Microbial-driven soil remediation: Comparative analysis of seven microbial agents on alachlor degradation rates and tobacco phytotoxicity recovery

Abstract

The presence of alachlor residue in soil has been demonstrated to exert a deleterious effect on the subsequent cultivation of crops, resulting in substantial impairment to agricultural output. Application of alachlor at twice the recommended dose notably inhibited tobacco growth, reducing plant height to 39.68 % of the control, stem girth to 40.06 %, maximum leaf length to 45.52 %, and maximum leaf width to 42.05 %. A total of seven functional microbial agents were screened for their potential to alleviate tobacco phytotoxicity. Results demonstrated that two microbial agents, Purpureocillium lilacinum (PL) and Pseudomonas fluorescens (PF), significantly alleviated toxicity, enhancing plant height, stem girth, and leaf expansion (P < 0.001 or P < 0.01). This study also developed and validated an efficient method for detecting alachlor in soil, demonstrating excellent linearity (R² > 0.99) with recoveries ranging from 88.98 % to 93.60 %, a limit of detection (LOD) of 0.0005 mg/kg, and a limit of quantification (LOQ) of 0.02 mg/kg. The degradation efficiency of alachlor varied among microbial agents, with PL and PF exhibiting the highest degradation rates of 93.50 ± 0.69 % and 90.80 ± 1.02 % at 70 days post-application. Microbial diversity analysis showed that PL and PF treatments increased the abundance of Actinobacteria and specific microbial genera, which facilitated alachlor degradation and improved soil ecological conditions. These findings suggest that PL and PF hold significant potential to accelerate alachlor degradation, alleviate alachlor toxicity, and enhance soil health, offering valuable insights for farmland pollution remediation.