磷对稻田甲烷产生及氧化的调控及其机制研究

Phosphorus fertilization strategy of few or no in rice season and more in wheat season can increase the use efficiency of P and reduce the P loss through runoff and leaching effectively. However, CH4 emission of no P fertilizer in rice season found increased 33-40% when compared with those with P fertilizer. Does this phenomenon exist widely? So far, no systematic research were carried out to investigate the effect of phosphorus on methane emission in paddy field, the mechanism of P to regulate the production and oxidation of methane in paddy field is still unclear. Therefore, in this project, soil microcosm simulation experiments with different P levels, pot experiments with 2 different rice cultivars and long-term field experiments with & without P application for different years will be conducted. The influences of P on rice growth, root exudates and oxygen secretion capacity, the availability of C, N, P in soil and the microenvironment of rhizosphere will be investigated. Then, using the molecular biology methods, such as high-throughput sequencing and C13- marker DNA-SIP, to analyze the response of methanogens and methanotrophic community, populations and traits to P, and reveal the regulation mechanism of phosphorus on methane emission in paddy field. The research results will provide a scientific basis and reference for the greenhouse gas effect evaluation of phosphorus fertilizer application in rice, as well as the suitable phosphate fertilizer input for grain production, non-point source pollution control and greenhouse gas emission reduction.

稻田磷肥的“旱重水轻”施肥策略是有效提高磷素利用率、减少磷素流失的一个有效技术途径。然而田间观测发现稻季长期不施磷处理促进了甲烷的排放。这一现象是否具有普遍意义，磷对稻田甲烷排放的影响有多大，是如何调控稻田甲烷的产生及氧化，目前还缺乏系统研究和明确答案。为此，本项目通过不同磷添加水平的土壤微宇宙模拟试验、不同甲烷排放能力水稻品种的磷添加盆栽试验以及不同年限长期不施磷与施磷的大田定位试验，明确磷对水稻植株生长、根系分泌物及泌氧能力、土壤碳氮磷有效性、根区微环境等的影响，并利用先进的分子生物学手段如高通量测序、13C标记DNA-SIP技术分析产甲烷菌以及甲烷氧化菌群落结构组成以及活性对磷的响应策略，揭示磷对稻田甲烷排放的调控作用及其机制。研究结果将为磷肥“旱重水轻”施肥策略的温室气体效应评价，以及粮食生产、面源污染控制以及温室气体减排三者协调的适宜磷肥投入提供科学依据。

稻田磷肥的“旱重水轻”施肥策略是有效提高磷素利用率、减少磷素流失的一个有效技术途径。然而田间观测发现稻季长期不施磷处理促进了甲烷的排放，这一现象是否具有普遍意义，磷对稻田甲烷排放的影响有多大，是如何调控稻田甲烷的产生及氧化，目前还缺乏系统研究和明确答案。为此，以两个长期不施用磷肥的水稻定位试验田为依托，开展了3年多的野外田间观测以及添加磷的田间微区试验和盆栽试验，结合文献meta分析，初步探讨了磷对稻田甲烷排放的影响及其调控机制。研究结果发现长期不施磷处理显著促进了稻田CH4 排放尤其是水稻分蘖期的CH4 排放；长期不施磷处理土壤有效磷含量尤其是Fe-P、Ca-P和活性有机磷含量显著下降，水稻为满足自身生长需求而使根系分泌了更多的有机酸，刺激土壤磷酸酶活性以及解磷等相关微生物显著增加，促进稻田土壤磷活化，同时提升了土壤DOC含量，增加了产甲烷菌的反应底物，提升了产甲烷菌的丰度和多样性并抑制了甲烷氧化菌的丰度和多样性，最终导致CH4排放的增加。不同土壤碳水平下缺磷土壤的磷添加试验也反向证明了这一机制，表明土壤磷的有效性是影响稻田甲烷排放的一个重要因素。综合考虑作物高产、磷肥的高效利用以及甲烷排放等环境效应，稻田应合理施用磷肥，避免磷肥用量过高引起的磷流失风险增加以及磷肥用量过低引起的甲烷排放增加和产量降低等问题。