Sediment and phosphorus loss in runoff from an agroforestry catchment, NW Spain

Abstract This study was conducted to evaluate the factors controlling sediment and phosphorus export in a small agroforestry catchment located in NW Spain. At the catchment outlet discharge was continuously measured and suspended sediment (SS) and total (PT), particulate phosphorus (PP) and dissolved phosphorus (DP) were determined during seven rainfall events occurred in autumn. Sediment and sediment‐associated P export differed significantly between events. Particulate P was a greater portion of P transported in runoff. A large proportion of SS and PP exported from the catchment occurred from a relatively small portion of the catchment and during only two events. Rills and gullies delivered most of the eroded sediment directly to the stream, which contribute to high sediment and phosphorus exportation at the catchment outlet. Strong correlations between P and SS concentrations suggest that erosion processes are important in P fluxes. The highly significant correlation between SS and P concentrations in the stream enables to estimate transported P using SS in the Corbeira catchment. Copyright © 2009 John Wiley & Sons, Ltd.