Evaluation of Soil Phosphorus Tests and its Relation to Inorganic P forms in Flooded Soils

Field experiments were conducted with rice under flooded condition to evaluate the efficacy of various soil tests for available P. Available P status as estimated by different extractants and its relationship with different inorganic P forms as influenced by various organic manures and P fertilizers under wetland ecosystem is reported.Among different indices of P availability,Olsen’s soil test was found to be the most suitable method.The P extracting power of different extractants was in the order: Mehlich I > Bray I > Truog > Olsen > Morgan. Olsen and Bray No.1 extractants were consistent in extracting P from specific P fractions than the other three extractants. Iron-P was the dominant inorganic P fraction followed by Ca-P, Al-P and saloid-P. Available P in this rice soil depended on the concentration of Fe-P and saloid-P. Inorganic P forms jointly contributed to 94 per cent variations in Olsen-P.