Flow effects on phosphorus loss in overland flow

Field studies have demonstrated an increase in dissolved reactive phosphorus (DRP) concentration in overland flow with an increase in overland flow rate. This is counter-intuitive, as due to dilution, a decrease in P concentration would be expected. This research investigates the impact of the expansion of a variable source area (VSA) during a rainfall event on DRP concentration in overland flow. Intact soil sods were taken from an agricultural grassland soil and placed within a 2.1 m long laboratory flume. The laboratory flume was used to simulate overland flow and the expansion of a VSA. The results demonstrated that as flow path length increased there was a corresponding increase in DRP concentration in overland (p < 0.01). An increase in flow rate resulted in a decrease in DRP concentration in overland flow (p < 0.01). When flow path length was increased in conjunction with flow rate DRP concentration increased despite the impact of dilution.