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Simulating Nitrate Drainage Losses from a Walnut Creek Watershed Field
Journal of Environmental Quality
  • Allah Bakhsh, Iowa State University
  • Jerry L. Hatfield, United States Department of Agriculture
  • Ramesh S. Kanwar, Iowa State University
  • Liwang Ma, United States Department of Agriculture
  • Lajpat R. Ahuja, United States Department of Agriculture
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This study was designed to evaluate the improved version of the Root Zone Water Quality Model (RZWQM) using 6 yr (1992–1997) of field-measured data from a field within Walnut Creek watershed located in central Iowa. Measured data included subsurface drainage flows, NO3–N concentrations and loads in subsurface drainage water, and corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yields. The dominant soil within this field was Webster (fine-loamy, mixed, superactive, mesic Typic Endoaquolls) and cropping system was corn–soybean rotation. The model was calibrated with 1992 data and was validated with 1993 to 1997 data. Simulations of subsurface drainage flow closely matched observed data showing model efficiency of 99% (EF = 0.99), and difference (D) of 1% between measured and predicted data. The model simulated NO3–N losses with subsurface drainage water reasonably well with EF = 0.8 and D = 13%. The simulated corn grain yields were in close agreement with measured data with D < 10%. Nitrogen-scenario simulations demonstrated that corn yield response function reached a plateau when N-application rate exceeded 90 kg ha−1 Fraction of applied N lost with subsurface drainage water varied from 7 to 16% when N-application rate varied from 30 to 180 kg ha−1 after accounting for the nitrate loss with no-fertilizer application. These results indicate that the RZWQM has the potential to simulate the impact of N application rates on corn yields and NO3–N losses with subsurface drainage flows for agricultural fields in central Iowa.

This article is from Journal of Environmental Quality 33 (2004): 114–123, doi:10.2134/jeq2004.1140.

Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.
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Allah Bakhsh, Jerry L. Hatfield, Ramesh S. Kanwar, Liwang Ma, et al.. "Simulating Nitrate Drainage Losses from a Walnut Creek Watershed Field" Journal of Environmental Quality Vol. 33 Iss. 1 (2004) p. 114 - 123
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