Research Article Open Access

Evaluation of Alternative Cropping and Nutrient Management Systems with Soil and Water Assessment Tool for the Raccoon River Watershed Master Plan

Philip Gassman1, Manoj Jha2, Calvin Wolter3 and Keith Schilling4
  • 1 Iowa State University, United States
  • 2 North Carolina A&T University, United States
  • 3 502 E 9th Street, United States
  • 4 115 Trowbridge Hall, United States

Abstract

The Soil and Water Assessment Tool (SWAT) ecohydrological model was used to assess a suite of adaptive nutrient management, alternative cropping system and combination scenarios in support of a Master Plan that was developed to help guide policy makers, land owners and other stakeholders in improving water quality for the 9,400 km2 Raccoon River watershed in west central Iowa, located in the Corn Belt region of the United States. Calibration and validation of SWAT showed that the model was able to accurately replicate most streamflow and pollutant loss conditions, with r2 and Nash-Sutcliffe modeling Efficiency (NSE) statistics exceeding 0.5 for the majority of indicators. The largest reduction in predicted nitrate losses at the overall watershed scale for the adaptive nutrient management scenarios was slightly over 12%, in response to a scenario in which 100% of the anhydrous ammonia fertilizer application was applied in the watershed four weeks after planting of corn. Considerably larger impacts on nitrate loss and other sediment and nutrient indicators, with some reductions exceeding 50%, were predicted for scenarios representing widescale conversion of corn-soybean rotations to six-year rotation of Corn-Soybean-Corn-Alfalfa-Alfalfa-Alfalfa (CSCAAA) or combinations of adaptive nutrient management, conversion to CSCAAA rotations and the insertion of a rye cover crop on a portion of the area managed with corn and soybean within the CSCAAA rotations.

American Journal of Environmental Sciences
Volume 11 No. 4, 2015, 227-244

DOI: https://doi.org/10.3844/ajessp.2015.227.244

Submitted On: 27 February 2015 Published On: 9 September 2015

How to Cite: Gassman, P., Jha, M., Wolter, C. & Schilling, K. (2015). Evaluation of Alternative Cropping and Nutrient Management Systems with Soil and Water Assessment Tool for the Raccoon River Watershed Master Plan. American Journal of Environmental Sciences, 11(4), 227-244. https://doi.org/10.3844/ajessp.2015.227.244

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Keywords

  • SWAT Model
  • Water Quality
  • Nutrient Management Practices
  • Extended Rotations
  • Winter Cover Crops