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FIELD TESTING OF DRAINMOD-N

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

Citation:  Transactions of the ASAE. 40(4): 1077-1085. (doi: 10.13031/2013.21360) @1997
Authors:   M. A. Brevé, R. W. Skaggs, J. W. Gilliam, J. E. Parsons, A. T. Mohammad, G. M. Chescheir, R. O. Evans
Keywords:   Subsurface drainage, Water quality, Drainmod, Controlled drainage, Subirrigation, Nitrogen loss

This study was conducted to evaluate the performance of DRAINMOD-N, a nitrogen fate and transport model for artificially drained soils, based on a comparison between predicted and observed hydrologic and nitrogen variables for an experimental site in eastern North Carolina. The site consisted of six plots drained by subsurface drain tubes 1.25 m deep and 23 m apart. Each plot was instrumented to measure water table depth, subsurface drainage, surface runoff and subirrigation rates. There were two replications of three water management treatments: conventional drainage, controlled drainage and subirrigation. Crops were winter wheat followed by soybean. Results showed the model did a good job in describing the hydrology of the site. On average the predicted daily water table depths were within 0.13 m of observed during the 14-month study period. Differences between predicted and observed cumulative subsurface drainage and surface runoff volumes were less than 0.10 and 0.09 m, respectively, for all treatments. Predictions for the movement and fate of nitrogen were also in good agreement with measured results. Simulated nitratenitrogen (NO3-N) losses in subsurface drainage water were within 1.5 kg/ha of the observed values for the 14-month period. Differences between simulated and observed total NO3-N losses (subsurface drainage plus surface runoff) were within 3.0 kg/ha.

Results of this study indicated DRAINMOD-N could be used to simulate nitrogen losses in poorly drained soils with artificial drainage. The model, however, needs to be tested for longer periods of time and under different climatic conditions and soil types, before it can be recommended for general use.

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