Soil Phosphorus Compositional Characteristics as a Function of Land-Use Practice in the Upper Eau Galle River Watershed, Wisconsin

摘要

The purpose of this research was to quantify biologically labile and refractory phosphorus species in source soils of an agricultural watershed that drains into a eutrophic Corps of Engineers reservoir. Eutrophication of receiving waters is strongly linked to the erosion and transport of particulate and soluble nutrients derived from the watershed landscape. In dairy and agricultural settings, amendment of soils with fertilizers and manure is usually based on crop nitrogen (N) requirements rather than phosphorus (P) to obtain optimal yield. In particular, various manures also have a high P content; usually well in excess of crop uptake requirements with N:P ratios near 1 (Powers and Van Horn 1998). Thus, applications based on crop N requirements usually result in the buildup of soil P levels to excessive concentrations that can be transported to receiving waters during storms (Sharpley et al. 1994).