Phosphorus Loading and Compositional Characteristics in Eight-Mile Run

PURPOSE: The purpose of this research was to describe and quantify biologically labile and refractory phosphorus runoff in Eight-Mile Run, a small watershed in west-central Wisconsin that is impacted by dairy livestock management. BACKGROUND: There is a need to manage eutrophication problems in Corps of Engineers receiving waters by reducing losses of soils and associated soluble nutrients (primarily phosphorus) in intensively managed agricultural land-use settings that are hydrologically sensitive to runoff. In many agricultural watersheds, livestock is contained in relatively small areas for long periods of time, leading to overgrazing and loss of perennial cover, disruption of the soil surface, and the buildup of nutrients in the soil via manure incorporation that can become a source to receiving waters during runoff events. Bank erosion and decimation of adjacent buffer strips by livestock that is allowed to forage along tributaries can further exacerbate soil and nutrient erosion and runoff. To forecast the impacts of watershed rehabilitation and Best Management Practices (BMPs) on hydraulic and nutrient loadings, models need to be refined to address the impacts of various land-use practices such as livestock production and management on concentrations and loads of sediment and important nutrients like nitrogen and phosphorus in rivers and streams draining watersheds