IMPACT OF PESTICIDES USE ON SOIL MICROBIAL COMMUNITIES

Abstract

The increasing global use of agrochemicals in ensuring food security has posed severe ecotoxicological risks to agricultural soil ecosystems. Soil microbes are foundation of soil fertility, playing critical roles in vital biogeochemical processes like carbon sequestration, nitrogen fixation, phosphorus solubilization, and sulfur cycling. However, continuous use and accumulation of diverse pesticide active ingredients have posed severe risks on microbial diversity assembly and stability. Classical pesticide risk assessments have traditionally been based on single active ingredient-based assessments under extremely controlled laboratory conditions. However, modern-day agricultural ecosystems are characterized by high pesticide diversity where co-occurrence of multiple active ingredients like herbicides, insecticides and fungicides poses complex multi-stressor conditions. These chemical cocktails have potential to act synergistically thus increasing the overall ecological stress while reshaping fundamental microbial network topologies. Advances in high-throughput sequencing technologies and metagenomic studies clearly demonstrated that high pesticide diversity leads to reduced stochastic microbial assembly, favoring growth of deterministic specialists and opportunistic microbes with ability to degrade xenobiotics. Consequently, evolutionary forces like genome streamlining led to enhanced expressions of specific functional genes which are associated with rapid nutrient cycling, thus paradoxically accelerating depletion of critical soil resources. This comprehensive review critically evaluates distinct impacts of herbicides, insecticides, and fungicides on soil microbiomes, emphasizing disruption of enzymatic activities such as those of dehydrogenase, urease, and nitrogenase. Furthermore, it explores utility of molecular biomarkers and proposes agronomic interventions specifically nitrogen fertilization and conservation tillage to mitigate Eco toxicological risks. By integrating these molecular insights with agronomic management, this review provides framework for preserving long-term soil health and redefining regulatory pesticide risk assessments