Plants can directly affect nitrogen (N) transformation processes at the micro-ecological scale when soil comes into contact with roots. Due to the methodological limitations in measuring direct N2 losses in plant-soil systems, however, the effect of rhizosphere processes on N2O production and reduction to N2 has rarely been quantified. For the first time, we developed a robotic continuous flow plant-soil incubation system (using a He+O2 + CO2) combined with N2O 15N site preference approach to examine the effect of plant root activity (barley – Hordeum vulgare L.) on: i) soil-borne N2O and N2 emissions, ii) the specific contribution of different pathways to N2O fluxes in moist soils (85% water holding capacity) receiving different inorganic N forms. Our results showed that when a nitrate-based N fertiliser was applied, the presence of plants tripled both N2O and N2 losses during the growth period but did not alter the N2O/(N2O + N2) product ratio. The 15N site preference data indicated that bacterial denitrification was the dominant source contributing to the observed N2O fluxes in both nitrate and ammonium treated soils, whereas the presence of barley increased the contribution of fungal N2O in the nitrate treated soils. During the post-harvest period, N2O and N2 emissions significantly increased in the ammonium-fertilised treatment, being more pronounced in the soil with a senescing root system. Overall, our study showed a significant interaction between rhizosphere processes and N forms on the magnitude, patterns, and sources of soil borne N2O and N2 emissions in moist agricultural soils.

中文翻译：

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由于细菌和真菌反硝化作用增强，富含硝酸盐的大麦土壤的根际过程使 N2O 和 N2 损失增加了两倍

当土壤与根部接触时，植物可以直接影响微生态尺度上的氮 (N) 转化过程。然而，由于测量植物-土壤系统中直接 N2 损失的方法学限制，根际过程对 N2O 产生和还原为 N2 的影响很少被量化。我们首次开发了机器人连续流动植物-土壤孵化系统（使用 He+O2 + CO2）结合 N2O 15N 场地偏好方法来检查植物根系活动（大麦 – 大麦）对以下方面的影响： i) 土壤中的 N2O 和 N2 排放，ii) 不同途径对接收不同无机 N 形式的潮湿土壤（85% 持水量）中 N2O 通量的具体贡献。我们的结果表明，当施用以硝酸盐为基础的氮肥时，在生长期间，植物的存在使 N2O 和 N2 损失增加了两倍，但并未改变 N2O/(N2O + N2) 产品比率。15N 选址数据表明细菌反硝化作用是硝酸盐和铵处理土壤中观察到的 N2O 通量的主要来源，而大麦的存在增加了硝酸盐处理土壤中真菌 N2O 的贡献。在收获后阶段，铵肥处理中 N2O 和 N2 的排放量显着增加，在根系衰老的土壤中更为明显。总体而言，我们的研究表明，根际过程和 N 形态之间在潮湿农业土壤中土壤中 N2O 和 N2 排放量的大小、模式和来源方面存在显着的相互作用。