本研究以华北玉麦轮作农田石灰性土壤为研究对象，针对玉米和小麦季的两次施肥事件，采用¹⁵N气体通量法（¹⁵NGF）对田间原位土壤N₂通量进行为期一周的观测。施用肥料为¹⁵N标记尿素（丰度为99 atom％），施用量为130（玉米季）和150（小麦季）kg N ha^–1；并于施肥后的第一、三和五天（缩写DAF 1、DAF 3和DAF 5）进行模拟灌水，控制灌水后土壤湿度达~60% WFPS。结果显示：当罩箱时间为2、4和6 h时，土壤N₂通量的检测限分别为163–1565、81–485和54–281 μg N m^–2 h^–1。土壤N₂通量为159–2943（平均：811）μg N m^–2 h^–1，98.3%的通量数据高于其检测限（即120个观测数据中仅2个达不到通量检测限）。灌溉时间显著影响玉米季观测期内的土壤N₂平均通量，DAF 3处理较DAF 1和DAF 5处理高约80%（p<0.01）；而在小麦季，不同灌溉时间的N₂通量无差异。而且，玉米季观测期内的N₂通量和氧化亚氮（N₂O）与N₂产物比（N₂O/(N₂O+N₂)）均较小麦季高约65%和11倍（p<0.01）。该差异主要归因于玉米季观测期内更高的土壤湿度、温度和氮底物的有效性，利用反硝化贡献N2排放和N₂O/（N₂O+N2）比值。该研究表明¹⁵NGF方法可应用于原位定量集约化石灰性农田土壤的N₂通量。

Denitrification-induced nitrogen (N) losses from croplands may be greatly increased by intensive fertilization.  However, the accurate quantification of these losses is still challenging due to insufficient available in situ measurements of soil dinitrogen (N₂) emissions.  We carried out two one-week experiments in a maize–wheat cropping system with calcareous soil using the ¹⁵N gas-flux (¹⁵NGF) method to measure in situ N₂ fluxes following urea application.  Applications of ¹⁵N-labeled urea (99 atom%, 130–150 kg N ha⁻¹) were followed by irrigation on the 1st, 3rd, and 5th days after fertilization (DAF 1, 3, and 5, respectively).  The detection limits of the soil N₂ fluxes were 163–1 565, 81–485, and 54–281 μg N m⁻² h⁻¹ for the two-, four-, and six-hour static chamber enclosures, respectively.  The N₂ fluxes measured in 120 cases varied between 159 and 2 943 (811 on average) μg N m⁻² h⁻¹, which were higher than the detection limits, with the exception of only two cases.  The N₂ fluxes at DAF 3 were significantly higher (by nearly 80% (P<0.01)) than those at DAF 1 and 5 in the maize experiment, while there were no significant differences among the irrigation times in the wheat experiment.  The N₂ fluxes and the ratios of nitrous oxide (N₂O) to the N₂O plus N₂ fluxes following urea application to maize were approximately 65% and 11 times larger, respectively (P<0.01), than those following urea application to wheat.  Such differences could be mainly attributed to the higher soil water contents, temperatures, and availability of soil N substrates in the maize experiment than in the wheat experiment.  This study suggests that the ¹⁵NGF method is sensitive enough to measure in situ N₂ fluxes from intensively fertilized croplands with calcareous soils.