Introducing cover crops in monocropping systems to improve soil health has been broadly adopted worldwide. However, the impacts of different cover cropping systems on soil emissions and related soil fractions and their regulatory mechanism remain elusive. In this study, four cropping systems, i.e., relay intercropping with Orychophragmus violaceus L./cotton (OvC), Vicia villosa Roth/cotton (VvC), a cover crop mixture (Ov and Vv)/cotton (MSC) and a fallow field–cotton (FFC) system, were combined with four N application rates in a two-rotation cycle (2019–2021) to evaluate the effects on soil greenhouse gases (GHGs) emission, ammonia (NH₃) volatilization, and labile carbon (C) and nitrogen (N) fractions and their relationships. Compared with the FFC system, the cumulative NH₃ volatilization and nitrous oxide (N₂O) emissions of OvC are noticeably reduced 13% and 58%, respectively, and those of VvC are comparable, while those of MSC are markedly increased by 15% and 24%, respectively. N fertilization significantly affects soil NH₃ volatilization and N₂O emissions, and a higher N rate results in more gaseous N emissions. In addition, NH₃ volatilization and N₂O emission are positively correlated with the soil microbial biomass N (MBN), dissolved organic N (DON), NH₄⁺-N and NO₃^--N but negatively correlated with microbial biomass C (MBC) and dissolved organic C (DOC). OvC system decreased gaseous N emission by high soil MBC/MBN ratio, Vv as cover crop indirectly promote soil N₂O emission through increased soil MBN, DON and MBC content, while cover crop mixtures increase soil labile C and N fractions and enhance gaseous N emission ultimately. Overall, application of N fertilizer and cover crop mixture both promoted soil NH₃ and N₂O emissions; the relay intercropping nonlegume cover crop Ov noticeably mitigates N₂O and NH₃ emissions through an increase in the soil MBC and reduce in the labile N, while introduction of the legume cover crop Vv increases N₂O emissions but reduces soil NH₃ volatilization due to a lower soil MBC/MBN ratio.

在单一种植系统中引入覆盖作物以改善土壤健康已在世界范围内广泛采用。然而，不同覆盖种植系统对土壤排放和相关土壤组分的影响及其调控机制仍然难以捉摸。在这项研究中，四种种植系统，即与Orychophragmus violaceus L./cotton (OvC)、Vicia villosa Roth/cotton (VvC)、覆盖作物混合物（Ov和Vv）/棉花（MSC）和休耕地的套作-棉花 (FFC) 系统，在两个轮换周期（2019-2021 年）中与四种施氮量相结合，以评估对土壤温室气体 (GHG) 排放、氨 (NH ₃) 挥发，以及不稳定的碳 (C) 和氮 (N) 分数及其关系。与FFC系统相比，OvC的累积NH ₃挥发量和一氧化二氮（N ₂ O）排放量分别显着降低13%和58%，与VvC不相上下，MSC显着增加15%和 24%，分别。施氮肥显着影响土壤NH ₃挥发和N ₂ O排放，施氮量越高，气态氮排放越多。此外，NH ₃挥发和N ₂ O排放与土壤微生物量N（MBN）、溶解有机N（DON）、NH ₄ ⁺ -N和NO呈正相关。₃ ^- -N 但与微生物量 C (MBC) 和溶解有机 C (DOC) 呈负相关。OvC 系统通过提高土壤 MBC/MBN 比值降低气态 N 排放，作为覆盖作物的 Vv 通过增加土壤 MBN、DON 和 MBC 含量间接促进土壤 N ₂ O 排放，而覆盖作物混合物增加土壤不稳定 C 和 N 组分并增加气态 N最终排放。总体而言，氮肥和覆盖作物混合物的施用均促进了土壤NH ₃和N ₂ O的排放；间作非豆科覆盖作物 Ov通过增加土壤 MBC 和减少不稳定 N显着减轻 N ₂ O 和 NH _{3排放，而引入豆科覆盖作物 Vv 增加 N2} O 排放，但由于较低的土壤 MBC/MBN 比率，减少了土壤 NH _3挥发。