Effect of phosphorus sources on inorganic P fractions, Olsen-P, yield and P uptake by pigeonpea and groundnut in Vertisol and Alfisol.

A greenhouse experiment was conducted on Otur and Nimone soil series of Vertisol and Wakavali soil series of Alfisol. An application of KH 2 PO 4 recorded significantly highest inorganic P fractions, Olsen-P, yield and P uptake over AlPO 4 , Ca 3 (PO 4 ) 2 and FePO 4 by both legumes. Among the insoluble P sources Ca 3 (PO 4 ) 2 was found to be significantly better than AlPO 4 or FePO 4 for groundnut and FePO 4 for pigeonpea. Both the soil series of Vertisol proved significantly better than Wakavali soil series of Alfisol for inorganic P fractions, Olsen-P. dry matter yield and P uptake by pigeonpea and groundnut. The coefficient of correlation (r) between yield. P uptake and Olsen-P were highly correlated with the different inorganic P fractions in soils barring few exception for both legumes ( r - 0.6* to 0.96**). Among the different inorganic P fractions of Vertisol Ca-P was the most important P fraction for P nutrition of groundnut while it was Fe-P fraction for pigeonpea. In Alfisol RS-P was the best closely followed by Ca-P for P nutrition of pigeonpea, while Fe-P was the best closely followed by Ca-P for P nutrition of groundnut.