Technical Abstract: Drainage ditches can be a key conduit of phosphorus (P) between agricultural soils of the Atlantic coastal plain and local surface waters, including the Chesapeake Bay. This study sought to quantify the effect of a common ditch management practice, sediment dredging, on fate of P in drainage ditches. Sediments from two drainage ditches that had been monitored for seven yrs and had similar characteristics (flow, P loadings, sediment properties) were sampled (0-5 cm) after one of the ditches was dredged to remove fine textured sediments (clay = 41%) with high organic matter content (85 g kg-1) and expose coarse textured sediments (clay = 15%) with low organic matter content (2.2 g kg-1). Sediments were subjected to a three phase experiments (Equilibrium, Uptake and Release), in recirculating 10-m-long, 0.2-m-wide to a 5-cm depth flumes to evaluate their role as sources and sinks of P. Under conditions of low initial P concentrations in flume water, sediments from the dredged ditch released 13 times less P to the water than did sediments from the ditch that had not been dredged, equivalent to 24 kg dissolved P. However, the sediments from the dredged ditch removed 19% less P (76 kg) from the flume water when it was spiked with dissolved P to approximate long-term runoff concentrations. Irradiation of sediments to destroy microorganisms revealed that biological processes accounted for up to 30% of P uptake in the coarse textured sediments of the dredged ditch and 18% in the fine textured sediments of the undredged ditch. Results indicate the potential for dredging of coastal plain drainage ditches to potentially impact the P buffering potential of ditches draining agricultural soils with a high potential for P runoff.