Various composts often used as soil amendments and fertilizers may vary in phosphorus (P) status and its transformation pathways after application to soils, which are key factors controlling P bio-availability and loss vulnerability from soil to water. We characterized compost P and assessed the changes in soil P fractions as related a compost addition in a Brookston clay loam soil under continuous corn (Zea mays L.) from 1998 to 2000. The composts investigated were yard waste compost (YWC), swine manure compost (SMC), and food waste compost (FWC). Soil P was sequentially separated into various inorganic (Pi) and organic P (Po) fractions. Regardless of the compost source, HCl-P (moderately stable P) was the predominant P forms, followed by NaHCO3-Pi (labile P) and Res-P (stable P). Added composts increased NaHCO3-Pi, NaOH-Pi (moderately labile P), and HCl-Pi, in the order of SMC>>YWC>FWC, but had subtle effects on NaOH-Po. Increases in soil Pi fractions followed the order of NaHCO3-Pi>NaOH-Pi>HCl-Pi. However, added SMC significantly decreased soil NaHCO3-Po and slightly increased Res-P, while the reverse pattern was found with FWC and YWC. Changes of soil P in the plough layer accounted for 44-74% of the P applied, suggesting that soil P downward movement and subsurface tile drainage loss may have been significant in this flat cracking high textured soil. Effects of compost application on soil P varied with compost type and soil P form, with SMC causing the most significant increases in Pi fractions ranging from labile to moderately stable Pi. Phosphorus-based compost application strategy should be developed by considering both short- and long-term effects on soil P.