基于氮素回用-生物炭负载氮对植烟土壤NH3挥发和N2O排放的影响及机制

Reusing the nitrogen from non-point polluted water to the field has great practical significance. The biochar has been demonstrated to be a safe and effective carrier for returning nitrogen from non-point polluted water to the field. However, few studies were concentrated on the influence of biochar loading nitrogen on the ammonia (NH3) volatilization and nitrous oxide (N2O) emission and their related mechanisms. In this project, therefore, soil column experiments are constructed to study the dynamics and accumulation of NH3 volatilization and N2O emission under the application of biochar loading nitrogen with various ratios of adsorbed-nitrogen in biochar to fertilizer-nitrogen. Besides, the correlations between NH3 volatilization/N2O emission and soil physicochemical properties, microbial biomass, urease activity, key functional genes of nitrogen transformation and tobacco growth will also be investigated. This study will be beneficial to provide the theoretical basis and dates support to generalize the application of returning biochar loading nitrogen to the field. Meanwhile, it is also of great theoretical and practical significance to promote the health and sustainable development of agriculture and the zero growth of chemical fertilizer of China.

面源污染水体氮素农田回用具有重大现实意义。生物炭已被证明可以作为载体实现面源污染水体氮素由水体到农田的安全有效迁移，但生物炭负载氮还田，特别是负载氮和肥料氮不同配施比例，对土壤气态氮素（NH3和N2O）损失的影响规律及其内在机制却鲜有报道。基于此，本项目通过土柱试验，设定不同生物炭负载氮和肥料氮配施比例，探讨生物炭负载氮施加条件下，土壤NH3挥发和N2O排放的规律及其与土壤理化性质、微生物生物量、脲酶活性、氮转化关键功能基因和烤烟生长之间的相互关系，研究结果有助于为基于氮素回用的生物炭负载氮还田提供理论基础和数据支撑。同时，对于推动农业健康可持续发展和国家化肥零增长具有重要的理论意义和现实意义。

面源污染水体氮素回用具有重大现实意义。利用生物炭吸附面源污染水体中的NH4+-N并将其进行还田可实现此氮资源由水体到农田的安全有效迁移，而探索生物炭负载NH4+-N对土壤气态氮素排放、土壤质量、烤烟农艺性状和烤烟氮素利用效率的影响对面源污染防控、国家化肥零增长战略实现和现代农业可持续发展具有重要的理论和现实意义。基于此，项目组通过土柱试验，设定不同生物炭负载氮和化肥氮配施比例，研究了生物炭负载氮添加对土壤NH3挥发/N2O排放规律、植烟土壤理化性质、烤烟农艺性状和烤烟氮素利用效率的影响。研究结果表明，（1）沼渣生物炭中的C-C和含氧官能团参与了NH4+-N的吸附，NH4+-N吸附后主要进入了生物炭内部，导致了生物炭比表面积、孔隙体积和平均孔径的降低；此外，生物炭负载氮显著降低了土壤NH3挥发和N2O排放，其减排效果显著优于生物炭化肥配施，其中60%的生物炭负载氮替代比例对土壤气态氮素的减排效果最好，具体机制（N2O减排）是：土壤pH降低，nosZ基因丰度增加，nosZ基因群落结构改变，N2O还原酶活性增强，导致N2O还原为N2强度增加，最终引起N2O排放量降低；（2）60%的生物炭负载氮替代比例最有利于土壤质量提高、烤烟农艺性状改善和烤烟氮素利用效率提高。综上，本研究从土壤温室气体减排、土壤质量提高和作物生长等方面联合发现了基于养分回用-氮肥替代的沼液NH4+-N吸附净化-回收还田技术的可行性和优越性，实现了面源污染水体NH4+-N由水体到农田的安全有效迁移。因此，本研究推荐60%生物炭负载氮替代比例应成为未来化学氮肥的有效替代方式。