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

Citation:  Paper number  701P0304,  . (doi: 10.13031/2013.15723)
Authors:   M. A. Youssef, R. W. Skaggs, G. M. Chescheir , and J. W. Gilliam
Keywords:   DRAINMOD-N, DRAINMOD, nitrogen models, water quality, drainage

The nitrogen simulation model, DRAINMOD-N II, was field-tested using a six-year dataset from an artificially drained site in the North Carolina Lower Coastal Plain. The test site is nearly flat with a very poorly drained sandy loam soil under natural conditions. Four experimental plots, planted to a corn-wheat-soybean rotation and managed using conventional and controlled drainage, were used in this study. Water table depth (WTD) midway between drains, drainage rates, and N concentration in drain flow were measured and meteorological data were recorded continuously. DRAINMOD-N II was calibrated for the site using the data from one plot; data sets from the other three plots were used for model testing. Simulation results showed good agreement between observed and predicted annual nitrate-nitrogen (NO3-N) leaching losses. On average, errors in predicting annual NO3-N leaching losses were 6.1, 14.3, 17, and 35.8% for the four plots. High errors in predicting annual NO3-N leaching losses were mostly induced by errors in predicting WTD and drainage rates. In spite of relatively large discrepancies on an annual basis, in some years, errors in predicting cumulative NO3-N losses over the six-year period were remarkably small. Cumulative NO3-N leaching losses over the six-year period were overpredicted by 2.7% for one plot and under-predicted by 1.5, 5.3, and 10.6% for the other three plots. Results of this study showed the potential of DRAINMOD-N II for simulating N dynamics in agroecosystems. Further research is needed to evaluate the performance of DRAINMOD-N II for different management practices and soil and climatological conditions.

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