Technical Abstract: Ditches provide vital drainage to coastal plain soils subject to high water tables. However, there is a limited understanding of the role that drainage ditches play in the transfer of nutrients from agricultural fields to downstream water bodies. This project saught to elucidate the role of specific processes on ditches as conduits, sources and sinks of agricultural phosphorus. Monitoring stations were installed in eight ditches on the University of Maryland Eastern Shore research farm (Princess Anne, MD). Ditch flow and water quality have been monitored since 2001 in two ditches and since 2005 in the remaining ditches. Large losses of phosphorus were recorded from the drainage ditches, with most phosphorus exported in storm flow. Particulate and dissolved forms of phosphorus in ditch flow were of equal import. Surface runoff from adjacent fields served as a relatively minor source of phosphorus in ditch flow, pointing to groundwater and ditch sediments as likely sources of phosphorus in ditch effluent.