Question

Epa method of determination of available phosphorus in soil using stannous chloride method

Answer 1

The term available phosphorus refers to the inorganic form occurring in soil solution which is almost exclusively ‘Orthophosphate’. This Orthophosphate occurs in several forms and combinations. The phosphate contributions in soil are governed by hydrogenous equilibria in which it takes part. This can be represented as,Phosphorus absorbed in soil phase ⇌ P in soil solution ⇌ Precipitated The phosphorus absorbed by plants from soil comes from the soil solution in which it exists as an inorganic Orthophosphate ion H2PO4-, HPO42- and PO43-. The most accessible ion is H2PO4-. The quality of phosphorus accessible to the plants is influenced by a series of soil properties.