长期不同施肥模式下稻田厌氧氨氧化活性差异的土壤-微生物机理

Anaerobic ammonium oxidation (anammox) is an important pathway for nitrogen loss in paddy field ecosystem. China is a major producer of rice and nitrogen fertilizer. In paddy field ecosystems, various amounts and forms of nitrogen fertilizer have been invested in a long time, resulting in changes of soil structure and nutrient, which have an effect on microbial composition, quantity and activity. Nevertheless, the understanding of the soil-microbiological mechanisms of differences in anaerobic ammonium oxidation under different fertilization systems is very limited. In this study, four types of fertilizers i.e., no fertilizer, mineral fertilizer, mineral fertilizer with cattle manure and mineral fertilizer with straw residues were selected to apply in a rice paddy ecosystem. In site sampling and microcosm incubation with isotope-tracing technique, quantitative PCR assay and gene clone libraries were used to investigate (1) the difference of soil anaerobic ammonium oxidation activity between different fertilization paddy fields, (2) the difference of the functional microorganisms abundance and community structure, and (3) the internal relations between anammox, soil structure and nutrient balance under four different kinds of long-term fertilizer treatments. The research may reveal the response mechanisms of microbial community structure, quantity and activity of anaerobic ammonium oxidation in paddy field, and provide scientific basis for rational fertilization and understanding of anaerobic ammonium oxidation process in a wetland ecosystem.

厌氧氨氧化是稻田生态系统氮损失的重要途径。中国是水稻生产和氮肥消费大国，在稻田生态系统中，各种不同形式的氮肥长期大量投入，导致土壤结构、营养物质发生改变，进而对微生物组成、数量和活性产生影响，尽管如此，当前对不同施肥制度下厌氧氨氧化差异的土壤-微生物机理的认识非常有限。本项目拟选择不施肥、单施无机肥、无机肥加秸秆还田和无机肥与牛粪配施四种不同长期施肥模式水稻田，采用野外原位采样结合室内微宇宙培养，应用稳定同位素示踪、实时荧光定量和克隆文库技术开展以下几个方面的研究：（1）长期不同施肥稻田土壤厌氧氨氧化活性差异；（2）不同施肥稻田土壤厌氧氨氧化菌数量与群落结构差异；（3）长期不同施肥稻田土壤结构和营养物质的差异与厌氧氨氧化菌组成、数量和活性的内在联系。揭示稻田厌氧氨氧化微生物群落结构、数量和活性对长期不同施肥的响应机理，为合理施肥和理解湿地生态系统厌氧氨氧化过程提供科学依据。

施肥影响农业土壤厌氧氨氧化过程氮素损失，但机理尚不清楚。依托本项目，利用同位素示踪和微生物分子生态技术明确了南方红壤性水稻土不同施肥后厌氧氨氧化过程氮素损失差异的机理，长期氮磷钾施肥提高厌氧氨氧化菌丰度，降低厌氧氨氧化菌多样性，并未显著增加稻田厌氧氨氧化过程氮损失，长期氮磷钾加秸秆处理提高厌氧氨氧化菌丰度、活性和多样性，增加稻田氮损失。揭示了不施肥的盐碱水稻土壤氮素损失剖面特征，上层土壤氮素损失主要由厌氧氨氧化驱动，主导菌属为Candidatus Scalindua，其次为Candidatus Kuenenia，而深层土壤氮损失主要由反硝化驱动。项目在农业土壤氮素损失机制、完善氮素收支平衡、调控氮素损失等方面取得创新性成果。研究成果发表于Environmental Pollution、Biology and Fertility of Soils、Soil and Tillage Research、土壤学报、农业现代化研究。