Nitrogen-fertilized agricultural soils are major emitters of the potent greenhouse gas nitrous oxide (N₂O). Although soil moisture is known to drive N₂O production, the influence of moisture on the priming effects of labile N additions, which alter the N₂O production from native soil organic matter (SOM), remains understudied. We investigated how moisture impacts N₂O primings, nitrification kinetics, and allocation of N₂O sources between nitrification and denitrification. We evaluated urea additions at five water-filled pore spaces (WFPS): 31, 41, 53, 65, and 78%. Based on δ¹⁵N–N₂O site preference (SP), the denitrification source (encompassing bacterial- and nitrifier-denitrification) amply dominated across all moistures. At moistures >60% WFPS, SP exhibited a narrow range of 1.2–1.6‰, whereas at 31% WFPS, SP rose to 9.4‰ (P < 0.001). These SPs translated into denitrification sourcing consistently four-fifth of the N₂O production in the wettest soils. With drier soils, denitrification gradually decreased, but it still produced three-fifth of the N₂O even at the driest soil (31% WFPS). Based on time courses of ammonium and nitrate concentrations, first-order kinetics (k₁) modelling showed much slower nitrification rates at 31% WFPS (0.1 day⁻¹) than the peak nitrification witnessed consistently at both 65 and 78% WFPSs (1.0 day⁻¹). By using isotopically-labelled urea, we further allocated N₂O production into SOM-N and urea-N sources. In soils receiving urea, SOM-N contribution to N₂O production changed from being 77% in the driest soils to 46% in the wettest soil. Along this aeration-to-moisture gradient, net N₂O priming steadily switched from being negative (−20%) in the driest soils to become positive (+14%) at the wettest soil, and this shifting trajectory intercepted the neutral 0% priming at 60% WFPS. Results indicate that pulse N₂O emissions commonly reported in recently N-fertilized fields are triggered by soil moisture surpassing this threshold, which collectively accelerates positive primings of SOM and denitrification.

氮肥农业土壤是强效温室气体一氧化二氮（N ₂ O）的主要排放者。尽管已知土壤水分会驱动N ₂ O的产生，但是仍然需要研究水分对不稳定的N添加物的引发作用的影响，这些元素改变了天然土壤有机质（SOM）的N ₂ O产生量。我们研究了水分如何影响N ₂ O引发，硝化动力学以及硝化和反硝化之间N ₂ O源的分配。我们评估了五个充水孔隙空间（WFPS）的尿素添加量：31％，41％，53％，65％和78％。基于δ ¹⁵ N-N ₂在站点偏好（SP）中，反硝化源（包括细菌和硝化剂的反硝化作用）在所有水分中占主导地位。水分> 60％WFPS时，SP表现出1.2-1.6‰的窄幅变化，而水分含量> 31％WFPS时，SP上升至9.4‰（P <0.001）。这些SP转化为反硝化作用，在最湿的土壤中始终产生五分之四的N ₂ O产量。在较干燥的土壤中，反硝化作用逐渐降低，但即使在最干燥的土壤（31％WFPS）下，N ₂ O仍产生五分之三。基于铵盐和硝酸盐浓度的时程，一阶动力学（k ₁）模型显示在31％WFPS时（0.1天^−1时）硝化速率要慢得多），则在65％和78％的WFPS（1.0天^-1）下，硝化峰值始终如一。通过使用同位素标记的尿素，我们进一步将N ₂ O产量分配到SOM-N和尿素N来源中。在接受尿素的土壤中，SOM-N对N ₂ O产生的贡献从最干燥的土壤的77％变为最湿的土壤的46％。沿着该通气-湿度梯度，净N ₂ O灌注从最干燥的土壤中的负（-20％）稳定地切换为最湿的土壤中的正（+ 14％），并且该移动轨迹截取了中性0％以60％的WFPS启动。结果表明脉冲N ₂近来氮肥田间普遍报告的O排放是由土壤水分超过该阈值触发的，这共同加速了SOM和反硝化的积极启动。