Nitrogen (N) fertilization is the major contributor to nitrous oxide (N₂O) emissions from agricultural soil, especially in post‐harvest seasons. This study was carried out to investigate whether ryegrass serving as cover crop affects soil N₂O emissions and denitrifier community size. A microcosm experiment was conducted with soil planted with perennial ryegrass (Lolium perenne L.) and bare soil, each with four levels of N fertilizer (0, 5, 10 and 20 g N m⁻²; applied as calcium ammonium nitrate). The closed‐chamber approach was used to measure soil N₂O fluxes. Real‐time PCR was used to estimate the biomass of bacteria and fungi and the abundance of genes involved in denitrification in soil. The results showed that the presence of ryegrass decreased the nitrate content in soil. Cumulative N₂O emissions of soil with grass were lower than in bare soil at 5 and 10 g N m⁻². Fertilization levels did not affect the abundance of soil bacteria and fungi. Soil with grass showed greater abundances of bacteria and fungi, as well as microorganisms carrying narG, napA, nirK, nirS and nosZ clade I genes. It is concluded that ryegrass serving as a cover crop holds the potential to mitigate soil N₂O emissions in soils with moderate or high NO₃⁻ concentrations. This highlights the importance of cover crops for the reduction of N₂O emissions from soil, particularly following N fertilization. Future research should explore the full potential of ryegrass to reduce soil N₂O emissions under field conditions as well as in different soils.

中文翻译：

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黑麦草作为农作物的潜力，可减少土壤N2O排放并增加反硝化细菌的种群规模

氮肥是造成农业土壤中一氧化二氮（N ₂ O）排放的主要因素，特别是在收获后季节。进行了这项研究，以调查黑麦草作为覆盖作物是否会影响土壤N ₂ O排放和反硝化菌群落的大小。用多年生黑麦草（黑麦草）种植的土壤和裸露的土壤进行了微观实验，每种土壤都施用四种氮肥水平（0、5、10和20 g N m ^-2；用作硝酸钙铵）。密闭室法用于测量土壤N ₂O通量。实时荧光定量PCR用于估算细菌和真菌的生物量以及土壤中反硝化所涉及的基因的丰度。结果表明，黑麦草的存在降低了土壤中的硝酸盐含量。在5和10 g N m ^-2时，草的土壤累积N ₂ O排放低于裸露的土壤。施肥水平不影响土壤细菌和真菌的丰度。有草的土壤显示出更多的细菌和真菌，以及携带narG，napA，nirK，nirS和nosZ进化枝I基因的微生物。结论是黑麦草作为覆盖作物具有缓解土壤N ₂的潜力。O排放在中度或高NO土壤₃ ^-的浓度。这突出了覆盖作物对于减少土壤中N ₂ O排放的重要性，特别是在施氮后。未来的研究应探索黑麦草在田间条件下以及不同土壤中减少土壤N ₂ O排放的全部潜力。