Processes controlling soil phosphorus release to runoff and implications for agricultural management

Phosphorus (P) loss from agricultural land to surface waters is well known as an environmental issue because of the role of P in freshwater eutrophica tion. Much research has been conducted on the erosion and loss of Pin sedim ents and surface runoff. Recently, P loss in sub-surface runoff via agricul tural drainage has been identified as environmentally significant. High soi l P levels are considered as a potential source of P loss. However, without favourable hydrological conditions P will not move. In this paper, we revi ew the basis of soil P release into solution and transport in surface and s ub-surface runoff. Our objectives are to outline the role of soil P and hyd rology in P movement and management practices that can minimize P loss to s urface waters. Remedial strategies to reduce the risk of P loss in the shor t-term are discussed, although it is acknowledged that long-term solutions must focus on achieving a balance between P inputs in fertilizers and feed and P outputs in production systems.