Agricultural activities are potential sources of greenhouse gas (GHG) emissions, and nitrous oxide (N₂O) is one of the most important non-carbon-dioxide GHGs. Perennial legumes such as alfalfa (Medicago sativa L.) have potential roles for reduction of soil GHG emissions as part of crop rotation systems. However, the implications of perennial legume termination by tillage and subsequent soil incorporation of the residues for reduced GHG emissions have been poorly examined in Mediterranean environments. With the aim to assess the magnitude of soil N₂O emissions (important for the definition of mitigation strategies) after perennial legume termination in alfalfa-wheat crop rotation systems in a Mediterranean environment, we defined the hypothesis that alfalfa termination by tillage with incorporation of the crop residues will increase soil N₂O emissions during the subsequent wheat season. To test this hypothesis, closed static chambers were used in a field–plot experiment, using a complete randomised block design with three replicates. Soil N₂O emissions were monitored across 33 sampling dates from October 2017 to July 2018, as a comparison between an original 6-year-old alfalfa field (‘continuous alfalfa’) and alfalfa termination followed by wheat (‘alfalfa+ wheat’). The soil N₂O emission fluxes varied markedly across the treatments and throughout the monitoring period (from – 0.02±0.01 to 0.53±0.14 g N-N₂O ha^–1 h^–1, and from 0.02±0.07 to 0.37±0.11 g N-N2O ha^–1 h^–1 for continuous alfalfa and alfalfa+wheat, respectively), generally following the changes in soil temperature. Several soil N₂O emission peaks were recorded for both treatments, which mainly coincided with rainfall and with increased soil water content. In the 2 months following alfalfa termination, alfalfa+wheat showed higher cumulative weekly soil N₂O emissions compared to continuous alfalfa. Following alfalfa termination for alfalfa+wheat, the increased cumulative weekly soil N₂O emissions appeared to be due to asynchrony between nitrogen (N) released into the soil from mineralisation of the alfalfa residues and N uptake by the wheat. Despite these initial high soil N₂O emissions for alfalfa+wheat, the seasonal cumulative soil N₂O emissions were not significantly different (0.77±0.09 vs 0.85±0.18 kg N-N₂O ha^–1 for continuous alfalfa and alfalfa+wheat, respectively). These data suggest that legume perennial crop termination in alfalfa–wheat rotation systems does not lead to significant loss of N₂O from the soil. The alfalfa termination by tillage performed in autumn might, on the one hand, have slowed the mineralisation process, and might, on the other hand, have synchronised the N release by the mineralised crop residues, with the N uptake by the wheat reducing the soil N₂O emissions.

农业活动是温室气体（GHG）排放的潜在来源，而一氧化二氮（N ₂ O）是最重要的非二氧化碳温室气体之一。多年生豆科植物，如苜蓿（苜蓿（Medicago sativa L.））作为减少作物轮作系统的一部分，具有减少土壤温室气体排放的潜在作用。然而，在地中海环境中，人们对通过耕作终止多年生豆类植物以及随后将残留物掺入土壤对减少温室气体排放的影响的研究很少。为了评估土壤N ₂的大小在地中海环境中苜蓿-小麦作物轮作系统中多年生豆类植物终止后的O排放（对于缓解策略的定义很重要），我们定义了以下假设：在耕作过程中苜蓿终止并掺入作物残渣会增加土壤N ₂ O排放随后的小麦季节。为了验证这一假设，在现场绘图实验中使用了封闭的静态腔室，使用了完整的随机区组设计并进行了三个重复。从2017年10月到2018年7月的33个采样日期对土壤N ₂ O排放进行了监测，以比较原始的6年历史的紫花苜蓿田（``连续紫花苜蓿''）和紫花苜蓿终止条件，然后是小麦（``紫花苜蓿+小麦''）。土壤N ₂在整个处理期间和整个监测期间，O排放通量变化显着（从– 0.02±0.01到0.53±0.14 g NN ₂ O ha ^–1 h ^–1，从0.02±0.07到0.37±0.11 g N-N2O ha ^–1 h ^–1分别代表连续的苜蓿和苜蓿+小麦，通常随土壤温度的变化而变化。两种处理均记录到多个土壤N ₂ O排放峰，这主要与降雨和土壤含水量增加相吻合。紫花苜蓿终止后的2个月中，紫花苜蓿+小麦的累积每周土壤N ₂含量更高与连续苜蓿相比，O排放量大。在苜蓿+小麦终止苜蓿之后，每周累积的土壤N ₂ O排放增加似乎是由于苜蓿残渣矿化释放到土壤中的氮（N）与小麦吸收氮之间的异步性所致。尽管紫花苜蓿+小麦最初出现较高的土壤N ₂ O排放量，但连续苜蓿和紫花苜蓿+小麦的季节性累积土壤N ₂ O排放没有显着差异（分别为0.77±0.09和0.85±0.18 kg NN ₂ O ha ^–1）。这些数据表明，苜蓿-小麦轮作系统中豆科植物多年生作物的终止不会导致N _2的大量损失。O来自土壤。秋季通过耕种终止苜蓿可能一方面减缓了矿化过程，另一方面可能使矿化的农作物残留的氮释放与小麦的氮吸收减少了土壤的同步化。 N ₂ O排放。