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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

 

This chapter in METHODS OF INTRODUCING SYSTEM MODELS INTO AGRICULTURAL RESEARCH

  1.  p. 155-176
    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

     
    Published: 2011


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doi:10.2134/advagricsystmodel2.c5

Special Features of the DayCent Modeling Package and Additional Procedures for Parameterization, Calibration, Validation, and Applications

  1. S.J. Del Grosso,
  2. W.J. Parton,
  3. C.A. Keough and
  4. M. Reyes-Fox
  1. S.J. Del Grosso (delgro@nrel.colostate.edu) and M. Reyes-Fox, USDA-ARS, Fort Collins, CO 80523; S.J. Del Grosso, W.J. Parton, and C.A. Keough, Natural Resource Ecology Lab., Colorado State Univ., Fort Collins, CO 80523.

Abstract

DayCent (Daily CENTURY) is a biogeochemical model of intermediate complexity used to simulate flows of carbon and nutrients for crop, grassland, forest, and savanna ecosystems. Required model inputs are soil texture, current and historical land use, vegetation cover, daily maximum and minimum temperature, and daily precipitation. For calibrating the model, we recommend testing model performance in the following order: soil water content, crop yield and plant growth, changes in soil organic matter levels, and N loss vectors. Different statistics should be used when evaluating model performance, including correlation coefficients, root mean square error, and mean error. For vectors that are highly variable in time (e.g., N2O emissions), the model can represent treatment impacts on seasonal emissions correctly, but not necessarily the timing at the daily scale. In addition to comparing model outputs with field observations, comparisons with alternative models are advocated to more fully evaluate model performance. Some of the most uncertain model outputs include N2, NH3, and NOx losses because these vectors are rarely measured in field experiments. Web accessible databases that include comprehensive model driver and testing data are needed to facilitate model comparisons and evaluation. DayCent has been used to simulate the impacts of climate and land use change on various crop, grassland, and forest systems around the world and is currently used to estimate soil N2O emissions from cropped and grazed lands for the annual U.S. inventory of greenhouse gases compiled by the USEPA.

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