Effect of progressive irrigation water reductions on super-high-density olive orchards according to different scarcity scenarios

The cultivation of super-high-density (SHD) olive orchards in the Mediterranean Basin usually faces drought events due especially to low precipitation, high temperature and solar radiation in summer. Hence regulated deficit irrigation (RDI) strategies can be a useful tool for irrigation management to limit yield loss. Therefore, this work aimed to find the most suitable RDI strategy by placing special emphasis on phase II of fruit growth for SHD olive orchards irrigated below theoretical water requirements. Four irrigation strategies were defined according to different water availability scenarios: fully-irrigated, RDI1, RDI2 and RDI3, scaled to respectively supply 450, 350, 250 and 150 mm year(-1). Tree water relations, trunk growth, fruit and oil yields, were evaluated. The study was carried out for 5 years in an 'Arbequina' commercial orchard (1667 trees ha(-1)) in Villena, Alicante (Spain). The main results showed that 'Arbequina' tree irrigation water productivity (both olive and oil) gradually increased as irrigation dose lowered. Olive yield depended heavily on the applied irrigation dose, with the highest olive yield for the Control trees. However, the oil yield in the RDI1 trees was similar to that of the Control trees, but strategies RDI2 and RDI3 reduced yield. All the RDI strategies diminished vegetative development, and RDI2 was the most efficient strategy for resource distribution (olive yield vs. vegetative growth). Therefore based on oil production, vegetative growth and irrigation water savings, RDI(1 )was the most recommendable irrigation strategy for the Arbequina' olive trees cultivated in SHD under semi-arid Mediterranean conditions.