化肥减量与有机物料添加对华北潮土微生物氮循环功能基因丰度和氮转化遗传潜力的影响

有机物料作为生态友好型的化肥替代品为农业生态系统带来了巨大的经济和环境效益.然而，在化肥减量的基础上添加有机物料会对土壤氮（N）循环产生何种影响依旧知之甚少.在此，设置了常规施肥（NPK）、化肥减量（NPKR）、化肥减量配施秸秆（NPKRS）、化肥减量配施有机肥（NPKRO）、化肥减量配施秸秆和有机肥（NPKROS）共5种施肥处理，采用实时定量PCR方法测定微生物N循环功能基因丰度，并估算微生物N转化遗传潜力.结果表明，与NPK处理相比，有机物料添加显著增加了参与有机N分解、N固定和N还原的异养微生物数量，而降低了执行氨氧化的自养微生物丰度.因此，异养微生物的比例增加，自养微生物的比例降低.施肥措施变化显著提高了微生物N存储和气态N排放潜力，降低了NO₃^-淋溶潜力，N₂ O还原潜力也有所提升.基于距离的冗余分析（db-RDA）表明，5种施肥处理间N循环功能基因丰度差异显著（PERMANOVA，P=0.002），NH₄⁺是驱动这种变化的关键因子，施用有机肥有利于异养N循环功能微生物，并且同时加入秸秆增强了这种影响.Pearson相关分析表明N存储潜力和气态N排放潜力均与NH₄⁺含量显著负相关；NO₃^-淋溶潜力与SOC和TN含量显著负相关，而与NH₄⁺含量显著正相关.综上所述，在化肥减量基础上添加有机物料有利于增加农田土壤N库，降低土壤N淋溶损失，甚至在特定环境下可以降低N₂ O排放的环境风险.

Impacts of Co-application of Chemical Fertilizer Reduction and Organic Material Amendment on Fluvo-aquic Soil Microbial N-cycling Functional Gene Abundances and N-converting Genetic Potentials in Northern China

The emerging environment-associated issues due to the overuse of inorganic fertilizers in agricultural production are of global concern despite the benefit of high yields. Eco-friendly organic materials with the capability to fertilize soil are encouraged to partially replace mineral fertilizer. The N cycle conducted by soil microorganisms is the most important biogeochemical process, dictating the N bioavailability in farmland ecosystems; however, little is known about how organic material amendment affects soil microbial N cycling under chemical fertilizer reduction. Hence, a fixed field trial with five fertilization practices was implemented to experimentally alter microorganisms essential for the soil N cycle, including conventional chemical fertilization (NPK), reduced chemical fertilization (NPKR), reduced chemical fertilization plus straw (NPKRS), reduced chemical fertilization plus organic fertilizer (NPKRO), and reduced chemical fertilization plus organic fertilizer and straw (NPKROS). The microbial N-cycling gene abundances and associated N-converting genetic potentials were evaluated using real-time quantitative PCR. In comparison to conventional chemical fertilization (NPK), organic addition significantly increased the amounts of heterotrophic microbes involved in organic N decomposition, N fixation, and N reduction; however, it reduced autotrophic microbes performing ammonia oxidization. Consequently, the overall proportion of heterotrophic microbes was remarkably enhanced, and the autotrophic proportion was correspondingly lowered. The fertilization practice shift significantly improved N fixation and gaseous N emission potentials, whereas it suppressed NO₃^- leaching potential. A significant discrepancy among five fertilization treatments was observed based on functional gene abundances (PERMANOVA, P=0.002),as revealed by distance-based redundancy analysis (db-RDA), with NH₄⁺ as the dominant factor. Organic fertilizer addition was beneficial for heterotrophic N functional microorganisms, with simultaneous input of straw augmenting such an effect. Pearson''s correlation analysis revealed that N storage and gaseous N emission potentials were both substantially negatively correlated with NH₄⁺; NO₃^- leaching potential was notably negatively associated with SOC and TN but significantly related to NH₄⁺. In conclusion, chemical fertilizer reduction combined with organic material amendments, a main fertilization recommendation, may enhance soil N storage, diminish N loss by leaching, and mitigate the environmental risk of N₂O emission. This deserves attention considering that healthy and sustainable agricultural soil environment can be cultivated from the view of microbial N-cycling.