Drainage ditches are an integral component of water management on the lower Eastern Shore of Maryland and share many characteristics with wetlands. Among these characteristics is an accumulation of organic materials in the upper horizons of the soil profile. These “O” horizons are found to be very reactive with respect to phosphorus (P), with enhanced iron, aluminum and P contents. We describe an experiment where intact profiles of ditch soil are subjected to soil horizon and hydrologic treatments designed to indicate the importance of soil O horizons and other horizons to the adsorption/release of P from rising ground water. The retention/release of P from soil mesocosms will be related to horizon type, horizon thickness, individual horizon P sorption characteristics, and the redox status of in situ soil horizons.