Increasing emphasis on phosphorus (P)-based nutrient management underscores the need to understand P transport in soils amended with P fertilizer sources. The objectives of this study were i) to evaluate the water extractable P (WEP) in P source materials as a predictor of P leaching loss and ii) to characterize source-derived P transport by leaching in relation to the Langmuir sorption parameters. The miscible displacement of P under unsaturated condition was performed on repacked soil columns (6.35-cm diameter and 10-cm length) using seven P source materials: poultry compost (PC), poultry litter (PL), swine lagoon sludge (SS), triplesuperphosphate (TSP), dairy lagoon liquid (DL), swine lagoon liquid (SL), and dissolved KH₂PO₄ (KP). When these P sources were surface-applied on a total P basis (75 and 150 kg ha^-1) as a pulse, inorganic P sources (TSP and KP) showed about two-fold greater P loss than organic P sources (DL, PC, PL, SL, and SS). The loss of source-derived P was well correlated with WEP in source materials (r² = 0.87). For the columns treated with liquid P sources (DL, KP, and SL), we extrapolated one-dimensional P breakthrough curves (BTCs) from the Langmuir sorption parameters and the one-dimensional convective-dispersive equation model, and compared them with measured P BTCs. Enhanced P transport was observed in the columns treated with DL and SS as compared to KP. Results indicated that enhanced P transport in DL and SS may be attributable to the competition between DOC and P for sorption sites and mineralization of organic P.