Adapting the CROPGRO Model to Predict Growth of Tropical Forage Grasses.

Warm-season grasses have high economic importance for cattle production in tropical regions and tools to aid in management and research of these forages would be highly beneficial. Crop simulation models have the ability to synthesize many physiological processes and have the potential to be important research and production tools.  Panicum maximum is widely used in Brazil. Its high yield potential has been well documented in the literature, with herbage production between 18 and 34 Mg DM ha^-1.  It can also become an important  bioenegy crop. The objective of this research was to adapt the perennial CROPGRO Forage model to simulate growth of the tropical species guineagrass [Panicum maximum. Jacq cv. Tanzania] and to describe model adaptation for this species.  In order to develop the CROPGRO parameters for this species, we used values and relationships reported from literature and calibrated other parameters and relationships by comparison to observed growth, development, dry matter accumulation and partitioning based on a field experiment conducted in 2003 and 2004 in Piracicaba, SP, Brazil. Species parameters were improved, and after these changes leaf area index, partitioning and biomass accumulation were better simulated. The results of the adaptation suggest that the CROPGRO Model is an efficient tool and can be used to simulate growth of Tanzania guineagrass.