Using RZWQM-DSSAT to Simulate Drainage Water Management Across the United States Corn Belt.
Kelly Thorp, USDA-ARS-PWA-USALARC, 21881 N Cardon Ln, Maricopa, AZ 85238, Dan Jaynes, USDA-ARS, USDA-ARS-National Soil Tilth Laboratory, 2150 Pammel Dr., Ames, IA 50011-4420, and Robert Malone, USDA-ARS National Soil Tilth Laboratory, USDA-ARS, 2150 Pammel Drive, Ames, IA 50011.
Increased concentrations of nitrate-nitrogen in the surface water bodies of the Mississippi River basin have resulted from the widespread practice of subsurface drainage in agricultural systems throughout the region. Also, hypoxia in the Gulf of Mexico has been linked directly to the transport of nitrate-nitrogen down the Mississippi River from the regions of corn and soybean production in the midwestern United States. Drainage water management practices such as controlled drainage have the potential to reduce the amount of nitrate-nitrogen leaving agricultural systems through subsurface drainage; however, the performance of controlled drainage may vary across the region due to the effect of differing climatic conditions on drainage patterns. In this study, the RZWQM-DSSAT model, calibrated for a drainage site in Iowa, was used to simulate the effect of water table management under the climatic conditions of 48 different sites across the region. Simulation results were organized within a GIS to understand how the performance of controlled drainage varies across the region. Results demonstrated that controlled drainage practices were more effective at reducing nitrate-nitrogen concentrations in surface drainage throughout the southern portion of the region as compared to the northern portion.