Mani Rajkumar¹, Sundaramoorthy Soundarya^1,, Ashok Suma Archana¹, Viswanathan Subhadra Varshini¹

Environmental pollution poses a growing threat to worldwide food security and the sustainability of agricultural systems. Encapsulation of bacterial cells presents a promising biotechnological approach to improve the efficacy of biofertilizers and enhance crop productivity. This study evaluated the impact of encapsulated beads containing plant beneficial bacteria (PBB) and biochar (BC) on the growth, photosynthetic pigments, protein content, and relative water content (RWC) of Vigna unguiculata. Out of 24 bacterial isolates, Bacillus velezensis strain TCR11 was selected for its superior seedling growth promotion and its ability to produce key plant beneficial metabolites including indole-3-acetic acid, siderophores, and P-solubilizing compounds. BC was produced from sawdust and bamboo under pyrolysis conditions of 400°C, 550°C, and 700°C. Among all tested BC, the bamboo-derived biochar produced at 550°C (BB2) demonstrated superior performance by significantly promoting plant growth and enhancing the viability of TCR11, making it the optimal matrix for encapsulation with sodium alginate (SA). Pot experiments demonstrated that the encapsulated beads containing TCR11, SA, and BB2 significantly improved V. unguiculata shoot and root length, biomass accumulation, pigment concentration, protein levels, and RWC compared to untreated controls. Moreover, this treatment increased TCR11 colonization in the rhizosphere of V. unguiculata, indicating that BC not only contributed its own benefits but also created a favourable microenvironment that supported the survival and activity of the encapsulated PBB. This likely facilitated the synthesis of growth-promoting metabolites, leading to enhanced plant performance. In conclusion, bamboo-derived BC (BB2) proved to be an effective additive for PBB encapsulation. Combined with PBB, it significantly improved the growth and physiological responses of V. unguiculata, highlighting its potential for sustainable agricultural applications.

Encapsulation, Biochar, Vigna Unguiculata, Bacillus velezensis, Relative Water Content, Rhizosphere