The response of nitrifier and denitrifier populations and associated N2O emissions to different carbon-to-nitrogen (C/N = 17 or 45) straw amendments was monitored under flooding-drying and non-flooding conditions. A 10-week laboratory mesocosm study was conducted in two soils, (i) a paddy soil with a long history of managed flooding-drying (CN), and (ii) a wheat cropping soil with no previous history of flooding (UK). We measured N2O fluxes and the abundances of ammonia-oxidizing archaea (AOA) and bacteria (AOB), nitrite reductase (nirK and nirS) genes, and nitrous oxide reductase (nosZI and nosZII) genes during flooding (4 weeks) and post-flooding (6 weeks). Straw addition enhanced N2O emissions, with higher fluxes apparent after incorporation of narrow C/N residues. Moreover, the impact of crop amendment on N2O emission was exacerbated when soil was under flooding-drying conditions. The abundances of nirS and nosZI genes in CN soil and AOA gene in UK soil were increased by straw amendment, with highest in narrow C/N straw amendments. Structural equation modeling showed that the impact of denitrifier gene abundance on the N2O flux was stronger than that of nitrifier gene abundance in the two soils, and significant correlations were observed between N2O fluxes and the consumption of DOC and NO3−, indicating that denitrification was the dominant N2O production pathway during the drying phase. The ratio of (nirS + nirK)/(nosZI + nosZII) in the narrow C/N amendment was greater than in the wide C/N treatment after flooding, suggesting that the straw C/N ratio had an effect on the capacity for N2O production via denitrification. We conclude that crop amendments with an appropriate C/N ratio could minimize N2O fluxes through regulating the denitrification process when soils are subjected to regular flooding and drying and also experiencing greater frequencies of flooding.

中文翻译：

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作物残渣碳氮比调节洪水后反硝化剂 N2O 的产生

在淹水-干燥和非淹水条件下监测硝化菌和反硝化菌种群以及相关的 N2O 排放对不同碳氮 (C/N = 17 或 45) 秸秆添加物的响应。一项为期 10 周的实验室中观研究在两种土壤中进行，(i) 具有长期管理洪水-干燥 (CN) 历史的稻田，和 (ii) 以前没有洪水历史的小麦种植土壤（英国）。我们测量了洪水期间（4 周）和洪水后的 N2O 通量以及氨氧化古细菌 (AOA) 和细菌 (AOB)、亚硝酸盐还原酶（nirK 和 nirS）基因以及一氧化二氮还原酶（nosZI 和 nosZII）基因的丰度（6 周）。秸秆添加增加了 N2O 排放，在掺入窄 C/N 残留物后明显有更高的通量。而且，当土壤处于淹干条件时，作物改良剂对 N2O 排放的影响会加剧。秸秆改良增加了 CN 土壤中 nirS 和 nosZI 基因和英国土壤中 AOA 基因的丰度，其中窄 C/N 秸秆改良的丰度最高。结构方程模型表明，两种土壤中反硝化菌基因丰度对 N2O 通量的影响强于硝化菌基因丰度，且 N2O 通量与 DOC 和 NO3− 消耗量之间存在显着相关性，表明反硝化作用是在干燥阶段占主导地位的 N2O 生产途径。(nirS + nirK)/(nosZI + nosZII) 的比值在窄 C/N 修正中大于宽 C/N 处理后驱水处理，表明秸秆 C/N 比对通过反硝化产生 N2O 的能力有影响。我们得出的结论是，当土壤受到定期洪水和干燥以及经历更大频率的洪水时，具有适当 C/N 比的作物改良剂可以通过调节反硝化过程来最小化 N2O 通量。