Phosphorus sorption in soils is influenced by previous P additions. Our objective was to quantify the impact of previous P additions on the sorption of inorganic P and three organic P compounds (adenosine tri-phosphate, glucose 6 phosphate, or inositol hexaphosphate) when added either individually or in combination with each other using 24 hour sorption isotherms. The results and implcations of this study will be presented in this poster.