Agro-hydrological models to schedule irrigation of Mediterranean tree crops

In this paper a comparison between two agro-hydrological models, used to schedule irrigation of typicalMediterranean tree crops, is assessed. In particular the comparison between the model proposed by FAO, using a blackbox processes schematization, and the SWAP model based on the numerical analysis of Richards’ equation is initiallypresented for two irrigation seasons, 2005 and 2006, and two Mediterranean tree crops, i.e. grapevine (Vitis vinifera,L.) and olive oil (Olea europea, L.). The comparison mainly focuses on hydrological balance components and on soilwater contents.After investigating and setting the scheduling parameters ordinarily practiced by the framers in the area (i.e ordinarymanagement), the performance of the two models aimed to evaluate seasonal water requirement and irrigation time,is assessed.In the validation phase both the models satisfactorily simulated the soil water content, allowing to obtain quitecomparable values of evapotraspiration fluxes. On the other hand, when the models are used for scheduling irrigation,the FAO 56 model usually overestimates the irrigation amount, as a result of an overestimation of the transpirationfluxes. On the contrary the SWAP model simulates values of crops water requirements and a number of irrigationcorresponding to those evaluated in the ordinary scheduling at the investigated area. Finally, in order to improve theFAO 56 model performance, a modification of the stress function is presented and discussed.