Capra A and Mannino R
Climate characteristics play an essential role in the crop evapotranspiration and therefore affect irrigation. Reference evapotranspiration (ET0) is a climatic parameter that can be computed from weather data and used to a reliable variable for assessing long-term trends of the atmospheric evaporative demand. The study aims to evaluate the effects of the climate change on ET0 and citrus and tomato irrigation scheduling parameters (irrigation depth, length of the irrigation season and number of irrigation) in Calabria, a Region of South Italy. The study covered 89 years (1925-2013) and 9 of the most relevant irrigated areas in the Region. The software CROPWAT was used to estimate the irrigation scheduling parameters. The time series were analyzed at yearly and seasonal scale using standard trend analysis tests (Mann-Kendall and linear trend test). The results showed a slight decreasing trend for maximum temperature and both increasing and decreasing trends for minimum temperature. Due to the asymmetric behavior of temperatures, impact on ET0 resulted in a decreasing tendency (-5.51 mm.decade-1). There was a slight decrease in the seasonal irrigation depth for both citrus and tomato. The average annual magnitude of decreases throughout Calabria were 2.40 and 5.51 mm.decade-1 for citrus and tomato, respectively, corresponding to -7% and -11% of the mean irrigation depth of the period considered. This trend depended on both the decreased ET0 and precipitation trend: precipitation decreased at yearly scale, but increased in summer, the season when irrigation requirements are higher in the environment considered. The positive trend in summer precipitation also caused an advance of the last watering, resulting in a slight decrease of the length of the irrigation season. The results, on the whole, showed the importance of studies at regional scale considering the detection of trends even opposite with respect to those founded in studies on other areas in the same Mediterranean region. The elaboration of more local studies is useful in order to deepen knowledge on the problematic of each zone and to plan concrete actions.
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