小麦-玉米农田周年氨交换通量特征及作物氨减排潜力研究

Ammonia (NH3) exchange between the crop canopy and atmosphere is an important part of nitrogen cycling in agriculture ecosystems. It is of great scientific significance and practical value to strengthen research on the NH3 exchange mechanism and reduction technologies, which will improve fertilizer use efficiency as well as reduce atmospheric haze pollution. The study aims to quantify the NH3 exchange flux intensity between in situ wheat-maize double cropping systems and atmosphere in the North China Plain and explore the NH3 emission reduction mechanism and technical measures using the advanced technologies such as micrometeorology, inverse diffusion algorithm, double canopy resistance model simulation and online laser ammonia analyzer. The main research contents are focused on investigating the NH3 exchange fluxes and annual variation characteristics between the crop canopy and atmosphere, the distributions and influencing factors of NH3 source/sink in the crop canopy and the canopy contribution to the net NH3 exchange. The key points are to study the factors affecting canopy on NH3 emissions and re-absorption and to explore a nitrogen management scheme to reduce NH3 emission through the crop canopy absorption.

大气氨交换过程是生态系统氮素循环的重要过程。加强农田界面氨交换通量特征和减少NH3排放的作用机制研究，对提高肥料利用效率，和改善生存环境条件具有重大的科学意义与现实应用价值。本项目将以华北平原小麦／玉米两熟农田为主要研究对象，以原位定量作物与大气NH3交换通量，探索作物NH3减排机制和技术方向为目标，采用微气象法、逆扩散法和双层冠层阻力模型模拟法，以及在线激光NH3气分析仪等先进技术手段，重点研究小麦/玉米农田与大气NH3交换通量周年变化规律，作物冠层源/汇分布及影响因素，阐明作物系统与大气NH3交换通量的周年变化特征，以及作物与土壤对NH3净交换量的贡献度；并研究冠层对氮肥NH3排放的再吸收影响因素，探索冠层最大氨吸收的氮肥优化管理方案。

农田是大气 NH 3 排放的主要来源之一。农田作物冠层与大气 NH 3 存在双向交换过程，但其田间通量特征与变化影响机制仍然很不明确。本课题以华北平原小麦／玉米两熟农田为主要研究对象，采用微气象法、逆扩散法和双层冠层阻力模型等技术手段，重点研究小麦/玉米农田与大气NH3交换通量周年变化规律，作物冠层NH3源/汇分布及影响因素，阐明作物与土壤对NH3净交换量的贡献度；探索冠层最大氨吸收的氮肥优化管理方案。研究结果表明：农田大气氨浓度有着明显的季节变化，浓度一般保持在100-200ppbv之间，在7月上旬和8月中旬出现2次浓度高峰，最高浓度可达580ppbv。小麦玉米农田周年冠层氨交换通量为74.5kg ha-1，与氨浓度季节变化相似，在7月和8月出现排放高峰，最高为13.8kg N ha-1d-1。小麦返青期施肥后冠层再吸收率分为8.71 %；拔节-孕穗期为7.84 %；玉米大喇叭口-抽雄期则仅为0.67%。作物补偿点有明显季节特征，小麦开花期和玉米苗期为氨补偿点较高时段，总体小麦显著高于玉米。作物吸收能力主要取决于冠层郁闭度和空气湿度，与作物补偿点关系不明显。本研究揭示了作物冠层对大气氨交换的源汇贡献。