Oxygen (O₂) is a key factor driving the expression of N-cycle-related functional genes and regulating nitrogenous gas production in the soil. However, how and to what extent the associated gene transcription and corresponding gas kinetics interact with the transition of soil O₂ status caused by N fertilisation, remains poorly understood. In this context, we conducted a robotized incubation experiment using a He/O₂ atmosphere with different amounts of ammonium-based fertiliser (0 (control), 60 (AS₆₀) and 200 mg N kg⁻¹ (NH₄)₂SO₄ (AS₂₀₀)) applied to an agricultural soil with a strong nitrification potential under three different initial O₂ levels (oxic 21%, sub-oxic 3%, and anoxic 0%) over 14 days. Through repeated measurements of N₂O, NO, and N₂ concentrations and kinetics of mineral N following the decline of O₂ concentrations, we found that higher ammonium addition (200 vs. 60 mg N kg⁻¹) caused faster O₂ consumption in the headspace and induced up to 238 times higher net accumulation of N₂O under initially oxic headspace condition. We speculate that this was due to: 1) the rapid transition of O₂ status from oxic to anoxic due to vigorous ammonia oxidation; and 2) the increased N₂O/(N₂O + NO + N₂) ratio of denitrification with higher N addition. The amoA and nosZ gene transcript numbers changed significantly in response to ammonium addition and decreasing O₂ concentration, whereas high-throughput sequencing revealed a significant structural alteration of the soil microbiota along with the transition of O₂ status. Our results highlight that the vigorousness of oxygen depletion in the soil matrix driven by rapid ammonia oxidation is the proximal factor that regulates gas kinetics in high nitrification-potential soil when O₂ diffusion is limited. This implies that practices which reduce hotspots of ammonia oxidation have the potential to mitigate N₂O emissions from nitrifier denitrification and denitrification in agricultural soil.

氧气（O ₂）是驱动氮循环相关功能基因表达和调节土壤中含氮气体产生的关键因素。然而，相关的基因转录和相应的气体动力学如何以及在多大程度上与施氮引起的土壤 O ₂状态的转变相互作用，仍然知之甚少。在这种情况下，我们使用 He/O ₂气氛和不同量的铵基肥料（0（对照）、60（AS ₆₀）和 200 mg N kg ^-1 (NH ₄ ) ₂ SO ₄进行了机器人孵化实验(AS ₂₀₀)) 在三种不同的初始 O ₂水平（含氧 21%、亚氧 3% 和缺氧 0%）下，在 14 天内应用于具有强硝化潜力的农业土壤。通过重复测量 N ₂ O、NO 和 N ₂浓度以及 O ₂浓度下降后矿物 N 的动力学，我们发现较高的铵添加量（200 与 60 mg N kg ^-1）导致更快的 O ₂消耗在最初的有氧顶空条件下，N ₂ O 的净积累量增加了 238 倍。我们推测这是由于：1) O ₂的快速转变由于剧烈的氨氧化，从好氧到缺氧的状态；和 2) N ₂ O/(N ₂ O + NO + N ₂ ) 反硝化的比率随着 N 添加量的增加而增加。的AMOA和nosZ基因转录物数目响应于另外铵和减小ö显著改变₂浓度，而高通量测序揭示了土壤的微生物群的显著结构改变与的O-过渡沿₂状态。我们的结果强调，快速氨氧化驱动的土壤基质中氧耗竭的强度是当 O ₂扩散是有限的。这意味着减少氨氧化热点的做法有可能减少农业土壤中硝化菌反硝化和反硝化作用产生的 N ₂ O 排放。