长期施肥下双季稻田根际微生物对土壤碳、氮转化机制研究

As soil rhizosphere carbon and nitrogen transformation playing a key roles in soil quality and plant nutrition, and the mechanism of soil carbon and nitrogen cycling in rhizosphere soils under different fertilizer regimes could be explored on the basis of long-term fertilizer experiment. In preliminary studies, the effects of long-term fertilization practices on soil microbial biomass carbon and soil microbial biomass nitrogen content, soil microbial community structure and quantity relative with soil rhizosphere nitrogen and carbon cycle in double cropping rice paddy fields system were investigated, and there were significantly difference in soil microbial biomass carbon and soil microbial biomass nitrogen content, soil microbial community structure and quantity among the different fertilization practices. But its formation mechanism is still not clear. Based on a long-term fertilizer experiment over 33 years in double cropping rice paddy soils in Ninxiang of Hunan Province, we characterize of microbial community carbon source utilization patterns (soil organic matter and rhizodeposition) in the rhizosphere soil, analyze comprehensively the microbial community structure associated with soil rhizosphere carbon cycle by using PCR-DGGE, stable carbon isotope probe technique and Illumina pyrosequencing technique, and so on. The functional gene abundances involved in nitrification and denitrification (bacterial amoA, archaeal amoA, nirK, nirS, nosZ), and the influences of carbon resources on the diversities and functions of ammonia oxidizers and denitrifier community in both the rhizosphere soil and bulk soil will be investigated. This research would theoretically contribute to explore the microbial mechanism for carbon and nitrogen turnover in the rhizosphere soil under long-term fertization practices, and the outcome through this research would be of great practical significance to balanced fertilization and soil nutrient managements in paddy field managements, so as to realize sustainable utilization of farmland.

根际碳、氮转化对于土壤质量和作物营养极为重要，利用肥料长期试验可以确切认识不同施肥下根际微生物参与土壤碳、氮循环的机制。前期研究中，我们发现长期不同施肥下双季稻田土壤微生物量碳、氮含量及与碳、氮循环相关的部分土壤微生物种类和数量均存在显著差异，但其形成机理仍不清楚。本项目拟以湖南双季稻主产区长达33年肥料长期定位试验为基础，应用PCR-DGGE、稳定性碳同位素探针技术和高通量测序相结合技术研究长期不同施肥下土壤微生物对根际固有碳和植物源碳的利用特征，与根际碳利用相关的土壤细菌高通量测序，根际土壤硝化与反硝化菌群功能基因的数量动态，以及土壤碳对根际硝化与反硝化菌群落结构和功能的影响，以阐明不同施肥下根际微生物参与土壤碳、氮循环的机制。本项目对于深入揭示长期施肥下根际碳、氮转化特征及其分子生态学机理具有重要理论价值，研究成果对于指导平衡施肥与土壤养分管理，实现农田可持续利用具有重大实践意义。

根际碳、氮转化对于土壤质量和作物营养极为重要，利用肥料长期试验可以确切认识不同施肥下根际微生物参与土壤碳、氮循环的机制。本项目以湖南双季稻主产区长达33年肥料长期定位试验为基础，应用PCR-DGGE、稳定性碳同位素探针技术和高通量测序相结合技术开展研究，探明了长期不同施肥下土壤微生物对根际固有碳和植物源碳的利用特征，明确了根际土壤硝化与反硝化菌群功能基因的数量动态，土壤碳对根际硝化与反硝化菌群落结构和功能变化规律，阐明了不同施肥下根际微生物参与土壤碳、氮循环的机制。项目研究期间，发表研究论文12篇、出版学术专著1部，培养研究生1名，全面实现了项目的设计，并完成了项目的研究目标。通过本项目研究实施，揭示了长期施肥下根际碳、氮转化特征及其分子生态学机理，研究成果对于指导平衡施肥与土壤养分管理，实现农田可持续利用具有重大实践意义。