Optimizing Nitrogen Enrichment in Industrial Compost Production Through Azotobacter spp. Inoculation: A Case Study in Sri Lanka

Waste management is a crucial global challenge due to the negative impacts waste can have on the environment and human health. This research study focused on isolating and evaluating Azotobacter spp., a nitrogen-fixing bacterium, and its impact on chili plants grown in compost made with biodegradable waste. Azotobacter spp. were isolated using Ashby's nitrogen-free media and characterized through morphological and biochemical tests, confirming their identity as gram-negative bacteria. The effects of different treatments on plant growth parameters, including plant height, number of leaves, girth of stem, number of branches, and number of flowers, were examined over 70 days. The results revealed that Azotobacter spp. significantly affected plant growth, with treatment T1 (5% microbial consortia mixed compost) demonstrating the highest plant height and number of leaves. When combined with topsoil, the microbial consortia mixed compost enhanced plant growth parameters, potentially due to the increased fungal population facilitated by Azotobacter spp. However, higher concentrations of microbial consortia (as in T3) appeared to disrupt nutrient availability and hinder plant growth. Moreover, the study showed a positive correlation between the potting mixture’s Azotobacter spp.—population and nitrogen content. The highest nitrogen content was recorded in T3, suggesting a higher population of Azotobacter spp. and led to increased biological nitrogen fixation. In conclusion, this research emphasizes the positive impact of Azotobacter spp. on chili plant growth. It highlights the potential benefits of microbial consortia mixed compost when used in combination with topsoil. The findings also underline the significance of maintaining a balanced microbial population for optimal plant growth. Furthermore, the study underscores the importance of composting for sustainable biodegradable waste management in Sri Lanka, with opportunities for enhancing compost quality by adding specific ingredients, such as phosphate, urea, and muriate of potash.