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Title: PAIRED WATERSHED MODELING OF SPATIALLY VARIABLE NITRATE LOSSES IN WALNUT CREEK, IA

Author
item GOWDA, P H - UNIVERSITY OF MN
item MULLA, D J - UNIVERSITY OF MN
item Jaynes, Dan

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/25/2001
Publication Date: 10/25/2001
Citation: GOWDA, P., MULLA, D., JAYNES, D.B. PAIRED WATERSHED MODELING OF SPATIALLY VARIABLE NITRATE LOSSES IN WALNUT CREEK, IA. AGRONOMY ABSTRACTS. 2001. CD-ROM. MADISON, WI. ASA-CSSA-SSSA.

Interpretive Summary:

Technical Abstract: A 365 ha agricultural watershed in Walnut Creek, IA was monitored for nitrate losses from 1992-1997. Spatial patterns in crops, soils, fertilizer and manure applications, topography, and climate were used as input data to drive a spatial process model which simulates erosion, runoff, drainage, evapotranspiration, and nitrate fate and transport. Half the monitored data was used for calibration of the model, the other half was used for validation. During the calibration period, observed and predicted nitrate losses in the watershed were in excellent agreement, with an r2 coefficient of 0.74. During the validation period, observed and predicted nitrate losses were in good agreement, with an r2 coefficient of 0.47. For all six years of data, observed nitrate losses averaged 24 kg/ha/yr, while predicted losses were 25 kg/ha/yr. The calibrated model was used to investigate the impacts on nitrate losses of alternative management scenarios including changes in rate and timing of nitrogen fertilizer and manure applications.