双季稻种植在我国粮食生产中具有重要地位，稻田土壤微生物多样性对于土壤生产潜力、土壤生态功能稳定和生态环境安全等具有重要意义。本项目拟以持续了30年的红壤性水稻土双季稻连作定位试验为基础，研究长期施肥对土壤氮库、微生物生物量氮、土壤酶活性和功能微生物多样性的影响，探明作物关键生育期土壤功能微生物群落演替以及氮转化相关功能微生物与土壤氮素的关系，阐明长期有机无机配施下土壤功能微生物多样性特征及对土壤氮素转化的影响。研究成果可揭示长期不同施肥措施对土壤功能微生物多样性的影响以及双季稻田土壤氮生物转化特征，对于指导双季稻田合理施肥和农田可持续利用具有重要意义。

Rice is China's most important food crop, and double rice cropping system plays an important role in grain production. Soil microbial diversity influenced ecosystem stability, soil production potential, soil ecosystem functioning and resilience towards stress and disturbance. This study was carried out on a long-term experiment at Nanchang County of Jiangxi Province, subtropical China, established in 1984 on reddish paddy soil under double rice cropping system with different fertilization regimes. Five treatments were selected for this study: no fertilizer(CK), balanced chemical fertilizers (NPK), chemical fertilizers substituted by organic manure from 30% to 70% (70%F+30%M, 50%F+50%M, 30%F+70%M). The aim of this study was to evaluate the effect of long term fertilizer application on the soil nitrogen transformation and soil microbial genetic diversity. Therefore, the field and laboratory incubation experiments were carried out, and soil microbial biomass nitrogen(SMBN), soil enzymatic activities were detected. Effects of long-term fertilization on abundance and community composition of ammonia oxidizing bacteria(AOB), ammonia oxidizing archaea(AOA) and denitrifier communities were studied with targeting amoA, nosZ, narG, nirK and nirS genes using quantitative real-time polymerase chain reaction (qPCR) and denaturing gradient gel electrophoresis (DGGE) , respectively. The overall objectives of this study are as: ⅰ) to examine the effect of long-term application of organic manure and mineral fertilizers on the soil enzymatic activities, soil microbial biomass nitrogen and functional gene diversity, ⅱ) to investigate the microbial community succession and dynamic of soil microorganisms at different crop growth stages, ⅲ) to show the influence of nitrifying and denitrifying bacterial communities on nitrogen transformation, and their relationship with soil nitrogen. In addition, with this study, we can enhance the research contents on the key processes and microbial mechanisms of soil nitrogen transformation, and to provide theoretical basis and scientific guidance for scientific fertilization of double rice cropping system and sustainable use of farmland.