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 of water gifts to achieve higher productivity and better quality of Peach cultivars. This requires different irrigation strategies during different phenological stages. Moreover, irrigation management should be adapted to different cultivars, besides weather and climate. Finally, after harvest, water gifts may be reduced to the minimum level required for plant survival. Adaptation to climate change adds an additional dimension to the challenge of designing and applying optimal irrigation scheduling.This challenge can be met by a combination of experiments and modelling on the water balance of the soil plant atmosphere system. The objective of this paper is to evaluate the magnitude and significance of differences in the modelled soil water deficit and in the resulting irrigation water gifts (as a function of time) when taking into account the specific phenological cycle of each cultivar versus a generic assessment for each species.We present the results of a case study on Peach cultivars in an area of the Po Valley where fruit crops are intensively grown. We evaluated for three Peach cultivars the soil water deficit and the irrigation requirement taking into account the shifting in phenological phases in response to air temperature. This analysis is performed taking into account the variability of soils.A reference (1961-90) and future (2021-2050) climate were considered. The reference climate data set has been produced applying a spatial statistic approach on ground observations. The future climate data set has been generated from statistical downscaling of predictions by general circulation models (AOGCM). The data sets consist of daily time series of maximum and minimum temperature, and daily rainfall on a 35 km × 35 km grid. The grid node located near Ravenna is the most representative of the local climate within the study area.The phenological development in the reference and future climate is modelled using phase - specific thermal times and specific thermal requirements for each peach cultivar. These requirements were estimated using phenological observations over several years in the Emilia Romagna region and scientific literature. We calculated the dates of start and end of rest completion, flowering, fruit development and ripening stages, from late autumn through late summer.Then, a mechanistic model of water flow in the soil-plant-atmosphere continuum was used to describe the hydrological conditions in each phenological phase in response to climate and irrigation. Species-specific input data and model parameters were estimated on the basis of local experiments and of scientific literature and assumed to be generically representative of the species. Soils' hydrological properties of the study area were determined from soil texture using the HYPRES pedo-transfer functions. Upper boundary conditions were derived from the two climate scenarios.Despite the high evaporative demand and summer water shortage predicted for future climate scenario the impact on peach cultivars is positive since phenological stages from flowering to ripening are placed in rainy periods. Inter-cultivars differences have been assessed for future climate scenario concerning the required irrigation volumes in both optimal and in Regulated Deficit Irrigation managements.