Abstract: The results showed that by increasing the time of incubation, P availability in soil gradually decreased for both organic (DCP) and inorganic (SSP) sources. Phosphorus sorption irrespective of source, however, increased with incubation time. SSP compared to DCP yielded more AB-DTPA extractable P up to day 7, P content of SSP after day 14 became equal to that of DCP, and there after declined. After day 56, as much as half of P from SSP was sorbed out compared to 1/4th of P from DCP. Thus a readily soluble P source (SSP) was more affected to sorption under an alkaline calcareous soil environment compared to slowly soluble P source (DCP) which maintained P availability in soil for a longer period of time.