Adding nitrogen fertilizers to agricultural soils contributes to increasing concentrations of nitrous oxide (N2 O) in the atmosphere. However, the impacts of N addition on soil organic matter (SOM) turnover, SOM availability, and the ensuing SOM-derived N2 O emissions remain elusive. Within this context, the net change in direction and rate of SOM-derived N2 O production triggered by added N is termed the N2 O priming effect. This incubation study examined the sources and priming of N2 O production as a function of urea addition and multiple moisture contents in a soil with high SOM (55 g organic C kg-1 ). We assessed four water-filled pore space (WFPS) conditions: 28, 40, 52, and 64%. Relative to controls receiving no N, urea addition increased N2 O production by 2.6 times (P < 0.001). Cumulative N2 O production correlated well with nitrification rates (r = 0.75, P = 0.03). We used 15 N-labelled urea to trace the added urea into N2 O. Of the N added via urea, the recovery as N2 O-N shifted from 0.02 to 0.17% when WFPS increased from 28 to 64% (P < 0.05). We also partitioned the N2 O production into urea versus SOM sources. More N2 O was sourced from SOM than urea, with 59 ± 2% N2 O originating from SOM. The magnitude of SOM-derived N2 O under urea was larger than that of the control, revealing that positive N2 O priming was triggered by urea addition. Upon subtracting the controls, the primed N2 O was a consistent 19 ± 2% of the total N2 O produced by urea-amended soils. Nevertheless, the priming magnitude rose sharply with increasing moisture by more than one order of magnitude from 4 to 48 μg N2 O-N kg-1 soil, and in exponential mode (R2 = 0.98). Soil moisture, SOM, and nitrification interacted to drive the sources and priming of N2 O. This article is protected by copyright. All rights reserved.

中文翻译：

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高有机质土壤中一系列水分含量的 N 2 O 产生的来源和启动

向农业土壤中添加氮肥会增加大气中一氧化二氮 (N2 O) 的浓度。然而，氮添加对土壤有机质 (SOM) 周转率、SOM 可用性以及随后 SOM 衍生的 N2 O 排放的影响仍然难以捉摸。在这种情况下，由添加 N 触发的 SOM 衍生 N2 O 产生的方向和速率的净变化称为 N2 O 引发效应。该孵化研究检查了 N2 O 产生的来源和启动，作为具有高 SOM（55 g 有机 C kg-1 ）的土壤中尿素添加和多种水分含量的函数。我们评估了四种充满水的孔隙空间 (WFPS) 条件：28%、40%、52% 和 64%。相对于不接受 N 的对照，添加尿素使 N2 O 产量增加了 2.6 倍（P < 0.001）。累积 N2 O 产量与硝化速率密切相关 (r = 0.75, P = 0.03)。我们使用 15 N 标记的尿素来追踪添加到 N2 O 中的尿素。在通过尿素添加的 N 中，当 WFPS 从 28% 增加到 64% 时，N2 ON 的回收率从 0.02% 变为 0.17% (P < 0.05)。我们还将 N2 O 生产划分为尿素和 SOM 来源。来自 SOM 的 N2 O 多于尿素，其中 59 ± 2% 的 N2 O 来自 SOM。尿素下 SOM 衍生的 N2 O 的量级大于对照，表明正 N2 O 引发是由尿素添加触发的。减去对照后，经过处理的 N2 O 是尿素修正土壤产生的 N2 O 总量的 19 ± 2%。尽管如此，随着水分从 4 到 48 μg N2 ON kg-1 土壤增加一个数量级以上，引发量级急剧上升，和指数模式 (R2 = 0.98)。土壤水分、SOM 和硝化作用相互作用以驱动 N2 O 的来源和引发。本文受版权保护。版权所有。