Premium
Southern Phosphorus Indices, Water Quality Data, and Modeling (APEX, APLE, and TBET) Results: A Comparison
Author(s) -
Osmond Deanna,
Bolster Carl,
Sharpley Andrew,
Cabrera Miguel,
Feagley Sam,
Forsberg Adam,
Mitchell Charles,
Mylavarapu Rao,
Oldham J. Larry,
Radcliffe David E.,
RamirezAvila John J.,
Storm Dan E.,
Walker Forbes,
Zhang Hailin
Publication year - 2017
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2016.05.0200
Subject(s) - environmental science , phosphorus , index (typography) , water quality , south carolina , hydrology (agriculture) , geology , ecology , chemistry , geotechnical engineering , organic chemistry , public administration , world wide web , computer science , political science , biology
Phosphorus (P) Indices in the southern United States frequently produce different recommendations for similar conditions. We compared risk ratings from 12 southern states (Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, and Texas) using data collected from benchmark sites in the South (Arkansas, Georgia, Mississippi, North Carolina, Oklahoma, and Texas). Phosphorus Index ratings were developed using both measured erosion losses from each benchmark site and Revised Universal Soil Loss Equation 2 predictions; mostly, there was no difference in P Index outcome. The derived loss ratings were then compared with measured P loads at the benchmark sites by using equivalent USDA–NRCS P Index ratings and three water quality models (Annual P Loss Estimator [APLE], Agricultural Policy Environmental eXtender [APEX], and Texas Best Management Practice Evaluation Tool [TBET]). Phosphorus indices were finally compared against each other using USDA–NRCS loss ratings model estimate correspondence with USDA–NRCS loss ratings. Correspondence was 61% for APEX, 48% for APLE, and 52% for TBET, with overall P index correspondence at 55%. Additive P Indices (Alabama and Texas) had the lowest USDA–NRCS loss rating correspondence (31%), while the multiplicative (Arkansas, Florida, Louisiana, Mississippi, South Carolina, and Tennessee) and component (Georgia, Kentucky, and North Carolina) indices had similar USDA–NRCS loss rating correspondence—60 and 64%, respectively. Analysis using Kendall's modified Tau suggested that correlations between measured and calculated P‐loss ratings were similar or better for most P Indices than the models. Core Ideas Southern region P Indices estimate P losses as well as water quality models. APLE and TBET P‐loss predictions were more similar than were results from APEX. Assigning potential P‐loss risk from P Indices to any given water resource is challenging.