Oda Masato, Chiem Nguyen Huu
Crop, Livestock and Environment Division, Japan International Research Center for Agricultural Sciences, Tsukuba, 305-8686, Japan.
Department of Environmental Science, College of Environment and Natural Resources, Can Tho University, Can Tho, Vietnam.
F1000Res. 2018 Aug 29;7:1349. doi: 10.12688/f1000research.15859.3. eCollection 2018.
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. 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. 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. : 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. 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.
在政府间气候变化专门委员会（IPCC）的指南中，水稻被认为会增加稻田的甲烷排放。然而，水稻实际上在甲烷排放方面具有两种相反的作用：一是促进排放，例如通过提供排放途径（通气组织）和产甲烷底物；二是通过提供氧气途径抑制排放，从而抑制甲烷生成或增强甲烷氧化。因此，水稻的总体作用取决于其促进和抑制功能之间的平衡。尽管先前的研究表明水稻会增加甲烷总排放量，但我们旨在在高排放稻田中证明，水稻植株会降低甲烷总排放量。我们比较了越南湄公河三角洲三季稻田中有水稻植株和无水稻植株情况下的甲烷排放。使用气室法采集气体样本，并通过气相色谱法进行分析。我们发现，实际上水稻抑制了高排放稻田中的总体甲烷排放。减排量随着水稻生长至最高分蘖期而增加，抽穗期后减少，最终又恢复。我们的结果表明，甲烷总排放量大于水稻种植面积的排放量。此外，尽管在标准排放稻田中的许多研究发现土壤有机质对甲烷生成的贡献很小，但在高排放稻田中的先前研究表明，甲烷生成主要依赖于过去作物积累的土壤有机质。甲烷排放水平越高，水稻衍生底物的贡献越低；相反，水稻提供氧气的贡献越高。最后，水稻植株减少了高排放稻田中的甲烷排放。本研究表明，在生长季节，水稻抑制了高排放稻田中的甲烷排放。这意味着在高排放稻田中使用具有高抑制性能的水稻品种具有重要意义。
