连续多年施用生物炭对华北农田土壤N2O排放的影响及机制研究

Nitrous oxide is one of the most greenhouse gases. Agriculture soils are the main emission sources. In recent years, biochar has been increasingly seen as effective measures to increase soil nutrient availability and mitigate greenhouse effect, yet its effect on the mechanism of nitrous oxide production and emission is not clear. Our previous researches found, biochar changed soil physical and chemical properties after several years of successive application, which will affect the production and emission of nitrous oxide. This study is attempted to research the effects of biochar on nitrous oxide emissions and its microbial response mechanism in the high-yield farmland of the North China Plain. We will carry out field experiment and outdoor pot experiment simultaneously. The static chamber-gas chromatograph method and microbial molecular technology (real-time PCR) will be used to study the biochar effects on nitrous oxide emissions and the abundance and community composition of ammonia oxidizing bacteria and denitrifying bacteria, The effects of hydrothermal factors, biological factors and soil factors on N2O flux will be considered comprehensively. We try to reveal the mechanism of biochar on soil nitrous oxide emission in North China Plain. This research would be of great scientific and practical significance in the respects of understanding the reduction mechanism of biochar, improving nitrogen fertilizer use efficiency and improving soil nitrogen cycling.

N2O是重要的温室气体之一，农业土壤是其最主要的排放源。近年来，生物炭已日益被视为增加土壤养分有效性、缓解温室效应的有效措施，然而其对土壤N2O排放的影响机理尚不明确。本课题组前期研究发现，连续多年施用生物炭显著改变了土壤的理化特性，这将对N2O排放产生重要影响。本研究拟以华北高产农田冬小麦-夏玉米轮作体系为研究对象，采用田间定位试验和室外培养试验相结合的研究方法，应用静态暗箱-气相色谱法和实时荧光定量PCR技术，研究生物炭输入对温室气体N2O的减排效应以及对氨氧化细菌和反硝化细菌丰度和多样性的影响，并综合考虑水热因素、微生物因素、土壤因素等环境因素对N2O通量的影响。试图揭示长期施用生物炭对华北农田土壤N2O排放的影响机理。这对深入理解生物炭对N2O的减排机理、提高氮素的利用率、改善土壤氮素循环具有重要的科学意义和现实意义。

项目背景：.农业土壤是N2O最主要的排放源。施用生物炭被视为能够增加土壤养分、缓解温室效应的有效措施，然而其对土壤N2O排放的影响机理尚不明确。本研究以华北高产农田冬小麦-夏玉米轮作体系为研究对象，应用静态暗箱-气相色谱法和实时荧光定量PCR技术，研究生物炭输入对N2O的减排效应以及对氨氧化细菌和反硝化细菌丰度和群落结构的影响，并综合考虑水热因素、微生物因素、土壤因素等环境因素对N2O通量的影响。.主要研究内容：.（1）施用生物炭对华北农田土壤N2O通量与排放规律的影响；.（2）施用生物炭对土壤微生物量氮、矿质氮、pH含量的影响；.（3）施用生物炭对土壤氨氧化细菌和反硝化细菌丰度和群落结构的影响。.重要结果：.（1）在小麦-玉米轮作周期内，各处理N2O通量的动态变化趋势基本一致；施用低量生物炭可显著提高N2O排放量，施用高量生物炭有利于减少N2O排放量。 .（2）施用生物炭与秸秆还田显著提高了土壤AOA、AOB基因的丰度，且同一作物下土壤AOA的拷贝数高于AOB。施用生物炭和秸秆还田显著提高了nirK、nirS和nosZ基因的丰度以及nirK/nirS与( nirK + nirS) /nosZ的比例，且小麦季土壤中nirK和nosZ基因的拷贝数低于玉米季。.（3）在玉米生育期，秸秆还田处理N2O排放量显著增加，小麦生育期N2O排放量显著减少。无论是玉米季还是小麦季，N2O排放量与土壤中的硝态氮和铵态氮含量、土壤含水量均呈现极显著正相关关系，而与土壤pH呈现显著负相关关系。小麦季，N2O排放量与AOB拷贝数呈现显著负相关关系；玉米季，N2O排放量与nosZ基因呈现显著负相关关系。.关键数据：.连续2年的N2O通量数据；.连续2年的土壤温度和土壤水分的观测数据；.连续2年的土壤硝态氮和铵态氮含量数据；.连续2年的土壤微生物量碳、氮数据；.连续2年的土壤pH的变化数据；.小麦玉米关键生育期（每种作物5次）功能基因的丰度、群落结构的测定数据。..以上结果对深入理解生物炭对N2O的减排机理、提高氮素的利用率、以及秸秆的资源化利用具有重要的科学意义和现实意义。