豫中农田土壤改良对生态系统碳收支及净温室效应影响研究

Application of crop straws and their biochar and incorporation of green manure are effective measures for soil amelioration. The inputs of organic materials could promote carbon sequestration. However, the added organic materials could also alter soil C and N cycles, which has an impact on greenhouse gas emissions and net global warming potential. In order to elucidate the characteristics of annual greenhouse gas emissions and their key drivers, we will continuously monitor the emissions of N2O, CH4 and CO2 in situ, as well as the soil variables (soil temperature, moisture, mineral N, and soluble organic carbon, etc.) in a field experiment in central Henan area. The net ecosystem carbon budget and soil C sequestration will be evaluated by determining the net primary production, soil heterotrophic respiration, C inputs from the organic materials and the biomass removed from the system. The greenhouse emissions derived from the fertilizers, organic materials, plastic film, pesticides, and the diesel fuel during irrigation and farming operations annually will be calculated. On the basis of these, we will also assess the net global warming potential and the GHG intensity of the different methods for soil amelioration. This research is helpful in comprehensively evaluating the environmental effects and providing a theoretical support for green development.

添加作物秸秆和生物质炭、种植并翻压绿肥是改良土壤的有效措施。向农田添加有机物料一方面会增加土壤碳库，另一方面会改变土壤碳、氮循环，影响温室气体排放和净温室效应。本研究以无机肥处理为对照，拟通过连续三年田间定位试验测定CO2、N2O和CH4排放速率和土壤环境因子（土壤温度、水分、矿质氮、水溶性有机碳等），阐明不同土壤改良措施下豫中农田土壤温室气体周年排放特征，并揭示关键影响因子；通过测定农田生态系统净初级生产力，土壤异氧呼吸，有机物料投入、作物收获等，估算不同土壤改良措施下生态系统净碳收支，并估算土壤固碳效应；利用生命周期评价法计算由化肥投入、有机物料投入、地膜投入、灌溉耗能、机械燃油、农药施用等产生的等当量CO2，估算农田净温室效应及温室气体排放强度，综合评价不同土壤改良措施下的环境效应，为农业绿色发展提供理论支撑。

添加有机物料在增加土壤固碳的同时也可能会增加温室气体排放。本研究探索了不同土壤改良措施下豫中烟田生态系统CO2、N2O和CH4排放特征及其主要影响因素，净碳收支和固碳效应，并利用生命周期评价法对净温室效应进行系统评价。取得的主要结果和结论有：.（1）土壤异养呼吸（Rh）和CH4吸收速率整体表现为烟苗移栽后逐渐升高，在7-8月份达到峰值，之后逐渐降低。Rh与土壤温度、易氧化有机碳含量显著正相关。生育期CH4吸收与WFPS、土壤硝态氮含量呈负相关，与土壤温度、pmoA基因呈正相关；休闲期影响CH4吸收的主要因素是土壤温度。生育期降雨或灌溉后出现N2O排放峰，休闲期N2O排放维持在较低水平。N2O排放与土壤WFPS、硝态氮含量、nirS和nirK基因数量正相关，与amoA-AOA基因数量负相关。在仅施用氮磷钾处理（NPK）的基础上，种植并翻压黑麦草（NPKG）、添加小麦秸秆（NPKS）和生物炭（NPKB）处理均显著增加了Rh累积排放；NPKS和NPKG处理增加了生育期及全年N2O排放，NPKB处理降低了N2O排放；添加有机物料减少了CH4吸收。.（2）不施肥（NF）和NPK处理生态系统净碳收支为负值，添加有机物料处理净碳收支为正值；各处理生态系统年净碳收支为-1.28~1.70 t C hm-2，添加有机物料增加了Rh，但其投入的碳量大于其引起的碳排放，因此有利于烟田生态系统由“碳源”转换为“碳汇”，且以生物炭处理固碳效应最大。.（3）不同处理全年净温室效应为377.54~1587.81 kg·CO2-eq·hm-2，添加有机物料处理主要通过增加固碳效应降低了净温室效应，其中NPKB处理净温室效应和温室气体排放强度最低。.综上所述，添加有机物料能够提高烟叶产量，增加土壤固碳并降低综合净温室效应和温室气体排放强度，其中施用烟秆生物炭处理对豫中烟田生态系统固碳减排的效果最佳。