We describe an ongoing study inspecting the interactions of biota and soil organic matter with phosphorus in open drainage ditches. Through processes of iron reduction, chelation of aluminum and iron by organics, competition for sorption sites between organics and phosphorus, and iron mineral transformations, the presence of soil organic matter may help or hinder the retention of phosphorus in open drainage ditches. Biota uptake phosphorus when active and release it upon senescence. In two heavily instrumented and sampled drainage ditches on the Eastern Shore of Maryland we inspect these mechanisms for their importance in P transport. Ditch water pH, temperature, dissolved oxygen and soil redox potential are monitored continuously, and ditch soil is periodically sampled for soil organic matter characters, and soil properties important to P transport. Of particular interest is the onset of storm flow, when water chemistry may change markedly.