In agroecosystems, efficient fertilizer use is key to optimizing productivity and reducing nutrient losses that can be detrimental for the environment, such as nitrous oxide (N₂O) emissions. Because microbial communities regulate nitrogen (N) fate in soils, some agrochemicals inhibit specific transformations to reduce N losses. Our study aimed to describe short-term dynamics of N-cycling genes and transcripts and N₂O emissions after fertilization with urea-ammonium nitrate (UAN) with or without the addition of nitrification plus urease inhibitors (NUI). The experiment consisted of 4-ha corn plots located in SE Ontario, Canada, where field-scale N₂O emissions were monitored continuously using micro-meteorological techniques. Soil samples (0–10 cm) were taken 10 days before (baseline) and 2, 6, 9, 13 and 16 days after fertilization, and immediately flash-frozen. We co-extracted DNA and RNA and, using real-time PCR, quantified genes/transcripts targeting total bacteria (16S rRNA) and key N-cycling groups: ureolytic (ureC), ammonia-oxidizers (bacterial/archaeal amoA), nitrite-reducers (nirK/nirS) and N₂O-reducers (clade I/II nosZ). The addition of NUI did not prevent an N₂O flux event but reduced its duration and magnitude by more than 50%, and net cumulative N₂O emissions for the sampling period by ~68%. NUI effects on N-cycling microorganisms were evident on day 9, as a transient reduction (40–56%) of ammonia-oxidizers and denitrifiers. Changes in transcripts were minor and only detectable on ureC (day 2), nirS and clade II nosZ (day 9). NUI did not interfere with temporal fluctuations in nirK and nirS, but it differentially affected nosZ response to a later rainfall event. Unexpectedly, N₂O emissions were negatively associated with the ratio between nitrite-reducers and N₂O-reducers. NUI effects on N-cycling microorganisms were minor and transient but resulted in a field-scale reduction in N₂O emissions, possibly due to a combination of environmental factors and legacy effects from previous years of treatment.

在农业生态系统中，有效使用肥料是优化生产力和减少可能对环境有害的营养物质流失的关键，例如一氧化二氮（N ₂ O）排放。由于微生物群落控制着土壤中的氮（N）命运，因此某些农药会抑制特定的转化以减少氮的损失。我们的研究旨在描述在添加或不添加硝化作用和脲酶抑制剂（NUI）的条件下，尿素-硝酸铵（UAN）施肥后N循环基因和转录本以及N ₂ O排放的短期动态。该实验由位于加拿大东南安大略的4公顷玉米田组成，田间规模为N ₂使用微气象技术连续监测O排放量。在施肥前（基线）第10天和施肥后第2、6、9、13和16天采集土壤样品（0-10厘米），并立即速冻。我们共提取了DNA和RNA，并使用实时PCR定量了针对总细菌（16S rRNA）和关键N循环基团的基因/转录本：尿素分解（ureC），氨氧化剂（细菌/古细菌amoA），亚硝酸盐-还原剂（nirK / nirS）和N ₂ O还原剂（clad I / II nosZ）。NUI的添加不能防止N ₂ O通量事件的发生，但会减少其持续时间和幅度，降低幅度超过50％，并且净累积N ₂采样期间的O排放量降低了约68％。NUI对N循环微生物的影响在第9天就很明显，因为氨氧化剂和反硝化剂的瞬时减少（40-56％）。笔录变化很小，仅在ureC（第2天），nirS和clade II nosZ（第9天）时可检测到。NUI不会干扰nirK和nirS的时间波动，但会差异地影响nosZ对以后降雨事件的响应。出乎意料的是，N ₂ O排放与亚硝酸盐还原剂和N ₂之间的比率负相关O型减速器。NUI对N循环微生物的影响较小且短暂，但可能导致环境规模的N ₂ O排放减少，这可能是由于环境因素和前几年治疗的遗留影响共同作用的结果。