Simulating the Dynamics of Photosynthesis and Regrowth of Tifton 85 Bermudagrass using the CROPGRO-Forage Model.

The CROPGRO model is a process-based model of crop growth.  It simulates general biological processes such as photosynthesis and nitrogen (N) uptake using parameters unique to each species in order to predict crop growth under a variety of conditions.  These species parameters are separate from the model itself making CROPGRO a versatile model adaptable to new species upon estimating values for these parameters.  CROPGRO-Forage is a modified version of CROPGRO that was developed to better model the growth of tropical perennial grasses.  This version was adapted for bahiagrass (Paspalum notatum Flugge.), but previously no set of species parameters for bermudagrass (Cynodon dactylon L. Pers.) had been estimated.  This project involved the calibration and validation of values for species parameters affecting photosynthesis and dry matter partitioning based on a field experiment conducted in 2006 and 2007 near Gainesville, FL.  Data from weekly canopy photosynthesis, leaf mass, stem mass, and rhizome mass measurements were used.  Data collected from the highest and lowest N treatments were used for calibration of the parameters and data from the middle two N treatments were used for validation of the parameter values.  The generalized likelihood uncertainty estimation (GLUE) approach was used for parameter estimation while RMSE and Wilmott agreement index were used as criteria for model validation.