Current restoration efforts for the Chesapeake Bay watershed mandate reducing nutrient and sediment loads to receiving waters. The Chesapeake Bay Watershed Model (WSM) estimates loading; however, some WSM routines have not been updated to reflect recent research. This study's objective was to improve the simulation of soil phosphorus dynamics by using an independent modeling tool (APLE) as an alternative to the current WSM approach. Identical assumptions of acreage, soil properties, nutrient management, and transport factors from the WSM were used as inputs to APLE. Outcomes represent revised estimates of phosphorus edge-of-field losses and estimates of change in soil labile phosphorus concentration. The modification resulted in a greater mean phosphorus loss estimate compared to the WSM, and a relationship between nutrient application, tillage, and soil phosphorus concentrations. Outcomes support APLE as an appropriate alternative model for simulating soil phosphorus dynamics, and for informing mitigation of soil phosphorus losses through best management practices.