Occurrence and 15N-quantification of simultaneous nitrification and denitrification in N-fertilised soils incubated under oxygen-limiting conditions
Occurrence and 15N-quantification of simultaneous nitrification and denitrification in N-fertilised soils incubated under oxygen-limiting conditions
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DOI：
10.1016/j.soilbio.2020.107757
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发表时间：
2020-04-01
影响因子：
9.7
通讯作者：
Cardenas, Laura M.
中科院分区：
文献类型：
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作者：
Castellano-Hinojosa, Antonio;Charteris, Alice F.;Cardenas, Laura M.
已知硝化和反硝化在土壤中共同发生，但施肥历史对N2O通量的影响以及N2O的相对来源分配尚未得到深入研究。因此，在这项研究中，我们将高科技的N-15稳定同位素示踪技术与定量PCR （qPCR）相结合，探讨了在3年前反复处理硫酸铵[(NH4)(2)SO4]或硝酸钾（KNO3）的砂质壤土中，硝化和反硝化对N2O产量的相对贡献。用（(NH4)-N-15）(2)SO4和(KNO3)-N-15分别对两种土壤(历史处理的（NH4）（2)SO4和(KNO3)-N-15）进行处理，并在80%充满水的孔隙空间中培养30天。测定了土壤N2O排放量、NH4+和NO3-浓度及其对应的n -15浓度。还计算了N添加对N转化速率的影响。利用细菌和古菌中amoA基因的qPCR估计了硝化菌的总丰度，以nirK、nirS、norB和nosZI基因为分子靶点估计了反硝化菌的总丰度。在历史（NH4）(2) so4处理的土壤中，培养期间排放的N2O中49.0 ~ 58.0%来自硝化作用，42.0 ~ 51.0%来自反硝化作用。N2O的产生伴随着土壤NH4+浓度的降低和土壤NO3-浓度的增加。此外，细菌和古菌amoA基因的丰度在孵育过程中增加。相反，在历史上施用过KNO3的土壤中，N-15同位素分析表明，反硝化作用贡献了84.0-99.0%的N2O总量。土壤NO3-浓度的降低与N2O的N-15富集和nirK、nirS、norB和nosZI基因丰度的增加相一致。结果还表明，在kno3处理的土壤中，N-15(2)的富集值显著更高，这与nosZl基因的高丰度是一致的。N转化速率的计算表明，在历史（NH4）(2) so4处理土壤中，自养硝化和反硝化作用是N2O产生的主要原因，而反硝化作用是KNO3处理土壤中最重要的N2O来源。我们得出结论，氮肥历史，而不仅仅是土壤氧有效性，影响硝化和反硝化对土壤N2O排放的相对贡献。事实上，在这里我们已经表明，即使在保持高含水量的土壤中，硝化作用也可能是一个重要的N2O来源过程。
Nitrification and denitrification are known to co-occur in soils, but the effect of fertilisation history on N2O fluxes and the relative source partitioning of the N2O has not been thoroughly investigated. In this study, we therefore combined a high-tech N-15 stable isotope tracing technique with quantitative PCR (qPCR) to explore the relative contributions of nitrification and denitrification to N2O production by a sandy-loam Eutric Cambisol soil treated repeatedly with ammonium sulfate [(NH4)(2)SO4] or potassium nitrate (KNO3) for 3 years prior. Both soils (historically (NH4)(2)SO4 and historically KNO3 treated) were amended separately with ((NH4)-N-15)(2)SO4 and (KNO3)-N-15 and incubated at 80% water filled pore space for 30 days. Soil N2O emissions, NH4+ and NO3- concentrations and their corresponding N-15-enrichments were determined. The effect of N addition on N transformation rates was also calculated. The total abundance of nitrifiers was estimated by qPCR of the amoA gene from bacteria and archaea, and that of denitrifiers by using the nirK, nirS, norB and nosZI genes as molecular targets. In the historically (NH4)(2)SO4-treated soil, 49.0-58.0% of the N2O emitted originated from nitrification and 42.0-51.0% from denitrification during incubation. The production of N2O was accompanied by a decrease in soil NH4+ concentrations and a parallel increase in the concentration of soil NO3-. In addition, the abundance of the bacterial and archaeal amoA gene increased during the incubation. Conversely, in the soil historically treated with KNO3, the N-15 isotopic analyses showed that denitrification contributed 84.0-99.0% of the total N2O produced. Decreases in soil NO3- concentrations paralleled the increase in N-15 enrichment of N2O and the abundance of the nirK, nirS, norB and nosZI genes. The results also showed that values of N-15(2) enrichment were significantly higher in the KNO3-treated soil, which is in line with the higher abundance of the nosZl gene. Calculation of the N transformation rates indicated that autotrophic nitrification and denitrification were responsible for N2O production in the historically (NH4)(2)SO4-treated soil and that denitrification was the most important N2O source in the soil treated with KNO3. We conclude that N-fertilisation history, and not simply soil oxygen availability, affect the relative contributions of nitrification and denitrification to soil N2O emissions. Indeed, here we have shown that nitrification can be an important N2O source process even in soils maintained at high moisture contents.