The FAO field-crop model AquaCrop for maize was calibrated using data sets from Davis, California. The parameters obtained were then used to test AquaCrop against three years of maize data set from Bushland, Texas. The Bushland results showed a slightly higher simulated biomass and simulated canopy cover during very early in the season. The over estimation was probably due to the incorrect emergence date. In the model, emergence date is when most seedlings have emerged, while many may consider emergence as the time when a significant fraction of the seedling came out. Delayed emergence in the Bushland data sets could also come in the form of unfavorable weather conditions, as it was reported in one data set (1989), whereby hail occurred ten days after emergence beat the above-ground plants to ground level for that season. When emergence date was adjusted, the biomass production, canopy cover and crop evapotranspiration were reasonably well simulated. The simulation shows the importance of knowing more exactly when emergence is in the simulation and also the timing of senescence.