Emissions of nitrous oxide (N₂O), a potent greenhouse gas, from farmland have been recognized to be affected by soil pH and nitrogen (N) fertilizer application. However, the interactive effects of soil pH and N fertilizer type on N₂O emissions and their influencing mechanism are poorly understood. A field experiment was conducted to elucidate the impacts of synthetic fertilizer and manure on soil properties and N₂O fluxes along a soil acidity gradient (soil pH = 6.8, 6.1, 5.2, and 4.2) in the Huai River Basin, and a lab incubation experiment was performed to understand the underlying mechanisms of changed N₂O flux. Low soil pH inhibited the ammonia-oxidizing bacteria abundance and thereby reduced the N₂O production by nitrification under both synthetic fertilizer and manure application. The N₂O production by denitrification was also reduced with declining soil pH, likely due to the decreased nirS and nirK abundances, and lower NO₃⁻. However, low soil pH reduced the nosZ abundance and increased (nirS + nirK)/nosZ ratio, resulting in the increased N₂O/(N₂O + N₂) ratio. Finally, with the decreased nitrification and denitrification, soil N₂O emission was significantly reduced with declining soil pH regardless of fertilizer types. Compared with synthetic fertilizer, manure application increased soil nutrients (total N, dissolved organic C, and NO₃⁻), nirK abundance, and (nirS + nirK)/nosZ ratio in the soils with pH of 5.2 and 4.2, thereby promoting N₂O production by denitrification and N₂O/(N₂O + N₂) product ratio in acidic soils. Consequently, soil N₂O emission was increased with manure application in acidic soils. This study provides novel insight and improves our understanding of how soil pH regulates nitrification, denitrification, and N₂O emissions from soils amended with chemical fertilizer and manure, which gives guidance on developing N management strategies for sustainable production and N₂O mitigation in acid soils.

人们已经认识到，农田中一氧化二氮 (N _{2 O) 的排放量受到土壤 pH 值和氮 (N) 肥料施用的影响，一氧化二氮 (N 2 O) 是一种强效温室气体。}然而，土壤pH值和氮肥类型对N ₂ O排放的交互影响及其影响机制尚不清楚。为了阐明合成肥料和厩肥对淮河流域土壤酸度梯度（土壤pH = 6.8、6.1、5.2和4.2）土壤性质和N _{2 O通量的影响进行了田间试验，并进行了实验室培养进行实验是为了了解 N 2} O 通量变化的根本机制。低土壤pH值抑制了氨氧化细菌的丰度，从而减少了合成肥料和粪肥施用下硝化作用产生的N _{2 O。}反硝化产生的N ₂ O 也随着土壤 pH 值的下降而减少，这可能是由于nirS和nirK丰度的减少以及 NO ₃ ^-的降低。然而，低土壤pH值降低了nosZ丰度并增加了( nirS + nirK )/ nosZ比率，导致N ₂ O/(N ₂ O + N ₂ )比率增加。最后，随着硝化作用和反硝化作用的减少，无论肥料类型如何，土壤N ₂ O排放量随着土壤pH值的下降而显着减少。与化肥相比，施用粪肥增加了pH 5.2和4.2土壤中的土壤养分（全氮、溶解性有机碳和NO ₃ ^-）、nirK丰度和（nirS + nirK）/ nosZ比，从而促进N ₂酸性土壤中反硝化产生的 O 和 N ₂ O/(N ₂ O + N _{2 ) 产品比率。}因此，酸性土壤中施肥会增加土壤N _{2 O 排放量。}这项研究提供了新的见解，提高了我们对土壤pH如何调节化肥和粪肥改良土壤中的硝化、反硝化和N ₂ O排放的理解，为制定可持续生产和酸性环境中N ₂ O减排的氮管理策略提供了指导土壤。