emitting paddies. The emission reductions increased with the growth of rice to the maximum tillering stage, then decreased after the heading stage, and finally recovered. Discussion: Our result indicates that the overall methane emission is larger than that of rice planted area. In addition, although many studies in standard-emitting paddies have found that the contribution of soil organic matter to methanogenesis is small, prior studies in high-emitting paddies suggest that methanogenesis depended mainly on soil organic matter accumulated from past crops. The higher the methane emission level, the lower the contribution of the rice-derived substrate; conversely, the higher the contribution of the rice providing oxygen. Finally, rice plants reduce methane emissions in high-emitting paddies. Conclusion: The present study demonstrates that during the growing season, rice is suppressing methane emissions in high-emitting paddies. This means the significance of using the rice variety which has high suppressing performance in high-emitting paddies.

Project description:Paddy rice fields are one of the most important sources of anthropogenic methane. Improving the accuracy in the CH4 budget is fundamental to identify strategies to mitigate climate change. Such improvement requires a mechanistic understanding of the complex interactions between environmental and agronomic factors determining CH4 emissions, and also the characterization of the annual temporal CH4 emissions pattern in the whole crop cycle. Hence, both the growing and fallow seasons must be included. However, most of the previous research has been based on single-factor analyses that are focused on the growing season. In order to fill this gap, a study was conducted in a Mediterranean rice agrosystem (Ebre Delta, Catalonia) following a farm-to-farm approach with the purpose of 1) evaluating the cumulative and temporal pattern of CH4 emission, and 2) conducting a multi-variate analyses to assess the associative pattern, relative contribution and temporal variation of the main explanatory variables concerning the observed CH4 emissions. Measurements of CH4 emissions and agronomic and environmental parameters in 15 commercial rice fields were monitored monthly, during a whole crop field cycle. The temporal pattern of CH4 emission followed a bi-modal distribution peaking in August and October. The cumulative annual CH4 emissions from rice fields amounted 314 kg CH4 kg ha-1, of which ca. 70% were emitted during the fallow season. The main controlling factors of the CH4 emission rate in the growing season were positive related to water level and plant cover, while soil redox was negatively related. The main controlling factors in the fallow season were water level (negatively related, conversely to the growing season), as well as straw incorporation and soil temperature (positively related). The results of this study highlight the importance of the often neglected fallow season in the accurate estimation of CH4 emissions and, thus, the necessity of measurement programs that cover the whole crop field cycle. This information is the first step for setting effective mitigation strategies based on straw and water management.

Dataset Information

Methane emissions in triple rice cropping: patterns and a method for reduction.

Publications

Methane emissions in triple rice cropping: patterns and a method for reduction.

Similar Datasets

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