Assessing irrigated crops' adaptability under future climate: the interplay of water management and cultivars' responses

A case-study is presented on an irrigated district in Southern Italy ("Destra Sele", Campania Region). Two climate cases were considered: reference (1961-90) and future (2021-2050) climate, the former from climatic statistics, and the latter from statistical downscaling of predictions by general circulation models (AOGCM). ) Department of Geoscience and Remote Sensing, Delft University of Technology, Delft, The Netherlands The soil water balance was simulated, in the reference and future climate, by means of a mechanistic model of water flow in the soil-plant-atmosphere system (SWAP). Twenty three soil units were identified in the "Destra Sele" district and their hydrological properties were determined. Simulations were performed both with optimal water availability and under constraints that irrigation schemes may pose, thus different deficit irrigation strategies were simulated. Indicators of the soil water regime were computed from simulation output and the marginal increase of transpiration per unit of irrigation volume (IP = ?Tact/Ir, where IP is a measure of irrigation performance) was determined. For several maize and tomato cultivars, hydrologic requirements were determined by means of yield response functions to water availability, through the re-analysis of experimental data derived from local experiments and scientific literature. In all soil units, water availability indicators were determined, for the reference and future climate case and for different irrigation scheduling options, then evaluated against cultivars' hydrologic requirements. This led to maps of locations where each cultivar is expected to be compatible with climate. Less water intensive cultivars and irrigation schedules that optimize transpiration (and yield) could be identified. The case study has shown how, in the future climate scenario, with limited water resources, the intra-specific biodiversity of crops will allow to maintain the current production system.