Evaluation of phosphorus solubilizing bacteria for enhanced phosphorus uptake in acidic soils

Abstract:

Phosphorus fixation in acidic soils locks away up to 85% of applied fertiliser within days of application, leaving crops chronically P-deficient. This research evaluated five phosphorus solubilizing bacteria (PSB) isolates for their ability to mobilise fixed P and improve uptake in rice grown on acidic red soils (pH 4.7) at Lembucherra, Tripura, during Kharif 2022 and 2023. Isolates were characterised for solubilisation efficiency on Pikovskaya’s agar before field inoculation. The most effective strain, Pseudomonas fluorescens TPA-7, raised available P in the rhizosphere by 63.4% over the uninoculated control and increased grain P uptake to 17.4 kg ha^-1 (vs. 8.3 kg ha^-1 in the control). Grain yield under TPA-7 + 75% recommended P was statistically equal to full P without inoculation, implying a 25% saving on phosphatic fertiliser. Organic acid profiling showed that gluconic and oxalic acids were the dominant solubilising agents. These results support integrating PSB inoculants into fertiliser schedules for acid-soil rice production in north-eastern India.