Evaluation of CSM-Cropgro-Cotton for Simulating Cotton Growth Responses to Irrigation, Nitrogen Fertilizer, Planting Density, and Free-Air Carbon Dioxide Enrichment in Central Arizona

CROPGRO is a crop growth simulation algorithm within the Cropping System Model (CSM), as distributed with the Decision Support System for Agrotechnology Transfer (DSSAT).  Originally developed for simulating soybean growth and development, CROPGRO was recently re-parameterized for cotton, but further evaluation is necessary to demonstrate the model's performance for cotton production systems.  Our objective was to evaluate CSM-CROPGRO-Cotton using data from three historic cotton experiments conducted at the Maricopa Agricultural Center in Maricopa, Arizona.  The first field experiment tested ambient atmospheric carbon dioxide (CO₂) versus free-air CO₂ enrichment (FACE)  for two irrigation levels over two growing seasons (1990 and 1991).  Treatments for the second field experiment included two irrigation levels and two nitrogen fertilization levels for one growing season (1999).  The third field experiment tested three planting densities and two nitrogen fertilization rates with optimum irrigation for two growing seasons (2002 and 2003).  CROPGRO-Cotton was parameterized to simulate the experimental conditions of each growing season separately.  Model simulations of emergence date, anthesis date, leaf area index, canopy weight, canopy height, canopy width, seed yield, and evapotranspiration were compared to field observations. The model was generally able to simulate cotton growth and development responses to irrigation; however, the CSM evapotranspiration routines required modification to appropriately simulate the arid conditions of the field location.  Model responses to nitrogen fertilization were highly dependent on initial soil nutrient contents, which were not available in some growing seasons.  The model tended to overestimate crop growth responses for dense plant stands.  Model responses to CO₂ are forthcoming.  If sufficient information is available to specify key model parameters, CROPGRO-Cotton can reasonably simulate crop growth and development responses for typical cotton production systems in arid regions.