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Book: Methods of Introducing System Models into Agricultural Research
Published by: American Society of Agronomy, Crop Science Society of America, Soil Science Society of America



  1.  p. 95-115
    Advances in Agricultural Systems Modeling 2.
    Methods of Introducing System Models into Agricultural Research

    Laj R. Ahuja and Liwang Ma (ed.)

    ISBN: 978-0-89118-196-5


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Parameterizing LEACHM Model for Simulating Water Drainage Fluxes and Nitrate Leaching Losses

  1. Jay D. Jabro,
  2. John L. Hutson and
  3. Ann D. Jabro
  1. J.D. Jabro (jay.jabro@ars.usda.gov), USDA-ARS, Northern Plains Agricultural Research Lab., 1500 N. Central Ave., Sidney, MT 59270; J.L. Hutson, School of the Environment, Flinders Univ., Adelaide 5001, Australia; A.D. Jabro, School of Communications and Information Systems, Robert Morris Univ., Moon Township, PA 15108.


Model calibration, validation, and sensitivity analysis are essential processes in the application and evaluation of computer simulation models. The utility of a model requires consideration of parameter selection, sensitivity analysis, calibration, and validation, but the extent to which each of these aspects is pursued depends on the reasons for model use. This chapter discusses calibration, validation, and sensitivity analysis for the LEACHM model and an example of its performance using field measured annual water drainage fluxes and NO3–N leaching losses under a continuous corn (Zea mays L.) cropping system. LEACHM calibration was performed to optimize the match between simulated and measured field data collected from control, fertilized, and manure treatments. The model was calibrated to the field site conditions using 1989–1990 data from a long-term leaching experiment conducted on a Hagerstown silt loam soil. The initial stage of calibration focused on small changes to soil water flow parameters in the model. The second phase, calibration, focused on input parameters controlling soil N transformation processes and rate constants in the model. After the calibration process was completed, the model was validated using 1988–1989, 1990–1991, 1991–1992, and 1992–1993 data by comparing model simulations with field measured data. Sensitivity analyses were performed on the calibrated LEACHM model by changing the values of input parameters within acceptable ranges. The LEACHM model was slightly sensitive to most input parameters; however, it was very sensitive to denitrification rates, initial soil water potential/water content, and the b parameter in the Campbell equation.

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