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| Methane emission and the effecting factors in rice-fish system |
| Received:January 23, 2025 |
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| KeyWord:rice-fish system;methane emission;rice yield;fish yield;fish stocking density;fish feed;simulated fish activity |
| Author Name | Affiliation | E-mail | | FAN Dongdong | College of Life Sciences, Zhejiang University, Hangzhou 310058, China | | | HU Liangliang | College of Life Sciences, Zhejiang University, Hangzhou 310058, China | | | ZHAO Lufeng | College of Life Sciences, Zhejiang University, Hangzhou 310058, China
Zhejiang University-Lishui Joint Innovation Center for Life and Health & Lishui Lvgu Institute for Life and Health, Lishui, Zhejiang 323010, China | | | HE Lei | College of Life Sciences, Zhejiang University, Hangzhou 310058, China | | | TANG Jianjun | College of Life Sciences, Zhejiang University, Hangzhou 310058, China | | | CHEN Xin | College of Life Sciences, Zhejiang University, Hangzhou 310058, China | chen-tang@zju.edu.cn |
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| Abstract: |
| Compare to rice monoculture, rice-fish system often maintains a longer and deeper field water. Whether rice-fish system would increase methane（CH4）emissions from rice paddies has been a concern. In this study, we first compare yields of rice and fish, and CH4 emissions under rice monoculture（RM）, rice-fish coculture（RF）and fish monoculture（FM）in a field experiment. Then, we examine the effects of levels of fish yield and fish feed input on yields of rice and fish, and CH4 emissions by conducting controlled field experiments. We also investigate whether fish bioturbation affect CH4 emissions by a simulated mesocosm experiment. Our results showed that traditional rice-fish system（i. e. low fish yield without commercial fish feed input）had similar trend of CH4 emission flux as rice monoculture, which the emission flux gradually increased after transplantation, reaching its peak during the tillering and panicle primordium differentiating stages, and gradually decreased after the flowering stage. In the rice-fish system, fish yield increased and rice yield was stable when fish stocking density increasing with fish feed input. Compare to rice monoculture, CH4 emission flux significantly increased when fish target yield reached 1.5 t·hm-2（i.e. fish stocking density at rate of 6 000 ind·hm-2）. In the scenario where the target yield was 1.5 t·hm-2 and the total nitrogen（N）input （fertilizer-N+feed-N）is 120 kg·hm-2, as the proportion of feed-N to total N increases, fish yield significantly increases while rice yield remains stable. However, the CH4 emission flux from paddy fields showed an increasing trend. When the proportion of feed-N to total N increased to 62.5%, the increase in CH4 emission flux from paddy fields reached a significant level at P<0.05（compared to rice monoculture）. Simulation experiments showed that simulated fish activity did not significantly affect soil CH4 emission flux in paddy fields, but significantly increased the abundance of methane oxidizing bacteria functional genes （pmoA）. Our results are of significance for how to balance the rice yield, fish yield, and environmental effects of the rice-fish system to ensure its sustainable development. |
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