[Objectives] Amendment of biochar significantly affected soil nitrous oxide (N2O) emission.It is still unclear about the underlying microbial mechanism for N2O emission,particularly in the acidic vegetable soil.By integrating the field experiments with indoor incubations and using real-time quantitative PCR technology,the microbial mechanism for effects of biochar on N2O emissions from an intensive vegetable field was investigated.[Methods] Soil samples were collected from a three-years' field treatment with 22 factorial design at N rates of 0 and 1.25 × 103 kg/hm2 and biochar rates of 0 and 40 t/hm2,namely control (CK),N fertilizer (N),biochar (Bc) and N fertilizer with biochar (N + Bc).The functional genes of ammonia oxidizing archaea (amoA-AOA),ammonia oxidizing bacteria (amoA-AOB),nitrite reductase (nirK,nirS) and nitrous oxide reductase (nosZ),soil pH,inorganic N concentration,in conjunction with soil N2O emissions were measured periodically.[Results] Compared with CK,biochar application significantly increased the concentration of SOC by 27.1％ and TN by 8.2％,significantly decreased the copy numbers ofamoA-AOB and increased the nosZ genes by 11.0％ and 21.2％,and had no significant effects on N2O emissions.Applying nitrogen fertilizer significantly reduced soil pH,increased N2O cumulative emissions,increased the content of inorganic nitrogen and nirK,nirS,nosZ gene copy numbers (P ＜ 05),compared with CK treatment.Compared with N treatment,biochar and nitrogen fertilizer combined application (N + Bc) significantly increased the abundance ofamoA-AOA,amoA-AOB,nirK,nirS and nosZ gene copy numbers by 68.1％,39.3％,21.1％,19.8％ and 48.4％,respectively (P ＜ 0.05),decreased the (nirK + nirS)/nosZ ratio,and reduced N2O emissions by 33.3％.The N2O emission peak appeard at 1-5 d during the indoor incubation,and the emission rate reached N 1.70 × 103 and 1.76 × 103 ng/(kg.h) for the N and N + Bc treatment,respectively.Correlation analysis indicated that N2O emission showed significant positive correlation with the nosZ gene copy numbers (P ＜ 0.05) and the content of NH4+-N (P ＜ 0.01),while significant negative correlation with pH (P ＜ 0.01) during the incubation.[Conclusions] The amendment ofbiochar could decrease N2O emissions from the acidic vegetable soil,which is mainly due to the accelerated N2O reduction via decreasing the ratio of (nirK + nirS)/nosZ.%[目的]生物质炭显著影响土壤氧化亚氮(N2O)排放,但关于其相关微生物机理的研究相对匮乏,尤其是生物质炭对酸性菜地土壤N2O排放的微生物作用机理.本文通过研究氮肥配施生物质炭对酸性菜地土壤N2O排放以及硝化和反硝化过程相关功能基因丰度的影响,探讨酸性菜地土壤N2O排放与功能基因丰度的关系,阐释生物质炭对酸性菜地土壤试验N2O排放的微生物作用机理.[方法]在田间一次性施入生物质炭40 t/hm2,试验连续进行了3年,共9茬蔬菜.设置4个处理:对照(CK)、氮肥(N)、生物质炭(Bc)和氮肥+生物质炭(N+Bc).在施用后第三年,采集土壤样品进行室内培养,应用荧光定量PCR技术检测硝化过程氨氧化古菌(AOA)、氨氧化细菌(AOB)功能基因amoA和反硝化过程亚硝酸还原酶基因(nirK、nirS)以及N2O还原酶基因(nosZ)等相关功能基因丰度,同时监测土壤pH值、无机氮(铵态氮、硝态氮)含量及N2O排放.[结果]与CK相比,生物质炭(Bc)处理的土壤有机碳(SOC)提高了27.1％,总氮(TN)提高了8.2％,amoA-AOB基因丰度显著降低了11.0％,nosZ基因丰度增加了21.2％ (P＜ 0.05),N2O排放没有显著变化(P＞0.05).与CK相比,施用氮肥(N)显著降低土壤pH(P＜0.05),显著增加土壤无机氮含量、nirK、nirS和nosZ功能基因丰度以及土壤N2O累积排放量(P＜0.05).与N处理相比,生物质炭与氮肥联合施用(N+Bc)处理显著增加amoA-AOA、amoA-AOB、nirK、nirS和nosZ基因丰度,增幅分别为68.1％、39.3％、21.1％、19.8％、48.4％ (P＜ 0.05),但(nirK+nirS)/nosZ的比值降低,同时N2O累积排放量显著降低33.3％ (P＜ 0.05).室内培养期间N2O排放峰出现在1～5d,N和N+Bc处理排放速率分别为N 1.70×103和1.76×103 ng/(kg·h).相关分析结果显示,N2O排放速率与氧化亚氮还原酶的标记基因nosZ基因拷贝数(P＜0.05)、NH4+-N含量(P＜0.01)呈显著正相关,与pH呈显著负相关(P＜0.01).[结论]在菜地生态系统中氮肥和生物质炭联合施用可以有效缓解菜地土壤酸化,减少菜地土壤N2O排放,主要归因于反硝化作用nosZ基因丰度增加,(nirK+ nirS)/nosZ比值降低.
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