Total phosphorus determination of select Mollisol soils for use in agricultural non-point source (AGNPS) modeling

CHED 1153

Jesse Voelker, voelkej1@southwestmsu.edu and Frank V. Schindler, schindlerfr@southwestMSU.edu. Department of Chemistry, Southwest Minnesota State University, 1501 State Street, Marshall, MN 56258
Total Maximum Daily Load (TMDL) is a term used to describe the amount of pollution a stream can receive and still meet water quality standards. Computer models are often used to evaluate if TMDLs are being met. Agricultural Non-Point Source (AGNPS) is a data intensive watershed model that routes sediment and nutrients through a watershed by utilizing land uses and topography. Since Phosphorus (P) is considered an essential algal nutrient and thus a major contributor to water resource eutrophication, P is an essential nutrient input parameter of AGNPS. Based on the results generated from AGNPS, Best Management Practices (BMPs) are implemented in the critical areas to alleviate P loading to watershed outlets. There is little total P data available for the representative soils of this region. Consequently, total P was determined for select mollisol soils of South Dakota and Western Minnesota. Total P was determined using mixed sulfuric and hydrofluoric acid digestion and ascorbic acid colorimetric procedures. Total P values relative to the current AGNPS watershed model and their correlation to the standard Olsen-P index for agronomic P are discussed.