This study investigates the role of microbial dynamics during the fermentation of buffalo dung and urine-fermented plant growth-promoting formulation, a natural biofertilizer, and its impact on plant growth and soil health. This formulation was prepared using Surti buffalo dung, urine, jaggery, gram flour, and soil and fermented for up to 14 days. Metagenomic analysis revealed microbial succession from a diverse initial community to a Bacillus-dominated population, especially the Lactic Acid Bacteria, after 8 days of fermentation. The changes were accompanied by increases in the plant growth-promoting genes related to nutrient acquisition, phytohormone production, and stress resistance. The pot experiment revealed a significant increase in mung bean growth, with the maximum effect obtained from the eighth-day fermented formulation. The experiment showed considerable improvement in the physicochemical properties of soil, including increased organic carbon and nutrient availability. These findings underscore the ecological importance of microbial input preparation in enhancing soil fertility and plant growth sustainably. Future research should delve deeper into the specific mechanisms these microbes facilitate nutrient cycling and resilience in various agroclimatic conditions.