Effect of Soil Water Availability on Yield and Some Quality Parameters of Extra Virgin Oil (Cv. Coratina)

In semi-arid regions crop yields are primarily water-limited. As reported by many authors, water supply can improve olive yield, while, on the other hand, the influence of soil water availability on olive oil quality it is not well understood. This study was conducted to determine whether soil water availability could have an effect on yield and some quality parameters of extra virgin olive oil. Trials were carried out over a three years period in an olive orchard (cv. Coratina) planted in 1992 at distances of 6 x 3 m and located in Southern Italy (Basilicata region). Yield, fruit characteristics and oil quality parameters (FFA, total phenols, alpha-tocopherol content, peroxide value, K232, K270) for rainfed plants were compared with those observed for irrigated trees, taking into account only the on years (6th and 8th year after planting). In the irrigated treatment seasonal water supply ranged from 128 to 203 mm, according to the climatic variables (rainfall and crop evapotranspiration). Soil water potential in the non-irrigated plot was never above the permanent wilting point for olive tree (-2,5 MPa). Olive yield was statistically different in the 6th year after planting between treatments (irrigated and non-irrigated) while, in the 8th year, no difference was observed, probably because of a sort of recovering by the rainfed plants after the non-bearing year (7th year after planting). For the productions obtained in the 8th year after planting, soil water availability did not seem to affect fruit dry weight and oil quality parameters, while slight different results could be observed for the productions of the 6th year after planting. However, this latter result could be attributed to the different plant crop load and fruit ripening pattern.