A GLEAMS (ver. 2.10) model was calibrated and validated using three years (19901992) of fieldmeasured datato simulate tillage effects on nitratenitrogen (NO3N) and herbicide losses with subsurface drain tile water beneath acontinuous corn production system. The model was calibrated for chisel plow systems using 1991 field data and was validatedagainst field data of two years (1990 and 1992) for chisel plow and three years (19901992) for moldboard plow (MB), ridgetill (RT), and notill (NT) systems. The model simulations were made with a single run using data on measured tile flows;nitratenitrogen (NO3N), atrazine, and alachlor losses with tile flows; Nuptake; and other biomass parameters for theperiod 1 January 1990 through 31 December 1992 for CP, MB, RT, and NT systems. All four tillage treatments, each replicatedthree times, were applied in a randomized complete block design at Iowa State Universitys Northeastern Research Center,Nashua, Iowa, to collect field data. A specific calibration procedure for the nutrient component of the GLEAMS model wasdeveloped adjusting the Nuptake coefficient and using steadystate Npool values obtained after multiple years of the modelruns. The results of this study indicated that model simulations on subsurface drain water quality and plant parameters wereadequate for chisel plow systems and the percent difference, on the average, was <10% between predicted and measured datawith R 2 = 0.99. The change in tillage management option for MB, RT, and NT systems slightly affected the model predictionson subsurface drain water quality, probably due to the lack of a macropore option in the model and perhaps also due to nofall plowing in 1991 because of wet weather. However, calibration of the nutrient submodel using steadystate Npool valueswas successful and may be tested to simulate the longterm effects of different cropping systems on soil and water quality.