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Co-application of organic fertilizer and biochar ameliorates the triple composite pollution of microplastics, antibiotic resistance genes, and heavy metals in soil
Summary
Agricultural soils are increasingly polluted by a troubling combination of heavy metals, microplastics, and antibiotic-resistant bacteria — and this five-year field study found that combining biochar with organic fertilizer significantly reduces all three types of contamination at once. The treatment worked by reshaping soil microbial communities in ways that suppressed antibiotic-resistant organisms while promoting microbes that break down plastics and immobilize metals. This approach offers a practical, field-tested strategy for cleaning up complex pollution in intensively farmed soils.
Intensive facility agriculture is increasingly threatened by the co-occurrence of heavy metals (HMs), micro-/nano plastics (MNPs), and antibiotic resistance genes (ARGs), yet effective strategies for mitigating ternary composite pollution remain limited. Here, a five-year field trail was conducted to evaluate the imparts of different fertilization regimes on the occurrence, interaction, and mitigation of composite pollution in facility agricultural soils, with a particular attention on the co-application of biochar and organic fertilizer. The results showed that conventional fertilization exacerbated the accumulation and synergistic risks of HMs, MNPs, and ARGs, whereas its co-applied with biochar significantly reduced individual pollutant loads and lowered the comprehensive ternary pollution index by 28.0-62.2 %. Variance partitioning and structural equation modeling revealed that microbial community structure played a dominant role in regulating composite pollution, exceeding the contribution of soil physicochemical properties. The biochar-organic fertilizer amendment reshaped microbial community assembly by narrowing ecological niche breadth, enhancing community stability, which primarily drove a targeted enrichment of functional taxa (e.g. Nitrospira, Sphingopyxis, Hydrogenophaga, and Steroidobacter) involved in microplastic degradation and heavy metal immobilization, concurrently suppressing ARGs host populations. Metagenomic analyses indicated a dual-level regulation of microbial carbon metabolism. The treatment enhanced fermentation-driven, energy-efficient carbon conversion pathways in functional microbes responsible for plastic degradation and metal immobilization, while concurrently inhibiting carbon fixation-dependent metabolic functions in ARG-associated hosts, thereby reducing their ecological competitiveness. Overall, this study highlights carbon resource-driven microbial metabolic differentiation as a central mechanism for the synergistic mitigation of complex soil pollution and provides a practical fertilization strategy for sustainable pollution control in protected agricultural systems.
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