Measuring and modeling watershed phosphorus loss and transport for improved management of agricultural landscapes

Phosphorus (P) is a primary cause of eutrophication in aquatic ecosystems. Excess P, and associated impacts of eutrophication, are the most pervasive and widespread causes of degradation of freshwaters, resulting in loss of biodiversity, impairment of water quality, and reduction of services provided by streams, rivers and lakes. Nonpoint sources of P and, in particular, transport of P from agricultural fields to streams and lakes, is the most widespread pathway for P movement in many watersheds of Minnesota. Control of erosion on farms has led to a reduction in losses of particulate (sediment bound) P from agricultural fields. However excess P continues to plague Minnesota's freshwaters, posing a serious management challenge because processes that control its transport and transformation at the watershed scale are not thoroughly known, and climate trends are likely to accelerate eutrophication. This project integrated complementary approaches, combining analyses of large water quality monitoring datasets, new field measurements, sediment and P budget analyses and modeling to understand the sources, magnitude and controls over river P transport in Minnesota's agricultural landscapes.