A sediment phosphorus model, describing dynamics of organic phosphorus, dissolved reactive phosphorus and exchangeable particulate phosphorus, is applied to five monitoring stations in Chesapeake Bay, USA, to examine model performance in predicting sediment-water phosphorus exchange. The model was fit to 1 year of field measurements, and verified over 3 years at five sampling stations. The results show that the simulated concentrations of phosphorus reasonably correspond to model mechanisms and field observations in both spatial and temporal variations. Predicted release fluxes of phosphorus are consistent with field measurements and improved over those obtained by existing sediment phosphorus models. The model incorporates the effects of dissolved oxygen and non-linear, non-equilibrium sediment sorption in phosphorus dynamics. A sensitivity analysis indicates the importance of the non-linear, non-equilibrium sorption processes to accurate prediction of sediment-water phosphorus flux.