Adaptation to climate change of irrigation management of Peach tree cultivars

It is a common irrigation practice of fruit growers to fine-tune timing and amount ofwater gifts to achieve higher productivity and better quality. This requires differentirrigation strategies during different phenological stages. Moreover, irrigationmanagement should be adapted to different cultivars, besides weather and climate.Finally, after harvest, water gifts may be reduced to the minimum level required forplant survival. Adaptation to climate change adds an additional dimension to thechallenge of designing and applying optimal irrigation scheduling.This challenge can be met by a combination of experiments and modelling on the waterbalance of the soil plant atmosphere system. The objective of this paper is to evaluatethe magnitude and significance of differences in the modelled soil water deficit (as afunction of time) when taking into account the specific phenological cycle of eachcultivar versus a generic assessment for each species.We present the results of a case study on Peach cultivars in an area of the Po Valleywhere fruit crops are intensively grown (Imola). We evaluated for several Peachcultivars the soil water deficit and the irrigation requirement taking into account theshifting in phenological phases in response to air temperature. This analysis isperformed taking into account the variability of soils.A reference (1961-90) and future (2021-2050) climate were considered. Referenceclimate has been produced applying a spatial statistic approach on groundobservations. Future climate scenario has been generated from statistical downscalingof general circulation models (AOGCM). The results consist of daily time series ofmaximum and minimum temperature, and daily rainfall on a 35km*35km grid. The gridnode located near Ravenna is the most representative of the local climate within thestudy area.The phenological development in reference and future climate is modeled using phase- specific thermal times and variety specific thermal requirements for peach cultivars.These requirements were estimated using phenological observations over severalyears in Emilia Romagna region and scientific literature. We calculated the dates ofstart and end of rest completion, flowering, fruit development and ripening stages, fromlate autumn through late summer.Then, a mechanistic model of water flow in the soil-plant-atmosphere continuum wasused to describe the hydrological conditions in each phenological phase in response toclimate and irrigation. Crop-specific input data and model parameters were estimatedon the basis of local experiments and of scientific literature and assumed to begenerically representative of the specie. Soils hydrological properties of the study areawere determined from HYPRES pedo-transfer functions. Upper boundary conditionswere derived from the two climate scenarios.Statistics on time series of soil water deficit were compared with control numericalexperiments where both inter-cultivars differences and the shifting of phenologicalstages were neglected.