Abstract
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.
Highlights
Morocco, located in the southern rim of the Mediterranean basin, has a semi-arid climate and observes scare and overexploited water resources [1,2]
Total rainfall during the crop cycle was 325 mm of which 130 fell in November–December 2016, coinciding with winter rest of the trees, 135 mm fell in the month of February 2017, coinciding with bud-break and 60 mm fell in August 2017, coinciding with fruit enlargement
The trial was performed for one crop cycle, it reports significant results with indicative indices as to the response of the tow clementine cultivars to different strategies of irrigation
Summary
Morocco, located in the southern rim of the Mediterranean basin, has a semi-arid climate and observes scare and overexploited water resources [1,2]. Agriculture alone consumes about 80% of water resources used in the country, and more than 90% in the Souss-Massa plain, located in the central southwestern part of the country, the main region for intensive vegetable and fruit production in the country for domestic and export markets [4,5]. The availability of surface and groundwater (GW) is very limited, due to low precipitation (less than 200 mm of rain/year) and to the low water table recharge [6,7,8]. This decrease in water yield recharge under climate change combined. Water 2020, 12, 2439 with overexploitation led to a serious quality degradation and depletion of GW, which constitutes a strategic water supply for the region [9,10,11].
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