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Title: Watershed-level comparison of predictability and sensitivity of two phosphorus models
Authors: Sen S.
Srivastava P.
Vadas P.A.
Kalin L.
Published in: Journal of Environmental Quality
Abstract: Buildup of phosphorus (P) in agricultural soils and transport of P to nearby surface waters due to excessive, long-term application of poultry litter is an environmental concern in many poultryproducing states. Watershed models are often used to quantify soil and water quality impacts of poultry litter applications. However, depending on how P transport is simulated in watershed models, the anticipated impact could be quite different. The objective of this study was to determine thepredictability and sensitivity of the Soil and Water Assessment Tool (SWAT) P model and a newly developed, state-of-the-art manure P model called SurPhos in a poultrylitter-applied pasture watershed. A small, predominantly agricultural watershed in Randolph County, Alabama was used for this study. The SWAT model, calibrated for surface runoff and total stream fl ows (Nash-Sutcliffe coefficient of 0.70 for both), was used to provide runoff inputs to the SurPhos model. Total dissolved P (TDP) exports simulated by the SWAT P and SurPhos models from the hay hydrological response units of the watershed were compared for diff erent poultry litter application rates and diff erent initial soil Solution P levels. Both models showed sensitivity to poultry litter application rates, with SWAT simulating linear and SurPhos simulating nonlinear increases in TDP exports with increase in poultry litter application rates. SWAT showed greater sensitivity to initial soil Solution P levels,which can lead to overestimation of TDP exports, especially at low poultry litter application rates. As opposed to the SurPhos model simulations and contrary to recent studies, SWAT simulated excessive accumulation of Solution P in the top 10 mm of soil. Because SurPhos appears to simulate P transport and build-up processes frommanure-applied areas more accurately, this study suggests that SWAT be replaced by SurPhos to more accurately determine watershed-level eff ectiveness of P management measures. © 2012 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.
Citation: Journal of Environmental Quality (2012), 41(5): 1642-1652
Issue Date: 2012
ISSN: 472425
Author Scopus IDs: 15840367400
Author Affiliations: Sen, S., Dep.of Hydrology, Indian Institute of Technology, Roorkee, 247667 Uttarakhand, India
Srivastava, P., Dep.of Biosystems Engineering, Auburn Univ., Auburn, AL 36849, United States
Vadas, P.A., USDA-ARS, Dairy Forage Research Center, Madison, WI 53706, United States
Kalin, L., School of Forestry and Wildlife Sciences, Forestry and Wildlife Building, Auburn Univ., Auburn, AL 36849, United States
Corresponding Author: Sen, S.; Dep.of Hydrology, Indian Institute of Technology, Roorkee, 247667 Uttarakhand, India; email:
Appears in Collections:Journal Publications [HY]

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