Irrigation of intensive olive groves in the Mediterranean environment with different water regimes on two different soils: effects on yields, water use efficiency, vegetative behaviour and water status of the crop

To cope with the FAO motto 'more food with less water' it will be important to define the irrigation strategy not only according to the variety and type of olive grove but also based on the available soil. A certain number of papers focused on assessing the effects of different water regimes on different cultivars and/or agronomical characteristics of the grove while is very difficult to find studies that try to evaluate those effects of different soils. With the aim to give a contribution in elucidate the role of the soil characteristics on water management, two experimental trials have been carried on during the same two years in olive groves with same cultivar, very similar agronomical characteristics, and climatic conditions but with quite different soils, one shallow and silty and the other deep and silty-loamy. Compared water regimes were a dry control (T0) and two irrigated with restitution of 50% (T50(WR)) and 100% (T100(WR)) of the watering volume required to restore the full crop evapotranspiration. Main results are: (i) shoot growth did not differ among water regimes; (ii) leaf water potential decreased from the T100(WR) to the T0; (iii); T50(WR) and T100(WR) showed a very significant increase of yields, particularly different in terms of drupes (much higher in the deep soil) but much more similar in terms of oil between the two soils; (iv) oil content increase in TWR respect to T0, although somewhat less on the deep soil (22.81% in average for TWR treatments and 17.32% for T0, based on two years); (v) seasonal irrigation volumes were widely different between years (72 and 800% higher in the dry year respect to the rainy year for the shallow and the deep soil, respectively) but not so different between soils in the very dry year (23% higher in the deep soil).