Submitted to: ASAE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 7/17/2005
Publication Date: 7/17/2005
Citation: Nangia, V., Gowda, P., Mulla, D.J., Kuehner, K. 2005. Evaluation of predicted long-term water quality trends to changes in N fertilizer management practices for a cold climate. In: American Society of Agricultural Engineers Annual International Meeting Technical Papers, July 17-20, 2005, Tampa, Florida. Paper Number 052226. 2005 CDROM.
Interpretive Summary: The Minnesota River Basin, with more than 30 percent of its crop land artificially drained, has been identified as one of several relatively high contributors of nitrogen into the Mississippi River. The Mississippi River/Gulf of Mexico Watershed Nutrient Task Force set a coastal goal of reducing areal extent of hypoxia in the Gulf to 5,000 sq. km. by 2015. They estimated that this would require a 30 percent reduction in nitrogen discharges from the Mississippi and Atchafalaya Rivers to the Gulf. A modeling study was conducted to evaluate the reductions in nitrate losses possible with several alternative nutrient management practices on a small agricultural watershed in south-central Minnesota. Simulated results indicated that the recommended reduction in nitrate losses can be achieved just by switching the timing of fertilizer application for fall to spring.
Technical Abstract: Objectives of this study were to calibrate and validate a water quality model for monthly flow and NO3-N losses, and evaluate a set of alternative nutrient management practices to reduce NO3-N losses in an agricultural watershed. A dynamic watershed scale spatial modeling approach that uses ADAPT, a field scale model and GIS was calibrated to predict monthly flow and NO3-N losses from a sub-watershed of Seven Mile Creek in south-central Minnesota. It is a 4029-ha watershed with over 85% of the total area under agriculture. Calibration and validation of the model were done using monitoring data from 2000-2002 and 2003-2004, respectively. For the calibration period, the model predicted mean monthly flow and NO3-N losses of 0.38 m3/s and 4.04 kg/ha, respectively, against measured flow and NO3-N losses of 0.48 m3/s and 3.77 kg/ha, respectively. For the validation period, the predicted mean monthly flow and NO3-N losses were 0.29 m3/s and 2.93 kg/ha, respectively, against measured flow and NO3-N losses of 0.18 m3/s and 1.37 kg/ha, respectively. Long-term simulations were made for a wide range of climatic conditions between 1955 and 2004 to evaluate the effects of fertilizer management practices on the NO3-N losses. A 35% reduction in NO3-N losses was observed when application rate and timing were changed from a fall application of 179.3 kg/ha to a spring application of 112 kg/ha.