Bacterial Richness and Physicochemical Profile of Agro-Soils under Pesticide Application

Abstract

Introduction: Pesticide application modulates agro-soil bacterial richness and physicochemical properties, underpinning ecosystem function and sustainability. Aim: Study investigated bacterial richness and physicochemical parameters of pesticide-polluted soils within the environs of Abraka, Delta State, Nigeria. Place and Duration of Study: Department of Environmental Management and Toxicology, Federal University of Petroleum Resources, Effurun/ March 2024 - June 2024. Methodology: Soil samples were collected from three agricultural farms to ensure representative coverage. Also, a control soil was collected a two hundred meters away from the farms. Bacteria assessment, physicochemical analyses including heavy metals and 16 priority polycyclic aromatic hydrocarbons (PAHs) were determined following standard methods. Results: Results revealed notable alterations in soil properties linked to pesticide use, including increased pH (6.9±0.01 – 7.5±0.00), moisture (9.97±1.31% – 11.35±2.15%), and electrical conductivity (1087±8.90 - 1310±5.30 µS/cm) alongside reductions in sulphate, nitrate, and total organic carbon in some farms. Heavy metals showed spatial variations; lead concentrations increased significantly in farms I (2.80 mg/kg) and II (2.40 mg/kg), while arsenic and mercury remained below detection limits. Chromium, copper, and zinc levels generally declined relative to control sites. Total cultivable heterotrophic bacteria were 42.0 ± 0.00 ×103 CFU/g, 59.2 ± 2.03 ×103 CFU/g, 43.5 ± 1.37 ×103 CFU/g, and 51.3 ± 2.11 ×103 CFU/g in control, Farm I, Farm II, and Farm III, respectively. Bacillus, Chryseobacterium, Klebsiella, Pseudomonas and Staphylococcus were the genera tentatively identified from soils. However, PAHs were below detectable limits (<0.0001 mg/kg) in all farms. Conclusion: This research underscores the need for stringent management of pesticide application, robust monitoring of soil contamination, and development of sustainable remediation strategies to safeguard soil productivity and reduce health risks. Findings contribute to the understanding of contaminant dynamics in tropical agricultural systems and provide a scientific basis for policy interventions addressing agrochemical pollution in Niger-Delta.