Phosphorous solubilizersare microrganisams that can make available phosphorous to plant. Example: Bacillus megatherium var. phosphaticum and Pseudomonas striata.

They produce organic acids (viz, citric acid, succinic acid, lactic acid, etc.), hormones (viz, indole acetic acid, gibberellins etc.) and enzymes (viz, phytase, nuclease, lecithinase etc.). This help in solubilisation of insoluble phosphates into plant utilizable form.

They are recommended mainly for upland crops raised in neutral and slightly alkaline soils. They enable efficient utilization of insoluble or fixed phosphate by crop plants.

Commercially it is available as carrier based inoculum.The recommended method of application includes seed treatment, seedling dip and direct soil application along with organic manure.

Take 500gram culture in a plastic tray/basin. Moisten it by sprinkling water or rice-gruel water (500 ml). Add moistened seeds, mix well and dry under shade for 30 minutes. The treated seed should be sown immediately.

For seedling dip the slurry of the culture may be prepared by mixing 500g culture with 2.5 litre of water. The roots of the seedlings are dipped in the slurry for 15-20 minutes before transplanting.

For soil application one kilogram of the culture is mixed with 25 kilogram of FYM or compost and applied directly in the soil.For crops of six-month duration, the recommended dose is 1-2 kg/ha. This can be increased to 2-4 kg/ha for crops with more than six months duration.

For perennial crops, 10 to 25 gram of the bio fertilizer is to be applied in the root zone during the first year and 25 to 50 gram during subsequent years. This can be done at the time of sowing, transplanting or during intercultivation.