Pesticides Application Influence Soil Fertility and Bacterial Diversity in Pepper Farms in Ogume, Delta State

Abstract

Pesticides not only eliminate target pests but also affect non-target soil organisms that play critical roles in maintaining soil fertility and ecological balance. This study assessed the impact of pesticide application on soil fertility and microbial diversity in pepper farms in Ogume, Delta State, Nigeria. The research compared two actively managed, pesticide-treated farms (Agrochemical Farm 1 (AFS 1) and Agrochemical Farm 2 (AFS 2)) against a control site (C). Standard methods analyzed soil physicochemical properties, and culturable microbial communities were characterized using selective media and Analytical Profile Index (API). Data were analyzed via one-way ANOVA and Tukey’s HSD test. Pesticide application significantly altered soil properties: AFS 1 exhibited higher electrical conductivity (351 µS/cm against Control: 155 µS/cm; p<0.001), elevated nutrient levels (e.g., Nitrate: 1.84 mg/kg compared with control; 0.75 mg/kg), and increased cation exchange capacity (1.76 cmol/kg in contrast with 0.91 cmol/kg in control). Microbial counts showed a significant reduction in total heterotrophic bacteria in AFS 1 (86.8 x 10⁵ CFU/g) compared to the control (128.0 x 10⁵ CFU/g), while actinomycetes were enriched (64.3 x 10⁴ CFU/g against 54.5 x 10⁴ CFU/g). Cultivation revealed a shift in community structure, with the isolation of potential human pathogens such as Escherichia coli, Klebsiella pneumoniae, Enterobacter aerogenes, Staphylococcus aureus, Salmonella typhimurium, and Shigella spp. from pesticide-treated soils. Study showed that pesticides usage in these farms degrades soil health by increasing salinity, altering nutrient profiles, suppressing beneficial heterotrophic bacteria, and enriching for tolerant and potentially pathogenic taxa. This provides critical site-specific evidence for the study area, highlighting significant ecological and public health risks. Therefore, urgent adoption of integrated pest management and stricter enforcement of pesticide regulations to ensure agricultural sustainability is recommended.