Characterization of Evapotranspiration and effective precipitation in the Olive Areas of Extremadura, Spain. (1990-2021)

The olive tree (Olea europaea L.) is one of the main woody perennial crops in Europe, especially in the Mediterranean area. The area dedicated to olive cultivation in the European Union (EU) has increased in the last decade, reaching 4.6 million hectares. Extremadura (Spain) is the region with a semi-arid Mediterranean climate located most south-west of Europe. It has a great climatological contrast in the North-South direction. Numerous studies indicate that an increase in temperatures and a reduction in precipitation is expected due to climate change in the Mediterranean region. This would cause an increase in crop Evapotranspiration and a lower contribution of rain, especially in dryland crops. Using time series of climate data (1990-2021), the differences between areas have been analyzed using an Anova and Tukey test. The trend of Evapotranspiration of the olive crop and annual effective Precipitation  in 13 olive-growing regions of Extremadura was also analyzed. To determine the monotonic trend, the Mann-Kendal test and Sen's slope estimator were used. The results showed clear differences between the olive-growing areas, for the analyzed indices. An increase in Evapotranspiration was found in important Olive-growing areas. However, the effective precipitation did not show any trend. These results contribute to the climatic characterization of the Olive-growing regions of Extremadura and could affect the yields and quality of production, requiring a varietal adaptation and cultivation techniques, as well as a change in the distribution of suitable cultivation areas.

Keywords: Olive tree, Agroclimatology, Evapotranspiration, Extremadura