Abstract :
[en] The application of biosolids is considered a sustainable strategy to improve soil
fertility and crop productivity, but it also poses risks of heavy metals and antibiotics
accumulation, which may impact soil microbial communities and ecological functions.
In order to explore the impacts of biosolids application on soil microbial communities
and reduce the negative effects of heavy metals and antibiotics on soil and plants, we
sampled soil from a 16-year long-term field study, conducted a microcosm experiment
with the addition of heavy metals and antibiotics, and pot experiment with arbuscular
mycorrhizal fungi inoculation. The field study revealed that biosolids application
significantly altered soil bacterial, fungal, and AM fungal communities. While
bacterial communities were predominantly governed by stochastic processes, fungal
and AM fungal assemblies were mainly shaped by deterministic processes. Heavy
metals were identified as major drivers (Hg, Cu, Cd, and Zn for bacteria, Pb and Cr
for fungi, and As and Ni for AM fungi) of the community assembly process. The
results of microcosm showed that heavy metals exerted a dominant selective pressure
on microbial communities and resistance gene profiles during the co-selection of
heavy metals and antibiotics. Furthermore, the core microbiome explained the change
of antibiotic genes and supported microbial community stability. Next, the pot
experiment was conducted to assess the role of AM fungi inoculation in mitigating
environmental risks. We found AM fungal inoculation significantly enhanced plant
biomass, reduced soil and plant heavy metal contents, increased microbial network
complexity, and enriched beneficial heavy metal-resistant microorganisms.
Furthermore, AM fungal inoculation reduced the abundance of mobile genetic
elements, potentially limiting the spread of antibiotic resistance genes. Finally, we
evaluated soil health and multifunctionality by integrating field and pot experiments.
Biosolids application could improve the soil health index and multifunctionality. Soil
bacterial and AM fungal diversity were positively related to multifunctionality. AM
fungal inoculation significantly increased soil multifunctionality by increasing soil
carbon, nitrogen, phosphorus, and sulfur gene abundance. Overall, this study provides
novel insights into the ecological risks and management strategies associated with
biosolids use, offering guidance for sustainable agriculture development.
