Monday, November 5, 2007 - 10:10 AM
33-3
AquaCrop – Model Parameterization and Testing for Maize.
The first crop chosen for parameterization and testing of the FAO AquaCrop model is maize. Several data sets on field maize collected at Davis, California were selected to do the preliminary parameterization. The model with these tentative parameters was then used to simulate the productivity of maize, of the same or different cultivars, grown also at Davis but in some other years. The parameters were then adjusted and finalized by comparing the simulation outputs with measured data. Here we report the values of the parameters and the testing of the calibrated model using data from maize experiments at Davis conducted over several decades. The emphasis is on irrigation and water regimes. The testing of the calibrated model with historical maize data collected at Bushland , Texas and other locations is reported by Heng et al. in this session. The parameterized AquaCrop maize requires as input only daily weather data, plant density, emergence date, cultivar season length, maximum effective rooting depth, upper and lower limits of soil water storage capacity, soil moisture at planting, irrigation schedule, and the general level of mineral nutrients, particularly nitrogen. Output includes the daily time course of canopy development and senescence, of canopy transpiration, of biomass accumulation, of biomass in the yield component, and of soil water balance. The results of the testing are shown as these time courses, plotted along with the measured data. As expected, the model performs better in the estimation of potential productivity of maize when water and nutrients are not limiting. For situations where the crop experiences water stress at least during a part of its life cycle, the model still does reasonably well but the estimated productivity is more prone to deviate from the measured. Possible reasons for the deviations are discussed along with the results of sensitivity analyses.
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