22
was done in a semiarid area of Italy by Garofalo and Rinaldi (2015) for sunflower,
where small and moderate amounts of irrigation water, namely 150 and 270 mm,
respectively ensured an average seed yield, with water saving by 74 and 53%,
respectively, compared to the fully irrigated control treatment.
Wang et al. (2012) indicated that maize plants grown under alternate partial rootzone deficit irrigation in a climate controlled environmental study produced 49%
more root biomass and increased root to shoot ratio by 54%, compared to the fully
irrigated control. Similarly, in cotton, alternate partial root-zone irrigation stimulated the growth of secondary roots (Du et al. 2008). The increased secondary roots,
along with increased root to shoot ratio, are beneficial for improving water absorption (Li et al. 2013) and enhancing soil nutrient uptake (Wang et al. 2012).
Furthermore, alternate partial root-zone irrigation has been shown to increase root
activity in tomato plants by 48–59% compared to the conventional irrigation control
(Yang et al. 2012).
2.5.3 Subsurface Drip Irrigation or Infiltration Movement
Subsurface drip irrigation is the third most popular regulated deficit irrigation practice (Chai et al. 2016). It is mostly used in nursery systems and, to a lesser extent, in
the production of large scale field crops (Xu et al. 2009). Subsurface drip irrigation
has the potential to provide consistently high water use efficiency over traditional
methods, including surface drip irrigation while conserving soil, water, and energy
(Vyrlas et al. 2014). In this system, irrigation water is supplied to plants by capillary
movement from the bottom. The root-zone air space is not immediately filled with
water, in contrast with traditional irrigation where water is supplied directly overhead and fill the air space in the soil (Xu et al. 2009). Infiltration movement induces
plant hardening or internal physiological regulations caused by mild water stress
(Yactayo et al. 2013). A relatively dry soil surface under using subsurface drip irrigation permits farm equipment access and movement during the whole irrigation
period, eliminates weed growth, restricts root rot and other soil diseases and prevents crust creation (Sakellariou-Makrantonaki et al. 2000).
2.6 The Hidden Role of Intercropping Systems in Water
Saving
The aim of application of deficit irrigation is water saving and increase water use
efficiency. Similar outcome could be obtained from implementing intercropping
systems. Intercropping systems is an efficient cropping system in irrigation water
use because it produces more yields (yield of two crops) by utilizing less water
(water applied to one crop). Intercropping is found to play a crucial role in securing
S. Ouda and T. Noreldin
was done in a semiarid area of Italy by Garofalo and Rinaldi (2015) for sunflower,
where small and moderate amounts of irrigation water, namely 150 and 270 mm,
respectively ensured an average seed yield, with water saving by 74 and 53%,
respectively, compared to the fully irrigated control treatment.
Wang et al. (2012) indicated that maize plants grown under alternate partial rootzone deficit irrigation in a climate controlled environmental study produced 49%
more root biomass and increased root to shoot ratio by 54%, compared to the fully
irrigated control. Similarly, in cotton, alternate partial root-zone irrigation stimulated the growth of secondary roots (Du et al. 2008). The increased secondary roots,
along with increased root to shoot ratio, are beneficial for improving water absorption (Li et al. 2013) and enhancing soil nutrient uptake (Wang et al. 2012).
Furthermore, alternate partial root-zone irrigation has been shown to increase root
activity in tomato plants by 48–59% compared to the conventional irrigation control
(Yang et al. 2012).
2.5.3 Subsurface Drip Irrigation or Infiltration Movement
Subsurface drip irrigation is the third most popular regulated deficit irrigation practice (Chai et al. 2016). It is mostly used in nursery systems and, to a lesser extent, in
the production of large scale field crops (Xu et al. 2009). Subsurface drip irrigation
has the potential to provide consistently high water use efficiency over traditional
methods, including surface drip irrigation while conserving soil, water, and energy
(Vyrlas et al. 2014). In this system, irrigation water is supplied to plants by capillary
movement from the bottom. The root-zone air space is not immediately filled with
water, in contrast with traditional irrigation where water is supplied directly overhead and fill the air space in the soil (Xu et al. 2009). Infiltration movement induces
plant hardening or internal physiological regulations caused by mild water stress
(Yactayo et al. 2013). A relatively dry soil surface under using subsurface drip irrigation permits farm equipment access and movement during the whole irrigation
period, eliminates weed growth, restricts root rot and other soil diseases and prevents crust creation (Sakellariou-Makrantonaki et al. 2000).
2.6 The Hidden Role of Intercropping Systems in Water
Saving
The aim of application of deficit irrigation is water saving and increase water use
efficiency. Similar outcome could be obtained from implementing intercropping
systems. Intercropping systems is an efficient cropping system in irrigation water
use because it produces more yields (yield of two crops) by utilizing less water
(water applied to one crop). Intercropping is found to play a crucial role in securing
S. Ouda and T. Noreldin