Unveiling the microbial dynamics in vermicomposting with coir pith as earthworm substrate

This study explored the impact of incorporating coir pith, a byproduct of the coconut industry, into the vermicomposting substrate of Eudrilus eugeniae earthworms. The groups were compared based on their diets: cow manure only or cow manure mixed with varying amounts of coir pith. The aim was to assess the effects of coir pith on earthworm growth, mortality, and the microbial community involved in vermicomposting. The results indicated that earthworms fed with higher proportions of coir pith (70% w/w) experienced reduced growth (0.81 g/worm) and increased mortality (24.67%) after 5 weeks of vermicomposting. These effects were attributed to the high level of total phenolic content in the system.Coir pith required specific bacteria for digestion and detoxification, and excessive intake disrupted the earthworms' digestion, thus, hindering nutrient absorption. The study also examined the microbial composition of the vermicast samples and identified variations based on the diet. Bacterial families involved in lignocellulose degradation, such as Bacteriodota, Azosprillum, Chitinophagaceae, Marinomonas, and Pantaea, exhibited decreased abundance in treatments fed with coir pith. Conversely, potentially harmful bacteria like Aeromonas increased with higher coir pith content. This pioneering investigation sheds more light on the feasibility of coir pith utilization in vermicomposting and emphasizes the importance of optimizing earthworm diets to enhance microbial ecology and improve vermicompost quality.