基于多指标的典型水旱轮作生态环境效应和经济效益的可持续性计量与评价

Agricultural activities are conducted to provide food for human being while they have a certain impact on the ecological environment, which brings about an important scientific issue of how to comprehensively quantify the environmental risks and the overall effects of ecological benefits in terms of evaluating the sustainability of a certain agricultural activity. For different paddy-upland rotations that are the important production mode of agriculture in the middle and lower reaches of the Yangtze river, there is still a lack of comprehensive and unified evaluation and quantification of the benefit characteristics, which has influenced the selective development of utilization models of paddy-upland cultivation. In this regard, this project is to establish a system of environmental impact and eco-efficiency evaluation indicators which is applicable to the paddy-upland rotation on the basis of typical paddy-upland systems, by using integrated databases such as field monitoring, model simulation, and field management, etc., and combining life cycle assessment methods with eco-efficiency evaluation methods. In addition, the environmental effects of nitrogen loss, greenhouse effect and the ecological efficiency characteristics of biomass, soil health and environmental improvement are also quantified and compared between different models of paddy-upland rotation. Through the integrated analysis to evaluate the sustainability of environmental impacts and benefits coordinated across crop rotation systems and the synergistic or offsetting effects among their indicators, the project is also to exploit the key drivers so as to find the most cost-effective and least risky production pathways, providing methodological support and practical basis for the development of environmentally-economically friendly sustainable agriculture.

农业活动在满足人类粮食需求的同时也在对农业生态环境带来一定的影响，而如何综合量化环境风险与生态效益的整体效应是评价某种农业活动是否具有可持续性的重要科学问题。水旱轮作是长江中下游农业的重要生产模式，而目前仍缺乏不同水旱轮作制度的全面、统一的效益特征评价与量化，这对水旱种植利用模式的择优发展具有重要影响。因此，本项目拟基于典型水旱制度，结合实地监测、模型模拟、田间管理等集成数据库，将生命周期评价法与生态效益评价方法结合，建立适用于水旱轮作的环境影响和生态效益评价指标体系，并量化和对比不同水旱轮作模式对氮素损失、温室效应的环境影响以及在生物量、土壤健康、环境改善等方面的生态效益特征；采用集成分析手段，评价各轮作系统环境影响与效益相协调的可持续性及其指标间的协同或抵消效应，并挖掘其关键驱动因子，以寻求效益最高-风险最小的生产途径，为发展环境-经济友好型的可持续性农业提供方法学支撑与实践依据。

基于野外监测、排放因子、经验模型等方法，通过全生命周期评价，研究休闲-水稻、紫云英-水稻、小麦-水稻、油菜-水稻、青饲小麦-水稻、蚕豆-水稻6种水旱轮作模式的环境影响与经济效益的综合评价，探索发展环境友好与经济效益最大化的可持续种植模式。.1）监测了不同水旱轮作模式的温室气体排放，得出不同水旱轮作模式CH4累积排放量为95.6~173.3 kg hm-2，其排放量与冬茬秸秆还田量和水稻产量有关；N2O累积排放量为1.5~2.5 kg hm-2，受施氮量、冬茬秸秆还田量、水稻产量和土壤有机质含量影响。.2）对不同水旱轮作模式的碳、氮、水足迹进行了分析，得出小麦-水稻轮作的单位面积碳足迹最高，油菜-水稻轮作的单位面积氮足迹和水足迹为最高；碳足迹中水稻淹水引起的CH4排放和化肥生产引起的温室气体排放贡献最大，氮足迹中NH3挥发所占比例最高（50.5%～61.7%），水足迹中绿水占最大的来源（48.9%～52.5%）。.3）评估不同水旱轮作模式的周年土壤碳汇潜力，得出油菜-水稻轮作的周年土壤固碳潜力最高，为5.4 t CO2-eq ha-1。作为温室气体减排的有效途径，紫云英-水稻轮作的土壤碳汇可以抵消约最高70%的温室气体排放，而青饲小麦-水稻轮作的碳汇只能抵消约23.5%的温室气体排放。.4）评价了不同水旱轮作模式的周年土地生产力和经济效益，得出青饲小麦-水稻轮作的周年经济效益最高，是最低效益油菜-水稻轮作的1.63倍。另外，与传统小麦-水稻轮作方式相比，紫云英-水稻轮作的周年效益将降低15%，但另一方面每年却减少了2.3 t·CO2-eq hm-2的排放效应。.5）综合评价了六种水旱轮作系统的环境影响效应，各轮作模式的环境影响排序为休闲-水稻<紫云英-水稻<蚕豆-水稻<油菜-水稻<青饲小麦-水稻<小麦-水稻；其中氨挥发是最大贡献者（60.7%-66.7%），其次是蓝绿水（17.5%-26.6%）和温室气体排放（6.8%-13.3%）。.6）对不同水旱轮作模式经济效益和环境影响集成足迹进行对比，得出小麦-水稻轮作的环境影响集成足迹最高，是紫云英-水稻轮作模式的1.3倍；但另一方面小麦-水稻轮作模式的周年经济效益只是紫云英-水稻轮作模式的1.2倍。