Boron-induced microbial filtering delays early rhizosphere establishment in agricultural soil

Excessive application of boron-based fertilizers in agriculture has led to increased boron accumulation in soil, adversely affecting microbial communities and plant species, ultimately contributing to boron-induced desertification. This study presents the first metagenome-based analysis of boron-contaminated agricultural soil in Northern West Bengal, India, providing a comprehensive profile of the soil microbiome under boron stress. Boron-amended and unamended agricultural soil samples were analyzed using metagenomics sequencing approach over 365 days under natural environmental conditions. The results revealed a significant decline in bacterial diversity in boron-amended soil, with Firmicutes emerging as the dominant phylum. Notably, all boron-tolerant bacterial strains belonged to Firmicutes, suggesting that high boron levels impose selective pressure favouring Gram-positive bacteria. The enrichment of metal-resistant and oligotrophic bacterial taxa in boron-amended soil underscores microbial adaptation to boron stress. In addition to microbial community dynamics, we investigated plant succession in boron-enriched soil, offering novel insights into the interplay between above- and below-ground ecosystems. Our findings highlight two key adaptive traits, high boron tolerance and oligotrophic survival strategies, that enable bacterial communities to persist in boron-rich environments. These results enhance our understanding of microbial resilience in chemically stressed soils and have implications for soil health and sustainable agriculture.