Sediment phosphorus dynamics in tile-fed drainage ditches

Stream sediments may regulate aqueous phase phosphorus (P) concentrations. The objectives of this work were to study the equilibrium P concentrations between the aqueous phase and sediments in tile-fed drainage ditches. Sediments from three ditches in Indiana, USA, were sampled and evaluated as P sources or sinks. Sediments that potentially release P to aqueous solutions could be chemically amended to sequester labile P. Sediment deposition from episodic storm events could increase the P buffering capacity of drainage ditches. In fluvarium studies (initial concentration of 0.55 mM P), aqueous P concentrations after 120 h were 0.075 mM and 0.111 mM for predredged and dredged sediments, respectively. Phosphorus release from sediments to the aqueous solution was greater from the dredged sediments. These studies are expanding our understanding of the dynamic nature of P in agricultural ditches, and aiding in the development of ditch management practices to reduce downstream P transport.