Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) influence the nitrate (NO₃⁻) reduction and its final fate in the environment. However, it is unclear how denitrifying and DNRA bacterial communities respond to different environment conditions. Here, we investigated the effects of fertilization and sampling time (April, July and November) on the abundances of nitrogen (N) cycling genes in processes of denitrification and DNRA at different soil depths (0–20, 20–40 and 40–60 cm) based on a long-term fertilization experiment station (initiated in 1987). The abundances of genes involved in NO₃⁻ reduction process were determined using quantitative PCR (qPCR) analysis method. Sampling time showed a stronger effect on the abundances of denitrifying and DNRA genes than fertilization. And the effect of fertilization on the abundances of genes involved in NO₃⁻ reduction process was decreased with soil depths. Compared with no fertilizer (CK), the application of mineral N fertilizer (N2 and N4) reduced the abundances of denitrification and DNRA genes at 0–20 cm soil depth, regardless of sampling time. However, the application of organic manure combined with mineral N fertilizer (M2N2) clearly increased the abundance of specific denitrifying genes, including napA (NO₃⁻ to NO₂⁻) and nosZ (N₂O to N₂) genes compared with N2 and N4 treatments at 0–20 and 20–40 cm soil depths. Although the abundance of nrfA gene was the highest, the abundance of norB gene was the most sensitive to environmental variation among all the tested N cycling genes. Ratio of NO₃⁻ to ammonium (NO₃⁻/NH₄⁺) was significantly correlated with all the denitrifying and DNRA genes. In general, long-term application of organic manure combined with mineral N fertilizer has a potential to mitigate the NO₃⁻ leaching and N₂O production, and NO₃⁻/NH₄⁺ ratio is an important factor driving the dynamics of bacterial communities involved in the NO₃⁻ reduction process.

反硝化和异化硝酸盐还原为铵 (DNRA) 会影响硝酸盐 (NO ₃ ^- ) 还原及其在环境中的最终归宿。然而，目前尚不清楚反硝化和 DNRA 细菌群落如何响应不同的环境条件。在这里，我们研究了施肥和采样时间（4 月、7 月和 11 月）对不同土壤深度（0-20、20-40 和 40-60 cm）基于长期施肥实验站（1987年启动）。NO _{3 相关}基因的丰度^-还原过程使用定量 PCR (qPCR) 分析方法确定。采样时间对反硝化和 DNRA 基因丰度的影响大于施肥。施肥对参与NO ₃ ^-还原过程的基因丰度的影响随着土壤深度的增加而降低。与不施肥（CK）相比，施用矿物氮肥（N2 和 N4）降低了 0-20 cm 土壤深度处的反硝化和 DNRA 基因的丰度，无论采样时间如何。然而，有机肥结合矿物氮肥（M2N2）的施用明显增加了特定反硝化基因的丰度，包括NAP A（NO ₃ ^-到NO ₂ ^-）和nos Z（N ₂ O 到 N ₂）基因与 N2 和 N4 处理在 0-20 和 20-40 cm 土壤深度的比较。尽管nrf A基因的丰度最高，但在所有测试的N循环基因中，nor B基因的丰度对环境变化最敏感。NO ₃ ^-与铵的比率（NO ₃ ^- /NH ₄ ⁺）与所有反硝化和DNRA基因显着相关。一般来说，长期施用有机肥与矿物氮肥结合有可能减轻 NO ₃ ⁻浸出和 N ₂ O 的产生，以及 NO ₃^- /NH ₄ ⁺比率是推动参与NO ₃ ^-还原过程的细菌群落动态的重要因素。