Abstract: This study investigated effects of incubation period on Phosphorus (P) release from selected P-sources. The latter are reported to improve levels of P in highly weathered Chromic Acrisol, which has been under continuous cultivation. The study was based on screen-house which utilized Minjingu Mazao (MM) fertilizer, Cattle (CM) and Poultry (PM) manures. The MM fertilizer was applied at 0.258 g per 4 kg soil, equivalent to 40 kg P ha-1. Cattle manure and PM were incorporated in soils with and without MM at 10 g per 4 kg soil. The incubation went through 14, 28 and 42 days and P was analyzed after every incubation period. Results showed that incubating the soil with deionized water for 14 days adjusted P from 7.9 to 8.4 mg kg-1 soil. The MM, PM and CM increased P to 12.2, 15.9 and 17.9 mg kg-1, respectively. In addition, MM+CM, MM+PM increased P to 16.1 and 14.2 mg kg-1, respectively. Initially, P increased significantly (p <0.001) but later decreased substantially beyond 14 days. However, PM and CM gave relatively promising P values between 14 and 28 days as opposed to 42 days of incubation. It was concluded that incubating cattle manure and incorporating it with Minjingu Mazao fertilizer provides promising P quantities indicating high rates of P depletion in soils. Incubating soil with poultry manure and incorporating Minjingu Mazao fertilizer had slow release of P hence, might benefit a slow growing crop.