College of Resources and Environment, Huazhong Agricultural University, Wuhan 43070, China.
College of Resources and Environment, Huazhong Agricultural University, Wuhan 43070, China; Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China.
Sci Total Environ. 2022 Oct 10;842:156781. doi: 10.1016/j.scitotenv.2022.156781. Epub 2022 Jun 18.
Appropriate crop rotation in rice field is an important measure to maintain soil fertility and rice productivity. However, the effects of different rice rotation systems on methane (CH) emission and the underlying mechanisms, as well as rice grain yields have not been well assessed. Here, a 2-year field study involving three rice rotation systems (Wh-PR: wheat-flooded rice rotation, Ra-PR: rapeseed-flooded rice rotation, Ra-UR: rapeseed-aerobic rice rotation) was conducted. CH emissions, methanogenic and methanotrophic communities and rice grain yields were measured during rice growing seasons to determine which rice rotation pattern can reduce CH emissions and improve rice grain yields. The average cumulative CH emission was 136.19 kg C ha in Ra-PR system, which was significantly higher than that in Wh-PR and Ra-UR systems by 60.6 % and 14.6-fold, respectively. These results were mainly attributed to the low soil dissolved organic carbon in Wh-PR system and the well aerated soil condition in Ra-UR system, as compared with Ra-PR system. Rice grain yields exhibited no significant differences among the three rotation systems in 2019 and 2020. The abundances of methanogens in Ra-PR system were obviously higher than those in Wh-PR and Ra-UR systems. While the abundances of methanotrophs were comparable between Ra-PR and Wh-PR systems, which exhibited significantly lower abundances than that in Ra-UR system. CH fluxes showed markedly positive relations to the abundances of methanogens, while exhibited no relationship with the abundances of methanotrophs. Both methanogenic and methanotrophic community compositions differed considerably in Wh-PR and Ra-UR systems in comparison with Ra-PR system. Specifically, the relative low abundances of Methanothrix and Type I methanotrophs occurred in Wh-PR and Ra-UR systems, whereas Methanosarcina, Methanocella, Methanomassiliicoccus and type II methanotrophs (Methylocystis and Methylosinus) were found in higher relative abundances in Wh-PR and Ra-UR systems. Overall, changing the preceding upland crop types or introducing aerobic rice to substitute flooded rice in rice-based rotation systems could diminish CH emissions, mainly by regulating soil properties and eventually changing soil methanogenic and methanotrophic communities.
稻田合理轮作是维持土壤肥力和水稻生产力的重要措施。然而，不同的水稻轮作系统对甲烷（CH）排放的影响及其潜在机制，以及水稻籽粒产量尚未得到很好的评估。在这里，进行了一项为期两年的田间研究，涉及三种水稻轮作系统（Wh-PR：小麦淹水轮作，Ra-PR：油菜淹水轮作，Ra-UR：油菜好气轮作）。在水稻生长季节测量 CH 排放、产甲烷菌和甲烷氧化菌群落和水稻籽粒产量，以确定哪种水稻轮作模式可以减少 CH 排放并提高水稻籽粒产量。Ra-PR 系统的平均累积 CH 排放量为 136.19kg C ha-1，比 Wh-PR 和 Ra-UR 系统分别高 60.6%和 14.6 倍。这些结果主要归因于 Wh-PR 系统中土壤溶解性有机碳较低和 Ra-UR 系统中土壤通气条件良好，而与 Ra-PR 系统相比。2019 年和 2020 年，三种轮作系统的水稻籽粒产量无显著差异。Ra-PR 系统中产甲烷菌的丰度明显高于 Wh-PR 和 Ra-UR 系统。而 Ra-PR 和 Wh-PR 系统中产甲烷菌的丰度相当，明显低于 Ra-UR 系统。CH 通量与产甲烷菌的丰度呈显著正相关，而与甲烷氧化菌的丰度无关。与 Ra-PR 系统相比，Wh-PR 和 Ra-UR 系统的产甲烷菌和甲烷氧化菌群落组成差异较大。具体而言，Wh-PR 和 Ra-UR 系统中产甲烷菌的相对丰度较低，而 Methanosarcina、Methanocella、Methanomassiliicoccus 和 II 型甲烷氧化菌（Methylocystis 和 Methylosinus）的相对丰度较高。总的来说，改变前茬旱地作物类型或引入好气水稻替代水稻轮作系统中的淹水水稻，可以减少 CH 排放，主要是通过调节土壤性质，最终改变土壤产甲烷菌和甲烷氧化菌群落。
