Soil legacy phosphorus (P) accumulated due to the long-term continuous application of phosphatic fertilizers in agricultural fields retained in the soil for years, as they are sparingly soluble. This can be made as a possible soil P source using phosphorus activators. In this study, a laboratory incubation and a pot experiment was conducted to evaluate the potential of some P activators (Phosphorus Solubilising Bacteria, Phytase, Humic acid, Oxalic acid, Farmyard Manure) in increasing the availability of residual phosphorus in calcareous soil. For incubation experiment, the P activators were applied alone and combined. Soil samples were analyzed at subsequent intervals for Olsen P, alkaline phosphatase activity, and sequential P fractions. The results showed that Farmyard Manure (FYM) application with Humic acid (HA) increased the available soil phosphorus and alkaline phosphatase activity. All treatments have a significant effect on different soil P-fractions. A greater reduction in calcium phosphate fraction was noted in FYM and Humic acid application. The best five treatments selected from the laboratory incubated experiment were used for the pot experiment with maize, along with the different dosages of P fertilizer. The morphological parameters were observed on 30th and 60th days of the maize crop. The results show that the application of FYM and Humic acid with 100% recommended dose of P was statistically comparable with FYM and Humic acid with 75% recommended dose of P. The findings have illustrated the potential mechanisms of P release by different P activators and the efficiency of P activators in increasing the legacy P availability.