Biological nitrification inhibition is a plant-mediated rhizosphere process where natural nitrification inhibitors can be produced and released by roots to suppress nitrifier activity in soil. Nitrification is one of the critical soil processes in the nitrogen (N) cycle, but unrestricted and rapid nitrification in agricultural systems can result in major losses of N from the plant–soil system (i.e., by NO₃⁻ leaching and gaseous N emissions). In this study, we explored the potential efficacy of biological nitrification inhibitors (linoleic acid [LA] and linolenic acid [LN]) and a proven efficient synthetic (dicyandiamide [DCD]) nitrification inhibitor on N dynamics, nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions in a highly nitrifying soil. ¹⁴C-labelled LA, LN and DCD mineralization was determined in a parallel experiment to explore the fate of inhibitors after application. We found that LA and LN had no effect on soil NH₄⁺ concentrations, but significantly decreased NO₃⁻ concentrations. Soil that received DCD had lower NO₃⁻ and higher NH₄⁺ concentrations than the control (soil without nitrification inhibitors). LA and LN increased the cumulative N₂O and CO₂ emissions when they were applied at high concentrations (635 or 1,270 mg kg⁻¹ dry soil). LA and LN had a much greater mineralization rate than that of DCD: 47–56%, 37–61% and 2.7–5.5%, respectively, after 38 days incubation. We conclude that in contrast to the direct inhibition of nitrification caused by DCD, addition of LA and LN may cause apparent nitrification inhibition by promoting microbial immobilization of soil NH₄⁺ and/or NO₃⁻. Future studies on nitrification inhibitors need to clearly differentiate between the direct and indirect effects that result from addition of these compounds to soil.

中文翻译：

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生物和合成硝化抑制剂在高度硝化土壤中的相对效力和稳定性：亚油酸和亚麻酸明显抑制硝化作用的证据

生物硝化抑制是植物介导的根际过程，在该过程中，根可以产生和释放天然硝化抑制剂，以抑制土壤中的硝化活性。硝化作用是氮 (N) 循环中的关键土壤过程之一，但农业系统中不受限制的快速硝化作用会导致植物 - 土壤系统中的氮大量流失（即通过 NO ₃ ^-浸出和气态氮排放） . 在这项研究中，我们探讨了生物硝化抑制剂（亚油酸 [LA] 和亚麻酸 [LN]）和一种经证实有效的合成（双氰胺 [DCD]）硝化抑制剂对 N 动力学、一氧化二氮 (N ₂ O)的潜在功效和二氧化碳（CO ₂) 高度硝化土壤中的排放。在平行实验中测定¹⁴ C 标记的 LA、LN 和 DCD 矿化，以探索抑制剂在应用后的归宿。我们发现LA 和LN 对土壤NH ₄ ⁺浓度没有影响，但显着降低了NO ₃ ^-浓度。与对照（没有硝化抑制剂的土壤）相比，接受 DCD 的土壤具有更低的 NO ₃ ^-和更高的 NH ₄ ⁺浓度。LA和LN增加累积Ñ ₂ O和CO ₂的排放量，当他们在高浓度施加（635或1270毫克千克^-1干土）。培养 38 天后，LA 和 LN 的矿化率远高于 DCD：分别为 47-56%、37-61% 和 2.7-5.5%。我们得出的结论是，与 DCD 直接抑制硝化作用相反，添加 LA 和 LN 可能通过促进土壤 NH ₄ ⁺和/或 NO ₃ ^{- 的}微生物固定而引起明显的硝化作用抑制。未来对硝化抑制剂的研究需要明确区分将这些化合物添加到土壤中所产生的直接和间接影响。