秸秆源黑炭施用对农田化肥氮去向的影响及定量评价

Most concern has hitherto focused on application of biochar to cropland as an option of carbon sequestration and soil reclaimation with virtually little attention paid to the fate of N when associated with biochar-treated soils. It is very necessary to improve our current understanding of the intrinsically linked interatction between biochar and the N cycle in intensive agricultural systems. The objective of the project is therefore, to investigate the various fate of fertilizer N as affected by straw-derived biochar application and environmental consequences in rice/wheat and maize/wheat rotated crop lands from both the Taihu lake region and the North China Plain. We will perform experiments including soil columns, field plots and 15N microplots to simultaneously N recovery, soil residual, N losses(NH3 volatilization, leaching, runoff, denitrification) under different rotated agricultural systems mentioned above with biochar treated at different rates . The results from this project would be helpful for the next research on the chemical and biological mechanisms of N transformation and migration as affected by biochar. The information that the negative or positive effects of biochar probably existed on various fate of fertilizer N could also provide more sights for better evaluation the application prospect of biochar as an option of carbon sequestration and soil reclaimation.

国际上对生物黑炭的关注多聚焦于其固碳减排和改良土壤的功能，而较少关注其施入土壤后对氮素行为的扰动。本研究将在已有工作的基础上，拟选择华北平原和太湖平原的主要轮作农田（旱旱轮作、水旱轮作），通过种植作物的土柱、15N微区和小区试验，系统研究秸秆源黑炭施入农田后对化肥氮去向的影响，包括作物利用、土壤残留、挥发、径流、淋洗和反硝化等。为深入研究黑炭对农田土壤氮素行为(转化、迁移)的影响机制提供基础科学数据，也为从氮的角度评价黑炭作为增汇减排和改良土壤的功能及其应用前景提供必要理论支撑。

受启于亚马逊流域黑土“Terra Preta”的探究，科学家提出将生物质黑炭技术作为应对全球气候变化的潜在措施。中国秸秆年产近7亿吨，但其利用率不足50%。秸秆炭化还田被视作实现农田肥力改良、固碳减排、资源利用的多赢之举。由于黑炭独特的性质及其施入后对土壤属性的改变，秸秆炭化还田会对包括碳氮磷硫等元素循环产生干扰。在减氮增产背景下，开展黑炭对农田氮素循环影响研究具有重要意义。本项目选择我国典型农田土壤及作物体系，通过室内受控、土柱模拟、田间小区等试验方法，采用15N示踪、氦环境培养、高通量测序等手段，研究了长期秸秆炭化还田（设每季黑炭施用0、2.25、11.3、22.5 Mg ha-1等处理）对土壤氮素迁移转化过程、农田化肥氮去向的影响。主要结果表明:1）长期秸秆炭化还田一致促进红壤、潮土及水稻土等土壤上作物生长及氮素吸收，具有减少氮素流失及N2O排放的潜力，但对氨挥发影响因稻麦（水旱）季各异：稻季降低氨挥发，麦季则表现为促进作用。2）秸秆黑炭施用可提高小麦季氮肥利用率、降低总损失，对水稻季无明显影响；土壤供氮及作物地上部氮转运能力提高是秸秆黑炭提高太湖平原水稻土稻麦产量的主要原因。3）秸秆炭化还田能显著提高酸性红壤的硝化潜力，促使其氨氧化微生物优势种群向碱性潮土靠拢，改变的pH, NH4+, TN 和C/N等环境因子是主要因素；4）等碳量下，秸秆黑炭一次添加和长期连续施入两种方式对太湖平原水稻土硝化及反硝化活性具有一致促进作用，但前者影响强度高于后者；淹水条件下, 秸秆黑炭施用可降低N2O排放, 可能与N2O还原基因nosz丰富度增加有关。上述结果暗示，长期秸秆炭化还田影响农田氮循环，具有氮污染减排潜力，可为基于氮的角度科学评价秸秆炭化还田作为“多赢之举”的功能及其应用前景提供部分重要理论支撑。下一步将继续坚持已建设各定位试验平台系统长期监测，以期科学论证我国主要农区秸秆炭化还田的可行性。截止目前，已发表与上述内容相关的SCI论文7 篇，EI论文1 篇，中文核心1篇。