Gleams model application on a heavy clay soil in Finland

The GLEAMS model version 2.10 was calibrated and validated with data from research plots on illitic clay soil near the Agricultural Research Centre at Jokioinen, Finland. Observed surface runoff, drainage flow, erosion, and associated nitrogen and phosphorus loads from 0.46 ha plots were used in the model application for a 7-year period with different management practices. Two plots were used for calibration and two plots were used for validation in the present study. The model was found to represent the soils and management with adjustment, or fine tuning, of sensitive parameters. The simulated runoff, percolation, evapotranspiration, amount of soil erosion, phosphorus (P) and nitrogen (N) losses in runoff and drainage water compared very well with observed values on the average, but differed considerably from year-to-year and especially month-to-month. Observed data were required after improved drainage installation in order to adjust parameters sensitive in water balance calculations. The P component of the model gave better estimates of the losses in runoff and with eroded soil particles than did the more complex N component. P with particulate in drainage water was simulated externally since it is a significant part of the total P lost and it is not considered in the model. Some model modifications were made to better represent the climatic conditions of Finland. The validation study indicated that GLEAMS can be used satisfactorily in Finland for comparisons of alternate management practices as recommended by the model developers.