Accumulation of phosphorus in soil is a major factor limiting the operational life (period of time where the soil can serve as an effective phosphorus sink) of land application waste disposal systems. Better evaluation of phosphorus operational life requires improved understanding of how manure application to soil can affect its phosphorus sorption characteristics. In this study, laboratory experiments were conducted to investigate the impact of feedlot runoff effluent application on phosphorus sorption capacities, equilibrium phosphorus concentrations, and phosphorus buffering capacities of six Iowa soils. Soil samples were collected from vegetative treatment areas that had received feedlot runoff application for the previous five years and from a paired grassed area that did not. Subsamples of each soil were incubated with a series of 12 phosphorus solutions ranging in concentration from 0 to 200 mg P/L to determine the sorption characteristics and results fitted to the Langmuir model to determine the phosphorus equilibrium concentration, phosphorus buffering capacity, and maximum phosphorus sorption capacity. Results indicated that vegetative treatment areas generally had elevated phosphorus equilibrium concentrations, indicating an elevated risk of loss of dissolved phosphorus. In most cases, the ability of the soil to sorb phosphorus was significantly increased, as was the remaining phosphorus sorption capacity of the soil. These results indicate that vegetative treatment area life could be greatly extended due to soil property modifications that occur as a result of system operation.