1 Variations in Field-Scale Nitrogen and Phosphorus Concentrations in Runoff as a Function of Land-Use Practice

PURPOSE: The purpose of this research was to examine nitrogen and phosphorus concentrations in runoff at the field-scale level (i.e., homogeneous land-use plot) over a variety of land-use practices. Land-use practices included animal containment/barnyard areas, corn production fields, alfalfa and grass hayfields, Conservation Reserve Program (CRP) fields, and woodlots located in the upper Eau Galle River Watershed, west-central Wisconsin. The watershed is dominated by agricultural and dairy livestock land-use practices. Results from this study will be important in improving watershed modeling capabilities for predicting the runoff of nutrients from complex landscape mosaics. BACKGROUND: Transformations and fluxes of nitrogen (N) and phosphorus (P) forms from the landscape are dictated by many complex factors including agricultural management practices, soil erosion and overland runoff potential, soil type, and soil nutrient concentration (Lemunyon and Gilbert 1993; Sharpley 1995). In particular, management of soils for crop production via fertilization and manure application can result in nutrient storage in the soil in excess of crop demand (particularly for P), leading to enhanced potential for soil nutrient loss during overland flow (Sims 1993; Sharpley et al. 1996) and accelerated eutrophication o