AquaCrop Model Calibration and Validation for Processing Tomato Crop in a Sub-Humid Climate

The FAO model AquaCrop has been calibrated using historical datasets from irrigation experiments carried out from 2004 to 2012 in the Po Valley (northern Italy) sub-humid climate. Calibrated parameters have been then validated on eight independent datasets collected in a period of time ranging from 2004 to 2010. The model has been validated for the following outputs: soil-water content, total yield, harvest index, total biomass and its partition in above ground vegetation and fruit. The objective was to analyze the performance of AquaCrop under different irrigation strategies affecting the plant water status during the crop cycles and the final productivity. AquaCrop model adequately simulated processing tomato yield but it was less precise predicting harvest index and biomass growth in phenological stages other than plant maturity. Soil volumetric water content prediction was difficult to calibrate. The model seems not able to react to particular soil hydraulic conditions, like significant capillary rise from shallow water table, or accumulating errors originated by poor prediction of crop ET with deficit irrigation management. Nevertheless, getting close to harvest and in dry years, predicted values are matching better observed soil volumetric water content. In order to calibrate AquaCrop for the local condition some of the conservative parameters needed to be modified. AquaCrop, although not designed to be used to manage crop irrigation at daily step, shows the potentiality to be adapted or modified that respect.