Pseudomonas striata for Improving Phosphorus Availability in Soil under Pearl Millet Cultivation

Abstract

Phosphate-dissolving microorganisms can be vital in promoting the bioavailability of phosphorus in soil characterized by high total P. Their additional property of phyto-hormone production can be advantageous for improving crop growth. Pseudomonas striata evaluated for phytate mineralization and solubilization of tricalcium, rock, ferric, and aluminum phosphate showed high potential as phosphobacteria. Chromatographic analysis of cell-free culture filtrate showed the presence of tartaric acid, malic acid, citric acid, succinic, and gluconic acid. Tartaric acid was effective in solubilization of tricalcium phosphate. The test strain also produced extracellular phytase (43.05 EU ml⁻¹) in phytase-specific broth medium. The level of indoleacetic acid (15.59 μg ml ⁻¹) recorded was higher in the absence of tryptophan than in its presence. Seed inoculation with P. striata and its application to soil fertilized with low-grade Mussoorie rock phosphate at 60 kg P₂O₅ ha⁻¹ under pearl millet (Pennisetum glaucum) not only improved the root and shoot biomass (2.01 and 29.12 g pl⁻¹, respectively), but also increased the availability of soil P (43.44 μg g⁻¹) and resulted in higher P uptake by straw and grain. Its application to soil in the presence of rock phosphate provided an option to reduce the input of costly inorganic P fertilizer, as the crop yield in the presence of RP₆₀+ P. striata was comparable with low dose of super phosphate (SP₃₀) + P. striata. The microphos inoculants developed from the bacterial strain with multiple functional attributes can help the marginal farmers replenish the soil P more economically compared with costly inorganic phosphate fertilizer.

Keywords:

• Phosphorus
• phytase
• solubilization
• mineralization
• phytohormones