Pre- and Post-Emergence Herbicide-Induced Shifts in Soil Microbial Communities: Effects on Population Dynamics, Mechanistic Insights, and Ecosystem Function

Herbicides are commonly used in agricultural practices to control weeds and significantly impact soil microbial communities, which are essential for maintaining soil health and ecosystem functions. Herbicides are the most widely used class of pesticides globally, yet they also have detrimental effects, while the rising cost of agricultural labor has recently driven a significant increase in herbicide use. According to the World Health Organization (WHO), three million cases of pesticide poisoning were reported. Certain herbicides may inhibit or promote specific microbial taxa, thereby altering community composition and functionality. These alterations can disrupt crucial soil processes, including nutrient cycling, organic matter degradation, and plant–microbe interactions, potentially diminishing soil fertility and increasing vulnerability to pathogen invasions. Moreover, the duration and intensity of microbial responses are influenced by the persistence and bioavailability of herbicides in the soil, which can differ based on soil characteristics, climatic factors, and the patterns of herbicide application. This review emphasizes recent progress in understanding the molecular mechanisms that drive microbial responses to herbicides, including modifications in gene expression, enzyme activity, and adaptive stress responses. Pre- and post-emergence herbicides alter soil microbial communities, reducing beneficial microbes, disrupting plant–microbe interactions, and affecting nutrient cycling and soil fertility. However, the effects vary with herbicide type, soil properties, and environmental conditions. Thus, promoting alternative weed management and monitoring microbial responses can help maintain soil biodiversity and support sustainable agriculture. Moreover, by investigating both the immediate and long-term effects on microbial communities and ecosystem functioning, this paper aims to provide a comprehensive understanding of the impact of herbicide use on soil ecology and sustainability. This review is a concise draft on the mechanistic basis of herbicide effects on microbial population dynamics, focusing on how various herbicide classes affect microbial diversity, community structure, and metabolic activities.