GLEAMS-SWT WITH NUTRIENTS

This article introduces the Groundwater Loading Effects of Agricultural Management Systems with Subsurface drainage and Water Table (GLEAMS-SWT) with nutrients model. This version contains GLEAMS' nutrient component and additional routines to predict nitrogen loss from subsurface drainage. Comparisons of GLEAMS-SWT and GLEAMS nitrogen and phosphorus loss predictions with six years of measured nitrogen and phosphorus losses from nonsubsurface and subsurface drained plots located at Ben Hur Research Farm in Baton Rouge, Louisiana, showed that: (1) GLEAMS-SWT overpredicted total (ammonia and nitrate both in solution and solids) surface nitrogen (TSN) loss by 10%, and GLEAMS underpredicted TSN loss by 38% for the nonsubsurface drained plot; (2) GLEAMS-SWT overpredicted TSN loss by 31%, and GLEAMS overpredicted it by 7% for the subsurface drained plot; (3) both models severely underpredicted total (solution and solids) surface phosphorus losses for the nonsubsurface and subsurface drained plots; and (4) GLEAMS-SWT overpredicted total nitrogen loss in subsurface drainage nearly 7-fold.