Chelation: We know from different study that phosphate solubilised by the combined effect of pH decrease and organic acids production (Fankem et al., 2006). PSB produces carboxylic acids which have high affinity to calcium, and is able to solubilize more phosphorus than acidification alone (Staunton and Leprince 1996). Organic anions and associated protons are also effective in solubilizing precipitated forms of soil P (e.g. Fe - and Al - P in acid soils, Ca - P in alkaline soils) through chelation of metal ions and facilitate the re-lease of adsorbed P through ligand exchange reactions (Jones, 1998).Rayan et al (2001) showed that phosphorus desorption potential of different carboxylic anions lowers with decrease in stability constants of Fe - or Al - organic acid complexes (log KAl or log KFe) in the order: citrate > oxalate > malonate / malate > tartrate > lactate > gluconate > acetate > formiate .

Acid action: Oxidation of nitrogenous and inorganic S compounds produces inorganic acids like nitric acids and sulphuric acids, which react with rock phosphate and increase soluble P (Martins., 2011).

Microbial release of CO2: In calcareous soil P solubility is governed by CO2 production by microbes. Lindsay (1979) established the equation logH₂PO₄ - logPco₂ =-9.23+pH, which implies that at any given pH Increase in concen-tration of CO2 will also increase the solubility of H₂PO₄ by decreasing the activity of Ca2+ in soil by formation of CaCO3. Tang et al (2014) showed that in rhizosphere of wheat, lentil, and chickpea, intercrop wheat-chickpea and intercrop wheat-lentil than bulk soil due to the higher activity of microbes and subsequent release of CO2.

Chelation: We know from different study that phosphate solubilised by the combined effect of pH decrease and organic acids production (Fankem et al., 2006). PSB produces carboxylic acids which have high affinity to calcium, and is able to solubilize more phosphorus than acidification alone (Staunton and Leprince 1996). Organic anions and associated protons are also effective in solubilizing precipitated forms of soil P (e.g. Fe - and Al - P in acid soils, Ca - P in alkaline soils) through chelation of metal ions and facilitate the re-lease of adsorbed P through ligand exchange reactions (Jones, 1998).Rayan et al (2001) showed that phosphorus desorption potential of different carboxylic anions lowers with decrease in stability constants of Fe - or Al - organic acid complexes (log KAl or log KFe) in the order: citrate > oxalate > malonate / malate > tartrate > lactate > gluconate > acetate > formiate .

Acid action: Oxidation of nitrogenous and inorganic S compounds produces inorganic acids like nitric acids and sulphuric acids, which react with rock phosphate and increase soluble P (Martins., 2011).

Microbial release of CO2: In calcareous soil P solubility is governed by CO2 production by microbes. Lindsay (1979) established the equation logH₂PO₄ - logPco₂ =-9.23+pH, which implies that at any given pH Increase in concen-tration of CO2 will also increase the solubility of H₂PO₄ by decreasing the activity of Ca2+ in soil by formation of CaCO3. Tang et al (2014) showed that in rhizosphere of wheat, lentil, and chickpea, intercrop wheat-chickpea and intercrop wheat-lentil than bulk soil due to the higher activity of microbes and subsequent release of CO2.

Chelation: We know from different study that phosphate solubilised by the combined effect of pH decrease and organic acids production (Fankem et al., 2006). PSB produces carboxylic acids which have high affinity to calcium, and is able to solubilize more phosphorus than acidification alone (Staunton and Leprince 1996). Organic anions and associated protons are also effective in solubilizing precipitated forms of soil P (e.g. Fe - and Al - P in acid soils, Ca - P in alkaline soils) through chelation of metal ions and facilitate the re-lease of adsorbed P through ligand exchange reactions (Jones, 1998).Rayan et al (2001) showed that phosphorus desorption potential of different carboxylic anions lowers with decrease in stability constants of Fe - or Al - organic acid complexes (log KAl or log KFe) in the order: citrate > oxalate > malonate / malate > tartrate > lactate > gluconate > acetate > formiate .

Acid action: Oxidation of nitrogenous and inorganic S compounds produces inorganic acids like nitric acids and sulphuric acids, which react with rock phosphate and increase soluble P (Martins., 2011).

Microbial release of CO2: In calcareous soil P solubility is governed by CO2 production by microbes. Lindsay (1979) established the equation logH₂PO₄ - logPco₂ =-9.23+pH, which implies that at any given pH Increase in concen-tration of CO2 will also increase the solubility of H₂PO₄ by decreasing the activity of Ca2+ in soil by formation of CaCO3. Tang et al (2014) showed that in rhizosphere of wheat, lentil, and chickpea, intercrop wheat-chickpea and intercrop wheat-lentil than bulk soil due to the higher activity of microbes and subsequent release of CO2.

Thank you Sir..

Application of silicic acid also recommended.

Thank you Sir