Synergistic effects of nitrogen-fixing bacteria and varying coir dust ratios on plant growth: A green approach

Nitrogen-fixing bacteria (NFB) play a vital role in sustainable agriculture. They enhance soil nitrogen availability, reduce reliance on synthetic fertilizers, and promote plant growth. This study aimed to isolate and characterize NFB strains from compost soil and evaluate their potential to improve nitrogen uptake and plant growth. Genotypic identification confirmed that the isolated strains belonged to six species of the Bacillus genus and one Microbacterium aquimaris species. All isolated Bacillus spp. strains and Microbacterium aquimaris tested positive for nitrogen-fixing activity and ammonia production tests. The highest ammonia (1.6 ± 0.5 mg/L) and nitrate (1.08 ± 0.04 mg/L) production were recorded in Ashby broth medium inoculated with the Bacillus cereus strain after 7 days of incubation period. The potting media consisted of a ratio 1 inoculated with the Bacillus cereus strain CCM 2010, which exhibited the highest growth parameters, including maximum root length (11.3 ± 1.1 cm), shoot length (17.5 ± 0.5 cm), wet weight (0.6898 ± 0.1 g), and dry weight (0.1015 ± 0.01 g). These findings suggest that integrating NFB with varying ratios of coir dust in potting media significantly enhances plant growth, suggesting a viable and sustainable approach to improving agricultural productivity.