Bacterial Heterogeneity and Density of Glufosinate Ammonium Contaminated Soil: A Microcosm Study

Abstract

Introduction: Indiscriminate use of herbicides in agriculture poses significant threats to soil health, particularly by affecting the diversity and abundance of soil microorganisms Aim: This study investigated the effects of glufosinate ammonium on soil microbial communities and physicochemical properties. Study Design: A microcosm experiment was carried out in the laboratory to ascertain the short term effects of glufosinate ammonium application on soil microorganisms. Place and Duration of Study: Department of Environmental Management &Toxicology, Federal University of Petroleum Resources, Effurun/ June-August, 2024. Methodology: One kilogram of soil was contaminated with the herbicide (20mL and 60mL (v/w)) in triplicates. A control was set-up without the herbicide.  Soil samples were collected from herbicide-treated and untreated microcosms and analyzed for physicochemicals and heterotrophic biota before and two weeks after contamination. Results: Baseline analysis revealed pH, organic carbon content, lead and cadmium values were 6.40, 1.46%, 6.42 mg/kg and 0.1 mg/kg, respectively. Total heterotrophic bacterial and fungal counts were 2 × 104 CFU/g and 1.65 × 104 CFU/g. Furthermore, values for pH, organic carbon, lead, cadmium were 7.40, 1.30%, 6.9mg/kg and 0.16mg/kg (control), 7.60, 1.64%, 6.22mg/kg, 0.10mg/kg (20mL), 7.7, 1.68%, 8.10mg/kg and 0.18mg/kg (60mL), respectively. Total heterotrophic bacterial counts were 5.0 × 104 CFU/g (control), 3.30 × 104 CFU/g (20mL) and 3.00 × 104 CFU/g (60mL) while total heterotrophic fungal counts were 3.25 × 104 CFU/g (control), 3.00 × 104 CFU/g (20mL) and 2.50 × 104 CFU/g (60mL) after contamination. Species of Bacillus, Enterobacter, Paenibacillus, Corynebacterium, Enterococcus, Klebsiella, Proteus, Pseudomonas and Staphylococcus were identified in this study. Conclusion: The results revealed that herbicides significantly altered the microbial population, with heterotrophic fungi showing resilience. This study contributes to understanding the complex interactions between herbicides, soil microorganisms, and physicochemical properties, providing a foundation for sustainable agricultural practices in herbicide-treated environments.