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FIELD SCALE APPLICATION OF A WATER QUALITY MODELING APPROACH FOR ALTERNATIVE AGRONOMIC PRACTICES

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Watershed Management to Meet Water Quality Standards and Emerging TMDL (Total Maximum Daily Load) Proceedings of the Third Conference 5-9 March 2005 (Atlanta, Georgia USA) Publication Date 5 March 2005  701P0105.(doi:10.13031/2013.18092)
Authors:   V. Nangia, P. Gowda, D. Mulla, G. Sands
Keywords:   Water quality, ADAPT, GIS, fertilizer management, tile drainage

This paper evaluates the effectiveness of alternative agronomic practices at improving water quality in agricultural fields. A spatial process model was calibrated using monthly flow and NO3-N losses from a 14 ha commercial farm in southeastern Minnesota. The study area was monitored for NO3-N losses from 1999-2003. Spatial patterns in crops, topography, fertilizer applications and climate were used as input to drive the model. Monitoring data from 1999-2001 were used for calibration and data from 2002-2003 were used in validation of the model. For the calibration period, the observed and predicted flow and NO3-N discharges were in good agreement with r2 values of 0.86 and 0.86, respectively. During validation, the observed and predicted flow and NO3-N discharges were in excellent agreement with r2 values of 0.92 and 0.91, respectively. The calibrated model was used to evaluate the effects of rate and timing of N fertilizer application on NO3-N losses. Reductions in NO3-N losses are possible by changing the application timing from fall to spring. For an application rate of 180 kg/ha (160 lb/ac), there was an 8% reduction in NO3-N losses when switching from a fall to spring application. Further reductions in NO3-N losses require reductions in N application rates. A twelve percent reduction in nitrate losses was found when the application rate was reduced from 180 kg/ha (160 lb/ac) to 135 kg/ha (120 lb/ac)

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