Abstract Nitrogen (N) applied with fertilizers is not efficiently used in agriculture. In the soil, this N is transformed into different compounds by means of several biological processes. As a result, there is a negative economic and environmental impact due to water contamination, via nitrate (NO3−) leaching, and greenhouse gasses emission, via nitrous oxide (N2O). To reverse this situation, nitrification inhibitors (NI) such as dicyandiamide (DCD), nytrapirin and 3,4-dimethylpyrazole phosphate (DMPP) are widely applied to agricultural soils in order to delay ammonium (NH4+) transformation. A new NI, 3,4-dimethylpyrazole-succinic acid (DMPSA), has been recently developed with the aim of deploying a specific action on ammonium-oxidizing bacteria (AOB). However, previous studies have demonstrated that DMPSA application increases nosZI gene abundance. Thus, non-target populations involved in N-cycle are also affected by its application. For better understanding the effects of DMPSA addition, this NI was applied with ammonium sulfate (AS) fertilizer in a winter wheat crop soil under Humid Mediterranean conditions, in two different soil tillage managements (conventional tillage, CT; and no-tillage, NT). Soil samples were then analyzed by 16S rRNA amplicon sequencing. DMPSA application induced a decrease in bacterial alpha-diversity under the NT management, which showed higher water-filled pore space (WFPS) than the CT management. This suggests that water content played a key role in DMPSA effects. Even at the phyla level, the abundances of several non-target organisms, either involved or not in the N-cycle, were affected by DMPSA application. Within them, the biggest changes were found in Cyanobacteria (+48%) phylum (considered promising bio-agents for sustainable agriculture), which may have also triggered the increase of Bacteroidetes (+20%) and the decrease of certain phytopathogens. This decrease of phytopathogens may have also been helped by the great increase observed after DMPSA application in the genus Vermamoeba vermiformis, a protist known to control/regulate several soil-borne pathogens. Altogether, the results showed that DMPSA may lead to a reduction of the environmental impacts derived not only from the loss of reactive N, but also from the maintenance of a safer microbial community for plant health. However, further studies would be necessary to analyze the persistence and the consequences of all these effects in the long-term.

中文翻译：

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解开 DMPSA 硝化抑制剂对不同耕作制度下土壤细菌群落的影响

摘要 与肥料一起施用的氮 (N) 不能有效地用于农业。在土壤中，这种 N 通过多种生物过程转化为不同的化合物。因此，由于硝酸盐 (NO3-) 浸出造成的水污染和通过氧化亚氮 (N2O) 排放的温室气体，会对经济和环境产生负面影响。为了扭转这种情况，硝化抑制剂 (NI) 如双氰胺 (DCD)、奈曲匹林和 3,4-二甲基吡唑磷酸盐 (DMPP) 被广泛应用于农业土壤，以延迟铵 (NH4+) 的转化。最近开发了一种新的 NI，3,4-二甲基吡唑-琥珀酸 (DMPSA)，目的是对氨氧化细菌 (AOB) 进行特定的操作。然而，先前的研究表明，DMPSA 应用增加了 nosZI 基因丰度。因此，参与 N 循环的非目标人群也受到其应用的影响。为了更好地了解添加 DMPSA 的影响，在潮湿的地中海条件下，在两种不同的土壤耕作管理（常规耕作，CT 和免耕，NT）中，将这种 NI 与硫酸铵 (AS) 肥料一起施用到冬小麦作物土壤中. 然后通过 16S rRNA 扩增子测序分析土壤样品。在 NT 管理下，DMPSA 应用导致细菌 α 多样性降低，这显示出比 CT 管理更高的充水孔隙空间 (WFPS)。这表明水含量在 DMPSA 效应中起关键作用。即使在门级，几种非目标生物的丰度，无论是否参与 N 循环，受到 DMPSA 应用的影响。其中，最大的变化发生在蓝藻（+48%）门（被认为是可持续农业的有希望的生物制剂）中，这可能也引发了拟杆菌（+20%）的增加和某些植物病原体的减少。在蠕虫属（Vermamoeba vermiformis）中应用DMPSA后观察到的显着增加也可能有助于植物病原体的减少，这种原生生物可以控制/调节几种土壤传播的病原体。总而言之，结果表明 DMPSA 可能会导致环境影响减少，这不仅源于活性氮的损失，还源于维护更安全的微生物群落，以促进植物健康。然而，需要进一步的研究来分析所有这些影响的长期持续性和后果。