Novel Strategy for Alleviating Imazethapyr Phytotoxicity in Subsequent Wheat Seedlings: Insights into Multifunctional Mechanisms of Phosphorus-Doped Biochar

Abstract Imazethapyr is a widely used persistent herbicide that causes severe phytotoxicity to rotational crops and threatens soil ecosystem health and agricultural sustainability. Although pristine biochar has been explored for pesticide-contaminated soil remediation, its low adsorption capacity and limited efficiency restrict practical application. Phosphorus (P)-doped biochar exhibits enhanced sorption ability toward organic pollutants, yet its effects and mechanisms in alleviating imazethapyr-induced soil toxicity remain largely unknown. This study systematically compared the remediation performance of P-doped corn straw biochar (PBC-500) and pristine biochar (BC-500) in imazethapyr-contaminated soil using a multimethod approach including herbicide residue analysis, wheat seedling growth assessment, soil microbial community profiling, and wheat root metabolomics. Results showed that by day 4 of the incubation, PBC-500 reduced imazethapyr concentrations in soil and pore water by 82.3%, significantly higher than the 46.1% reduction achieved by BC-500. PBC-500 effectively mitigated herbicide-induced phytotoxicity, improved wheat growth and chlorophyll content, and suppressed ROS (reactive oxygen species) accumulation. It was also associated with stabilization of the soil microbial community structure and changes of root metabolic pathways. Metabolomic analysis further showed that PBC-500 alleviated specific imazethapyr-induced metabolic perturbations at the pathway level based on candidate metabolites (screened without FDR correction), although substantial differences between IMTPBC and the control remained, indicating that the observed metabolic changes partly reflect the biochar’s own effects. However, because the experimental design lacked biochar-only controls, these microbial and metabolic effects should be interpreted as changes co-occurring with PBC-500 amendment, and their specific driver cannot be definitively isolated under the current design. Overall, P-doped biochar efficiently reduces imazethapyr bioavailability and alleviates phytotoxicity, providing a promising eco-friendly material for remediation of imazethapyr-contaminated agricultural soils, with potential for integration into rotational cropping systems to protect subsequent sensitive crops.