Evaluating a campus nitrogen budget for Auburn University, Alabama, USA

Abstract

Prompted by recent sustainability trends, some institutions and municipalities have begun quantifying their local impact on the nitrogen (N) cycle. To better understand the N budget at Auburn University (AU), we measured N inputs and outputs in four subsystems (near surface atmosphere, human metabolism, animal metabolism, and landscape) utilizing methods established by Savanick et al. (2007) for the University of Minnesota-Twin Cities (UM). The total AU input of 245.7 Mg N yr⁻¹ and total output 217.5 Mg N yr⁻¹ was made up of the balance of subsystem inputs and outputs (near surface atmosphere 174 Mg N yr⁻¹ input, 174 Mg N yr⁻¹ output; human metabolism 22.8 Mg N yr⁻¹ input, 20.5 Mg N yr⁻¹ output; animal metabolism 39.2 Mg N yr⁻¹ input, 20.9 Mg N yr⁻¹ output; landscape 9.7 Mg N yr⁻¹ input, 2.1 Mg N yr⁻¹ output). We compared these results with N balances for UM and the University of Virginia (UVA) (Leach et al. 2013) and found that larger campus area was associated with higher commuter emissions, colder average temperatures were associated with more on-campus energy emissions, presence of agriculture and veterinary schools were associated with larger animal metabolism N flux, and campuses greater urban density or crop presence tended to have greater landscape N flux. We found that overall N flux for each campus was similar when normalized per capita (7–11 kg N cap⁻¹ yr⁻¹). This study provides insight towards reaching sustainability goals at AU and other institutions and can inform decisions regarding pollution reduction plans.