US-IALE 2018

AUTHORS: Quercus Hamlin*, Syracuse University; Anthony Kendall, Sherry Martin, David Hyndman – Michigan State University

ABSTRACT: Anthropogenic alteration of nitrogen and phosphorus cycling is a worldwide problem affecting water bodies at all scales. Landscape inputs such as fertilizer, livestock manure, and human waste have led to eutrophication creating biologically, economically, and environmentally hazardous harmful algal blooms (HABs). Management plans for nutrient load reduction would benefit from regionally-consistent, locally-relevant, fine scale nutrient application maps. We developed the Spatially Explicit Nutrient Source Map (SENSMap), a series of high resolution (30 m) N and P landscape application maps, to understand the composition and magnitude of landscape nutrient applications across the Great Lakes Basin. These maps model and distribute 6 nonpoint nutrient sources along with point sources using broadly available data. Nonpoint sources modeled include chemical agricultural fertilizer, chemical non-agricultural fertilizer, atmospheric deposition, septic tanks, manure, and nitrogen fixation from legumes. We combine data from government, literature, and remote sensing platforms using statistical and machine learning methods to distribute loads across the landscape. Once placed, applications can be aggregated and analyzed at any management scale across the Great Lakes Basin (GLB).Here, we describe the SENSMap methodology and identify key trends and relationships within and across land use categories. For instance, we find that 60-80% of N and P inputs in the GLB are from agricultural sources, and that the dominant source within watersheds varies among chemical fertilizers, manure, and nitrogen fixation. This has relevance for biogeochemical cycling, as each of these sources vary greatly in terms of N speciation, N to P ratios, and organic carbon.