水稻土硝化能力对低氧环境的适应机理及其与氮损失的关系

Nitrification is not only an important process of nitrogen (N) cycling, which determines the dominant forms of inorganic N, but also an important process closely related to denitrification loss and N use efficiency in paddy soils. The investigation on mechanism of low oxygen adaptation of nitrification ability and its relationship with N loss in paddy soils is important significances to understand the N cycle in paddy soils, to optimize N fertilization, and to reduce the loss of N in paddy fields. In this study, paired 15N tracing incubation experiment combined with mathematical modelling method were conducted to investigate the minimum oxygen concentration, at which nitrification activities are substantially suppressed; molecular biological techniques were used to study the mechanism of nitrification microorganism adaptation to low oxygen concentration on the basis of different paddy soils. The denitrification loss was determined by using 15N tracing and soils core method under flooding condition in the laboratory to analyse the effects of soil nitrification abilities adaptation to low oxygen concentration on N losses vis denitrification in paddy soils. The results would be helpful to deep understand nitrification and its effect factor in paddy fields, to better understand the mechanisms of N loss via denitrification, and provide the scientific basis knowledge to management nitrogen fertilizer reasonable for better understand nitrification and denitrification in paddy fields.

硝化作用既是决定水稻土无机氮形态的重要氮转化过程，也是与稻田氮损失和水稻氮肥利用率密切相关的氮转化过程。深入研究稻田长期淹水的低氧条件下，硝化能力对低氧环境的适应机理及其与氮损失的关系，对于认识稻田氮循环过程，合理施用氮肥，减少氮损失具有重要意义。本项目以硝化能力差异较大的水稻土为主要研究对象，采用15N同位素成对标记技术与数学模型相结合的方法研究水稻土硝化能力受到抑制的最低氧气浓度；采用分子生物学方法研究稻田硝化微生物对较低氧气浓度产生适应的相关机理；采用室内土柱试验与15N同位素示踪技术相结合的方法研究淹水低氧条件下水稻土反硝化氮损失，分析水稻土硝化能力对低氧环境的适应与反硝化氮损失的关系。研究结果将有助于深入认识稻田硝化作用及其关键影响因素，阐明稻田反硝化氮损失的相关机理，为根据稻田土壤硝化和反硝化特性进行氮肥管理提供科学依据。

硝化作用既决定水稻土无机氮形态的重要氮转化过程，也是与稻田氮损失和水稻氮肥利用率密切相关的氮转化过程。但稻田长期淹水的低氧条件下，硝化能力对低氧环境产生适应的相关微生物机制及其与氮损失关系的研究还不够深入。本项目以硝化能力差异较大的水稻土为主要研究对象，采用15N同位素示踪技术与数学模型相结合的方法明确了水稻土硝化能力受到抑制的最低氧气浓度；采用高通量测序、实时荧光定量PCR等分子生物学技术，系统研究了不同氧气浓度下硝化微生物功能基因丰度、群落结构组成及其影响因素，明确低氧条件下水稻土硝化能力可以进行的主要微生物作用机理；通过土柱培养实验研究不同硝化能力土壤的反硝化氮损失并分析二者的关系。通过水稻盆栽实验进一步验证水稻土硝化能力与水稻产量及植株氮肥利用率的关系，旨在为稻田氮肥管理提供科学依据。