斜发沸石对干湿交替灌溉驱动下稻田甲烷和氧化亚氮排放的影响机理研究

Rice fields have been identified as an important source of atmospheric methane (CH4) and nitrous oxide (N2O). Meanwhile, alternate wetting and drying irrigation (AWD) is the most widely used among various water-saving techniques in rice fields. Enhanced soil oxidation - reduction potential caused by AWD inhibits CH4 emission, but rapid fluctuations in soil moisture, soil redox potential and water-filled pore space under AWD intensify N2O emissions. Addition of zeolite to soil increases soil water holding capacity and nutrient preserving capability, resulting in decline in N2O emission. However, limited information on CH4 and N2O emissions is available for zeolite-amended paddy field under AWD. In this project, a dynamic centrifuge experiment will be conducted to determine effects of application rate and particle size of zeolite on water holding capacity and water retention potential of paddy soils. A laboratory soil column experiment will be used to determine that correlation curve of relationship between application rate and particle size of zeolite, and soil moisture and nitrogen availability under continuous flooding and AWD irrigations. Two lysimeter experiments will be conducted under automatic canopy to reveal influence mechanism that application AWD reduces CH4 emission, and incentive mechanism of zeolite amendment to reduce N2O emission under the rapid fluctuations in soil moisture, soil redox potential and water-filled pore space of AWD. It concludes that it is of importance to conduct this study to clarify the potential of zeolite addition to AWD paddy field to reduce water and fertilizer use and maintain or improve grain yield while lowering CH4 and N2O emissions, providing a theoretical basis and technical support for ecological civilization construction of rice production system.

稻田是CH4和N2O温室气体的重要排放源。为充分发挥干湿交替灌溉技术的节水效果和对稻田CH4气体排放的抑制作用，解决因其频繁干湿交替环境而导致N2O过多的排放，探索斜发沸石对干湿交替灌溉下稻田中CH4和N2O的排放影响机理，本项目拟通过室内离心机试验、土柱试验和蒸渗仪试验，明确沸石用量和粒径对稻田土壤持水性能和保水潜力的影响，构建常规淹灌和干湿交替灌溉下土壤含水率和有效氮与沸石用量和粒径之间的关系曲线，阐明稻田应用干湿交替灌溉降低CH4排放的作用机理，探索斜发沸石在土壤水分饱和与非饱和、氧化与还原等干湿交替环境下降低稻田N2O排放的激励机制，阐明其在节水省肥和增产的同时对降低温室气体排放的动力机制，以期实现在减少东北地区稻田水氮资源消耗的基础上，降低水稻生产环境代价，为生态文明建设提供理论依据和技术支撑。

干湿交替稻田生态系统具有显著的增/稳产节水和降低甲烷排放等诸多优势，但也因频繁干湿交替环境而导致其N2O快速排放。本项目针对该核心问题，以干湿交稻田生态系统为研究对象，以不同用量及粒径的斜发沸石为试材，利用土壤水分特征曲线试验揭示了斜发沸石土壤持水特性和改善土壤水分状况的作用机理，利用斜发沸石等温吸附、吸附动力和热力学实验，阐明了斜发沸石对氮素的吸附-解吸动力机制和合作竞争机制；通过原位大田研究了干湿交替灌溉下斜发沸石对 CH4和 N2O 排放影响研究。结果表明：不同粒径和用量斜发沸石在不同土壤基质势下（0~2000 kPa-1）均能显著提高土壤含水率，如饱和含水率增加5.1%~32.8%、田持含水率增加3.3%~12.0%，基质势超过1000 kPa-1后，斜发沸石对土壤持水增效减弱。斜发沸石提高作物有效水容量3.2~18.8%，易效水容量1.2~12.2%，且细粒径优于粗粒径。斜发沸石对NH4+的吸附呈现“快速吸附，缓慢平衡”的特点，等温吸附过程符合Langmuir方程，饱和吸附量可达44.7 kg N-NH4+ t-1。解吸过程符合Hill方程，5 min即可达到全部解吸量的70%，最终解吸量为39.79 mg NH4+ g-1。钾离子的存在会抑制沸石的铵吸附量，且随着钾离子浓度的增加，抑制作用增加，当溶液中钾的含量较低时，铵的存在会促进沸石自身钾的释放。土壤Eh在AWD（261.38-451.74 mV）下高于CF（215.67-429.08 mV）。Z10处理土壤Eh分别比Z0和Z5低4.14-7.62%和2.07-3.96%。添加5t和10t Z ha-1可使两种灌溉方式下的NH4+（5.24-32.71%）和NO3−（7.58-23.18%）浓度增加。三年来，AWD灌溉显著降低CH4累积排放量，分别比CF灌溉平均减少71.38%、54.29%、71.07%。 Z5和Z10沸石水平降低了N2O的平均累积排放量，分别为9.27%和13.05%。总之，AWD 模式结合 5~10 t·ha-1 斜发沸石施用，显著减少了稻田CH4、N2O排放和产量尺度GWP，同时也实现了水稻节水增产的目标，且这些正效应至少可以维持3年，这对降低水稻生产的资源和环境代价，并保障稻田生产系统的可持续发展具有重要意义。