Abstract Description

Phosphorus (P) is a key macronutrient for plant development, yet its bioavailability in soils is often limited due to fixation in insoluble forms. This study aimed to isolate and evaluate phosphate-solubilising bacteria (PSB) with dual functionality: P-solubilisation and plant growth promotion via phytohormone production. Three bacterial strains Agrobacterium pusense PS2, Cupriavidus cauae PS3, and Bacillus cereus PS4 were isolated and characterised for their ability to solubilise tricalcium phosphate (TCP), produce organic acids, synthesise indole-3-acetic acid (IAA), and promote growth in Swiss chard (Beta vulgaris). Among them, A. pusense PS2 demonstrated superior performance, achieving the highest TCP solubilisation (517.43 ppm), a significant drop in pH (from 6.73 to 5.55), organic acid production (6.06 mM), and IAA synthesis (75.3 mg/L). Correspondingly, it promoted substantial increases in root and shoot length in inoculated seedlings. These findings highlight A. pusense PS2 as a promising biofertiliser candidate for improving P availability and crop growth, especially in P-deficient or chemically burdened soils. It’s application could contribute to reducing reliance on synthetic fertilisers, promoting soil health, and supporting more sustainable, biologically driven agricultural practices in South Africa and similar contexts.