Adapting the CROPGRO Perennial Forage model to predict growth and development of Pensacola bahiagrass

Abstract

Bahiagrass (Paspalum notatum Flüggé) – a warm-season perennial grass – is one of the most important forage species for livestock production in the southeastern United States. Bahiagrass pastures are often managed extensively, without the data and tools necessary for complex management. Crop simulation models have been previously developed for warm-season grasses, enabling forecast of physiological variables and evaluation of various management scenarios. The objective of this study is to calibrate the CROPGRO Perennial Forage model (CROPGRO-PFM) for bahiagrass and to evaluate the performance of the new model across six experimental datasets. Previously developed parameters for the palisadegrass (Brachiaria brizantha cv. Xaraes) model were used initially, followed by modification of parameters more predictive of bahiagrass and its differences from palisadegrass. Major changes included calibration of plant composition, cool season temperature sensitivity, and photoperiod-induced dormancy parameters, corresponding to previous observations of bahiagrass physiology. The final adapted model resulted in effective predictive accuracy for important state variables – harvested herbage mass (RMSE = 729 kg ha−1, d-index = 0.85), above-ground biomass (RMSE = 729 kg ha−1, d-index = 0.82) and crude protein concentration (RMSE = 3.1%, d-index = 0.71). Given the wide range of experimental conditions used for model development, these results suggest that the calibrated CROPGRO-PFM model will be effective for simulating physiological variables across bahiagrass pastoral systems.