典型旱作农田土壤氧化亚氮排放的氨氧化微生物相对贡献

Relative Contribution of Ammonia-oxidizing Microorganisms to Nitrous Oxide Emissions in Upland Agricultural Soils

氨氧化过程对氧化亚氮(N2O)排放具有重要贡献。在不同土壤类型和农田管理下,氨氧化微生物类群对N2O排放的相对贡献组成规律还缺乏系统的研究。选取典型农田耕层土壤(潮土、黑土、砖红壤和红壤),以及有机肥改良的砖红壤剖面土壤,采用选择性抑制法(乙炔和辛炔)研究氨氧化细菌(AOB)、氨氧化古菌和全程硝化菌(AOA+comammox)以及异养硝化菌对土壤硝化潜势、净硝化速率及N2O排放的相对贡献。结果表明,在耕层的潮土、黑土、砖红壤和红壤中,硝化潜势随土壤由酸性至碱性显著提高(P<0.05),分别为N 32.5、6.6、4.8和2.3 mg·kg^(-1)·d^(-1),AOB主导四种土壤的硝化潜势(58%~100%)。对耕层的潮土、黑土和砖红壤进一步分析,表明净硝化速率和N2O排放均随pH的增加显著提高(P<0.05),与硝化潜势的规律一致。在潮土和砖红壤中,AOB和AOA+comammox对净硝化速率贡献相当(均在30%~40%),而黑土的净硝化速率由AOB主导(72%)。在潮土、黑土和砖红壤中,N2O排放均由AOB主导(58%~92%)。在有机肥改良的砖红壤剖面土壤中,随土壤由深层至表层,pH、硝化潜势、净硝化速率及N2O排放显著提高(P<0.05)。AOA+comammox主导表层硝化潜势及净硝化速率的提高(分别贡献63%和54%),AOB主导N2O排放的增加(贡献54%)。研究结果为制定与土壤氨氧化特性及土壤性质相匹配的N2O减排措施提供了新的科学依据。

【Objective】Ammonia oxidizers make an important contribution to N2O emissions.However,the composition of their relative contribution to N2O emission in different soils and agricultural management systems has not been systematically studied.【Method】We studied the contributions of AOB,AOA+comammox and heterotrophic nitrifiers to the potential nitrification rate,net nitrification rate and N2O emission in typical upland surface soils(fluvo-aquic soil,black soil,latosol,red soil),and in latosols from soil profile under organic fertilizer amendment.【Result】In the surface fluvo-aquic soil,black soil,latosol and red soil,potential nitrification rate significantly increased with soil pH(P<0.05),and was 32.5,6.6,4.8 and 2.3 mg×kg^(-1)×d^(-1),respectively.AOB dominated the potential nitrification rate in the above surface soils,with contributions ranging 58%-100%.Further analyses of the fluvo-aquic soil,black soil and latosol indicated that net nitrification rate and N2O emission both significantly increased with soil pH(P<0.05),which were consistent with potential nitrification rate.For the net nitrification rate,AOB and AOA+comammox contributed equally(30%-40%)in the fluvo-aquic soil and latosol,while AOB dominated in the black soil(72%).N2O emissions from the fluvo-aquic soil,black soil and latosol were all dominated by AOB(58%-92%).For soils from the organic fertilizer-amended latosol profile,pH,potential nitrification rate,net nitrification rate and N2O emission significantly increased from the subsurface to surface layer(P<0.05).The increase in potential nitrification rate and net nitrification rate was dominated by AOA+comammox(contributing 63%and 54%)and the increase in N2O emission was dominated by AOB(contributing 54%).【Conclusion】This study provides new evidence for developing reduction measures of N2O emissions that match the soil ammonia oxidation characteristics and soil properties.