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Title: Simulating nitrate-nitrogen concentration from a subsurface drainage system in response to nitrogen application rates using RZWQM2

Author
item QI, ZHIMING - Colorado State University
item Ma, Liwang
item HELMERS, M - Iowa State University
item Ahuja, Lajpat
item Malone, Robert - Rob

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2011
Publication Date: 1/1/2012
Citation: Qi, Z., Ma, L., Helmers, M.J., Ahuja, L.R., Malone, R.W. 2012. Simulating nitrate-nitrogen concentration from a subsurface drainage system in response to nitrogen application rates using RZWQM2. Journal of Environmental Quality. 41(1):289-295.

Interpretive Summary: It is desirable to use a calibrated model to make recommendations without having to do field trials for all soils and weather conditions. This study demonstrated a case where a calibrated RZWQM2 model (Root Zone Water Quality Model) was used to simulate the response of NO3-N concentration in tile drainage to N application rate. The results showed that the RZWQM2 model performed “satisfactorily” in simulating the response of NO3-N concentration in tile drainage to N fertilizer rate. The simulation also identified that the N application rate required to achieving the Maximum Contamination Level (MCL) was similar to field observed data. This study consolidated the fact that the RZWQM2 model is a valid tool to predict NO3-N concentration in subsurface drainage at various N application rates, once it is calibrated for the local conditions.

Technical Abstract: Computer models have been widely used to evaluate the impact of agronomic management on nitrogen dynamics in subsurface drained field. The objective of this note was to evaluate the performance of Root Zone Water Quality Model (RZWQM2 version 2.0) in simulating the response of NO3-N concentration in tile drainage to N application rate. A 16-year field study conducted in Iowa at 9 N rates (0-252 kg N ha-1) from 1989 to 2004 was used to evaluate the model, based on previous calibration with data from 2005-2009 at this site. The results showed that the RZWQM2 model performed “satisfactorily” in simulating the response of NO3-N concentration in tile drainage to N fertilizer rate with 0.76, 0.49, and -3% for the Nash-Sutcliffe efficiency (NSE), ratio of the root mean square error to the standard deviation (RSR), and percent bias (PBIAS), respectively. The simulation also identified that the N application rate required to achieving the Maximum Contamination Level (MCL) was similar to field observed data. This study consolidated the fact that the RZWQM2 model is a valid tool to predict NO3-N concentration in subsurface drainage at various N application rates, once it is calibrated for the local condition.