Impact of pesticide residues on arable soil microbiomes

Pesticides are widely applied in agriculture to combat disease, pests, and weeds, leading to widespread and chronic contamination of agricultural soils with pesticide residues. However, it is still poorly understood whether continuous exposure to pesticide residues affects the soil microbiome. Here we assessed bacterial and fungal communities and several genes related to nitrogen cycling in soils of 60 wheat fields across Switzerland. We then examined whether pesticide residues are linked to the structure and functioning of the soil microbiome. Pesticides had a significant effect on various traits of the soil microbiome. The diversity of bacteria was negatively linked to the concentration of various pesticide residues, while fungal diversity and abundance were positively affected. Pesticide residues significantly explained the abundance of 1.3% of all bacterial (111 taxa in total) taxa and 8.9% of all fungal taxa (129 taxa in total). Most of these taxa were positively associated to the occurrence of pesticides, possibly because such taxa could use pesticides as food and energy source, while few taxa declined in response to increasing pesticide concentrations. Moreover, specific pesticide residues enriched one taxonomic group (Chloroflexi) and a functional guild (saprotrophic fungi). Nitrogen cycling genes were linked to pesticide residues, with several pesticide residues having a negative influence on the abundance of the gene nifH, involved in biological nitrogen fixation. Interestingly, the effects of pesticides on microbial traits were stronger than effects of cropping system and management practices including tillage, fertilisation and crop rotation. Our results suggest that chronic exposure to pesticide residues is an important factor shaping the composition and functioning of the arable soil microbiome. This indicates that the use of pesticides has long-term effects on agricultural soils, which may interfere with the development of sustainable farming systems.

农药在农业生产中被广泛施用，用于防治病害、虫害与杂草，由此造成农业土壤被农药残留大范围且持续性污染。然而，目前学界对持续暴露于农药残留是否会影响土壤微生物组（soil microbiome）仍缺乏充分认知。本研究针对瑞士境内60块麦田的土壤开展分析，对其中的细菌与真菌群落，以及若干与氮循环相关的基因进行了评估。随后，我们探究了农药残留与土壤微生物组的结构及功能是否存在关联。研究结果显示，农药对土壤微生物组的多项特征具有显著影响：细菌多样性与多种农药残留浓度呈负相关，而真菌多样性与丰度则受到正向影响。农药残留可显著解释1.3%的总细菌类群（共计111个分类单元）以及8.9%的总真菌类群（共计129个分类单元）的丰度变化。其中绝大多数类群的丰度与农药的检出呈正相关，推测此类类群能够以农药作为食物与能量来源；仅有少数类群的丰度随农药浓度升高而降低。此外，特定农药残留会富集一类分类群——绿弯菌门（Chloroflexi），以及一类功能类群——腐生真菌（saprotrophic fungi）。氮循环相关基因与农药残留存在关联，多种农药残留对参与生物固氮的nifH基因的丰度具有负向影响。值得注意的是，农药对微生物特征的影响强度超过了耕作制度与管理措施（包括耕作、施肥与作物轮作）所带来的影响。本研究结果表明，长期暴露于农药残留是塑造耕地土壤微生物组组成与功能的重要因素。这意味着农药的使用会对农业土壤产生长期影响，可能会干扰可持续农业系统的构建与发展。