Irrigation of intensive olive groves in the Mediterranean environment with different water regimes on two different soils: effects on fruit characteristics and quality parameters of the oils

Reasons of primary importance in supporting the positive trend of worldwide per capita consumption of EVOO (extra virgin olive oil), begun more than 30 years ago, are quite certainly the numerous benefits on the human health recognized in the EU by three health claims awarded by the EFSA (European Food Safety Authority). In two experimental trials carried on in intensive olive groves with quite different soils, in addition to vegetational, agronomical and physiological parameters reported in another paper, some carpological parameters and qualitative characteristics of oils have been determined and discussed in the present paper. Compared water regimes were a dry control and two irrigated with restitution, 50 and 100%, of the watering volume required to restore the full crop evapotranspiration (T_WR). Only for the deeper soil there were also an additional treatment resembling local farmers behaviour in irrigating olive (T_F); low frequency and high volumes. Results remark that: (i) the flesh:pit ratio grew passing from the dry control to the restitution of 50 and 100% but the highest value was obtained with T_F; (ii) TF, was able to modify the shape of drupes increasing their roundness, interestingly for the table olive industry; (iii) at harvest, irrigation reduced oxidative condition, mainly due to a light reduction of acidity and a significative reduction of oil oxidation indexes; (iv) under increasing seasonal irrigation volumes, the percentages of oleic acid enhanced, while that of stearic, linoleic and linolenic acids decreased; (v) it seems that water deficit conditions may increase the percentage of linolenic acid of olive oils over the maximum allowed under the EU regulations for EVOO although they have excellent quality; (vi) opposite to what was previously reported, we observed an increase of the content of total phenols in the T_WR respect to the dry control.