Mitigation of NO emissions, a potent greenhouse gas, remain challenging due to knowledge gaps in plant-mediated nitrogen (N) transformation pathways, which limits ability to identify optimal approaches for efficient N utilization. We set up mesocosms with barley, Italian ryegrass, and barley in combination with Italian ryegrass to assess role of cover crop in NO emission mitigation. Soil emitted NO was collected simultaneously from the pots with plants at three growth stages: namely, vegetative, canopy expansion, and grain filling. The gas sample NO contents, N in microbial biomass (MBN), mineral N content, and phospholipid fatty acid (PLFA) analysis in soils were determined at the three growth stages. Cumulatively, highest NO was emitted from soil under Italian ryegrass (0.056 mg N g soil) followed by barley (0.0051 mg N g soil) and the least under barley and Italian ryegrass combination (0.0014 mg N g soil). The high emissions under Italian ryegrass occurred at vegetative stage due to high reactive N availability. Strong emissions were observed at canopy expansion stage under barley and were linked to access to the large mineral N proportion redistributed to the lower depth as depicted by highest MBN (0.025 mg N g soil) and decreased extractable N (0.0068 mg N g soil). The high emissions under barley correlated with high fungal/bacterial ratio, pointing towards a fungal role in the emissions. The least soil NO emissions under barley and Italian ryegrass combination were accompanied by elimination of variations induced by the plant growth stages. Absence of fungal PLFA biomarker under barley and Italian ryegrass combination indicates a potential inhibition and corresponds with reduced NO emissions. Together, these results broaden our understanding on how plant-soil interactions drives NO emissions processes and improves our ability to identify optimal plant-based emission mitigation approaches.

中文翻译：

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植物物候调节和播种覆盖作物减少 N2O 排放


由于植物介导的氮（N）转化途径方面的知识差距，减少二氧化氮（一种强效温室气体）的排放仍然具有挑战性，这限制了确定有效氮利用的最佳方法的能力。我们建立了大麦、意大利黑麦草以及大麦与意大利黑麦草组合的中生态系统，以评估覆盖作物在减少 NO 排放方面的作用。从盆中同时收集处于三个生长阶段的植物的土壤排放的NO：即营养期、冠层扩张期和灌浆期。在三个生长阶段测定了气体样品中的 NO 含量、微生物量 (MBN) 中的 N、矿物质 N 含量以及土壤中的磷脂脂肪酸 (PLFA) 分析。累积起来，意大利黑麦草下的土壤排放的 NO 最高（0.056 mg N·g 土壤），其次是大麦（0.0051 mg N·g 土壤），大麦和意大利黑麦草组合下的 NO 排放量最少（0.0014 mg N·g 土壤）。由于活性氮利用率高，意大利黑麦草的高排放发生在营养阶段。在大麦下的冠层扩张阶段观察到强烈的排放，并与获得大量矿物质氮比例重新分配到较低深度有关，如最高 MBN（0.025 mg N·g 土壤）和减少的可提取氮（0.0068 mg N·g 土壤）所示。大麦下的高排放量与高真菌/细菌比率相关，表明真菌在排放量中发挥了作用。大麦和意大利黑麦草组合的土壤氮氧化物排放量最低，同时消除了植物生长阶段引起的变化。大麦和意大利黑麦草组合下缺乏真菌 PLFA 生物标志物表明存在潜在的抑制作用，并且与 NO 排放量的减少相对应。 总之，这些结果拓宽了我们对植物与土壤相互作用如何驱动二氧化氮排放过程的理解，并提高了我们确定基于植物的最佳减排方法的能力。