ABSTRACT
The agricultural sector is a major consumer of water and produces more than 40% of the annual global food production by 70% of all freshwater withdrawals (Food and Organization, 2008). As drought becomes a great concern all around the world, improving the efficiency of water resources used in the agricultural sector is a priority for enhanced food security. It is suggested that food demand will increase 50% by 2030 as the world population grows beyond 7.5 billion (Winfield, 2012). A major challenge for agriculture is to provide the world’s growing population with a sustainable and secure supply of safe and sufficient food that meets food preferences for an active and healthy life. Drought and flooding caused by climate change is a great threat to the sustainability of water resources and directly affect global economies, local agriculture, and the environment (Gutiérrez et al., 2014). No single definition exists for drought; however, the prevailing definition of drought is defined as low moisture conditions over a period of time (McDaniel et al., 2017). Drought is considered as the main constraint on the extension of cultivated lands and the increase of crop production in many parts of the world (Dubois, 2011). Therefore, in a scenario of population growth, climate change, and global water scarcity, a more efficient management of the water resources is a must to conserve water as much as possible and assure crop production (Raza et al., 2012). Deficit irrigation (DI) is a strategy for farmers facing water availability challenges. It allows a crop to tolerate some degree of water deficit to reduce cost and potentially increase net income where water supplies are limited, or water costs are high (Kirda et al., 1999). In this irrigation strategy, the amount of applied water is kept below the actual irrigation requirement, and slight stress that is developed has a minimal effect on yield. It may range from moderate to extremely severe (Heng, 2002). The physiological responses of plants to water stress and their relative importance for crop productivity vary with species, cultivars, soil type, nutrients, and climate (Akıncı and Lösel, 2012; Forni et al., 2017). Some crops are relatively resistant to water stress, or they use some strategies to cope with the soil moisture limitations (López-López et al., 2018). They may avoid stress by deep rooting, allowing access to soil moisture lower in the soil profile (Chaves et al., 2002; Lisar et al., 2012). DI can lead to many advantageous if it is properly applied (Galindo et al., 2018). An improvement of fruit quality was found in several studies with little or no yield decline (George and Nissen, 1992; Gheysari et al., 2017; Patanè et al., 2011; Yang et al., 2017); however, an undesirable yield penalty was reported in some studies in parallel with improvement of water use efficiency (WUE) and quality of some crops (Chen et al., 2013; She et al., 2018; Zhang et al., 2017; Zheng et al., 2013). The decline in water availability for irrigation and the positive results obtained by DI in some fruit 682crops have improved the interest in developing information on DI for a variety of crops (Chai et al., 2016; Consoli et al., 2017; Yang et al., 2017).
