菜地氨氧化微生物驱动的N2O和NO对有机无机肥配施的响应

氨氧化细菌（AOB）和氨氧化古菌（AOA）是驱动土壤氨氧化过程的"引擎".氨氧化过程在土壤氧化亚氮（N₂O）和一氧化氮（NO）排放过程中扮演着重要角色.有机无机肥配施是实现化肥零增长和作物稳产增产的重要途径,但在有机无机肥配施下,菜地土壤AOB和AOA对氨氧化过程的相对贡献仍不清楚.本研究采用选择性抑制的方法（辛炔和乙炔）区分有机肥添加近3年后（2016年10月—2019年5月）AOB和AOA在氨氧化过程中对碱性菜地土壤N₂O和NO产生的相对贡献.试验共设5种施肥处理：不施氮肥（CK）、单施尿素（N）、单施有机肥（M）、50%尿素+50%有机肥（M1N1）和80%尿素+20%有机肥（M1N4）.结果表明,有机无机肥配施（M1N1和M1N4）可显著增加土壤电导率、有机碳和全氮含量.培养试验发现,与N处理相比,M和M1N1处理分别使N₂O排放量增加100.7%和38.8%,NO排放量增加77.9%和42.8%,AOB基因丰度增加16.6%和10.2%,同时,AOB对N₂O排放的相对贡献增加6.5%.相反,M1N4处理分别使N₂O和NO排放量降低19.3%和4.8%,AOB基因丰度降低37.5%,同时,AOB对N₂O及NO排放的相对贡献分别降低7.8%和7.4%.相关分析表明,土壤N₂O和NO累积排放量与土壤AOB基因丰度呈显著正相关（p<0.05）,与土壤AOA基因丰度无显著相关性.有机无机肥配施下AOB是氨氧化过程的主要驱动者,适当比例的有机无机肥配施（即M1N4）措施可在一定程度上减弱AOB对碱性菜地土壤N₂O及NO排放的相对贡献.

Responses of N2O and NO emissions driven by ammonia-oxidizing bacteria and archaea to different combinations of organic and inorganic N fertilization in a vegetable field

Ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) are the engines of soil ammonia oxidation. The ammonia oxidation process plays an important role in the emissions of nitrous oxide (N₂O) and nitric oxide (NO) from the soil. The combined application of organic and inorganic nitrogen (N) fertilizers is an important way to achieve zero growth of chemical N fertilizer application and stable crop yields. However, the relative contribution of AOB and AOA to ammonia oxidation in vegetable soil is still unclear. In this study, the relative contribution of AOB and AOA to N₂O and NO emissions from an alkaline vegetable soil was investigated by the inhibitor technology (octyne+acetylene) after three years of combined application of organic and inorganic N fertilizers (from October 2016 to May 2019). In the field experiment, five treatments were set up as follows: no N application (CK), only urea N (N), only organic N fertilizer (M), 50% urea+50% organic N fertilizer (M1N1), and 80% urea+20% organic N fertilizer (M1N4). The combined application of organic and inorganic N fertilizers (M1N1 and M1N4) significantly increased soil EC, SOC, and TN contents. Compared with the N treatment, the M and M1N1 treatments increased N₂O emissions by 100.7% and 38.8%, NO emissions by 77.9% and 42.8%, AOB gene abundance by 16.6% and 10.2%, respectively; and the average relative contribution of AOB to N₂O emissions was increased by 6.5%. To the contrary, relative to the N treatment, the M1N4 treatment reduced N₂O and NO emissions by 19.3% and 4.8%, respectively; reduced AOB gene abundance by 37.5%, and the relative contribution of AOB to N₂O and NO emissions by 7.8% and 7.4%, respectively. Correlation analysis showed that the cumulative emissions of N₂O and NO were positively correlated with the AOB gene abundance (p<0.05), while no correlation with the AOA gene abundance. It''s inferred that the AOB was the main driver of ammonia oxidation in the alkaline vegetable soil under the combined application of organic and inorganic N fertilizers, and the appropriate mixing ratio at M1N4 fertilization could reduce the contribution of AOB to N₂O and NO emissions in this study.