Response of Clementine Mandarin to Water-Saving Strategies under Water Scarcity Conditions

Water scarcity is the most constraining factor for crop production, especially in arid and semi-arid areas of Mediterranean countries such as Morocco. Within these conditions, different water-saving strategies using deficit irrigation (DI) were tested on two six-years old clementine varieties ('Sidi Aissa' and 'Orogrande'). These DI strategies were applied during the second part of fruit growth and during fruit maturation and included: the control treatment (Cntl), in which the trees received 100% of crop evapotranspiration (ETc) for the entire irrigation season; regulated deficit irrigation (RDI), with an application of 75% of ETc (RDI-1); partial rootzone drying (PRD), with an alternating irrigation between the two root system halves for 3-4 (PRD-3/4) and 7 (PRD-7) days, with an application of 50% crop water requirements; and RDI-2, with an application of 50% of crop water needs during fruit maturation. The results indicate that the trees preferably absorb the water from the upper 0-30 cm-depth soil profile and that fruit drop was increased by PRD for 'Sidi Aissa', whereas RDI-1 had no effect on this parameter. The DI strategies had no effect on fruit drop for 'Orogrande'. The PRD reduced fruit size, yield and fruit juice content, with the effect being more pronounced on 'Sidi Aissa'. The RDI-1 had no effect on fruit yield for 'Orogrande' but reduced it for 'Sidi Aissa'. RDI-2 had no effect on yield, fruit size or fruit juice content. The DIs tested increased water use efficiency and enhanced fruit maturation as a result of increased juice sugar content and reduced acidity. The PRD tends to increase salt accumulation in the rootzone. Overall, 'Orogrande' was less sensitive to water stress and was more water-use efficient, and, under the semi-arid conditions of the experimental zone, PRD should not be used on clementine.