Molecular Insights into Soil Amendments Regulating Selenium and Cadmium Bioavailability in a Soil-Rapeseed System:...

Area of Science:

• Environmental Science
• Soil Science
• Biogeochemistry

Background:

• Selenium (Se) and cadmium (Cd) co-occur naturally in soils, posing risks to ecosystems and human health.
• Soil amendments are used to manage metal bioavailability, but mechanisms for Se/Cd regulation remain unclear.
• Understanding amendment effects on Se/Cd bioavailability is crucial for agricultural sustainability.

Purpose of the Study:

• To investigate how calcium superphosphate (P), biochar (BC), and organic manure (OM) affect Se and Cd bioavailability in a seleniferous soil-rapeseed system.
• To elucidate the underlying mechanisms, including microbial community shifts and metabolite changes.
• To provide insights for selecting appropriate amendments based on soil Se/Cd bioavailability.

Main Methods:

• Application of three soil amendments: calcium superphosphate (P), biochar (BC), and organic manure (OM).
• Analysis of Se and Cd accumulation in rapeseed and soil.
• Characterization of soil organic matter components and microbial community structure (16S rRNA sequencing).
• Metabolomic analysis to identify biochemical pathway alterations.

Main Results:

• Calcium superphosphate (P) reduced Se accumulation; biochar (BC) enhanced Se but reduced Cd; organic manure (OM) reduced both Se and Cd.
• All amendments altered soil organic matter composition, decreasing microbial-derived humic-like components (C1).
• OM and BC significantly enriched Actinobacteriota, with OM particularly promoting *Promicromonospora*-mediated Se/Cd immobilization.
• Metabolomics indicated amendment-specific effects on lipid, amino acid, and general microbial metabolism, influencing Se transformation and immobilization.

Conclusions:

• Soil amendments regulate Se/Cd bioavailability through complex interactions involving dissolved organic matter (DOM), microbial communities, and metabolites.
• Organic manure and biochar show potential for immobilizing both Se and Cd by stimulating specific microbial groups and metabolic pathways.
• Amendment choice should be tailored to the specific Se/Cd bioavailability characteristics of the target soil.