Anjaly Yadav, Mahendra Singh, Alok Kumar Pandey, Suresh Kumar, A.K. Singh, Anand Kumar Diwakar, Tripti Mishra, Nitima Singh and Anoop Yadav
Abstract
The present study focused on the standardization of nutrient media for liquid phosphate-solubilizing bacterial (PSB) biofertilizer and its shelf-life evaluation, along with isolation and identification of an efficient PSB strain. Ten bacterial isolates were isolated from rhizospheric soil and screened on Pikovskayaâs agar medium using tricalcium phosphate as an insoluble phosphorus source. Isolate No. 3 exhibited the highest phosphate-solubilization efficiency through pronounced halo zone formation and was molecularly identified as Pseudomonas aeruginosa strain ND-10. The 16S rRNA gene sequence was deposited in the NCBI database with accession number PX699518. Different nutrient broth (NB) compositions were standardized to enhance bacterial viability and storage stability in liquid formulations. The optimized NB formulations (NB-1, NB-2, and NB-3) significantly improved viable cell counts and maintained populations above the recommended threshold of 10x CFU ml-¹ for up to 360 days under ambient storage conditions, whereas the solid carrier formulation showed a rapid decline in viability. Among the formulations, NB-3 exhibited the highest shelf stability, indicating its suitability for long-term storage. Shelf-life performance was further supported by improved survival of PSB on chickpea seed, where liquid formulations recorded significantly higher populations compared to the solid formulation. The study demonstrates that nutrient media standardization is a critical determinant of shelf life and efficacy of liquid PSB biofertilizers. The optimized NB-based liquid formulation of Pseudomonas aeruginosa strain ND-10 offers a promising, stable, and eco-friendly approach for sustainable phosphorus management in agricultural systems.