Dissolution and Transformation of Indigenous Rock Phosphates in an Acid Alfisol

Dissolution and transformation of three major indigenous rock phosphates (Udaipur rock phosphate, Mussoorie rock phosphate and Purulia rock phosphate) at different P levels and soil water regimes in an acid Alfisol were studied in the laboratory. The dissolution of rock phosphate as assessed by different extractants followed the order, Olsen's P > Bray P1 > CSP > WSP. Rock phosphates by and large had similar effects. However, water soluble source (superphosphate) had an edge in dissolution over rock phosphate sources. The transformation of applied P through superphosphate androck phosphate to inorganic P fractions in the incubated soil, followed the order: Fe-P > Al-P > Ca-P. Superphosphate treatment recorded higher values of inorganic P fractions and rock phosphate sources were at par. The results indicate the dominance of Fe-P fraction in acid soils developed under high rainfall conditions and also show that Olsen's P, Bray P1. CSP and WSP were significantly and positively correlated with inorganic P fractions in the soil.