Minnesota Phosphorus Loss: How Soil Loss Is Only Part of the Story and Why Modeling Can Be Improved by Considering Subsurface Phosphorus Loss

Abstract

This study explores 20 years of Minnesota regional phosphorus (P) management data across agricultural landscapes and how these are modeled by the Minnesota Phosphorus Index (MNPI). Nutrient-loading and farm management records from 1999-2019 were compiled across 17 different Minnesota counties representing 5 different state regions, including sites from Discovery Farms of Minnesota, Minnesota Department of Agriculture, Minnesota Agricultural Water Resource Center, and the University of Minnesota. The consolidated data cover two critical watersheds in nutrient management, one flowing north to Canada's Lake Winnipeg, the other flowing south through the Mississippi River ultimately to the Gulf of Mexico. Best management practices are needed for P loss within these watershed basins due to rising concerns about recurrent algal blooms in both watersheds. This study combines historical nutrient-loading data and farm management data to see how soil loss due to erosion impacts P losses and how the MNPI models P-loss risk.