Agriculture Reference
In-Depth Information
9.1 INTRODUCTION
Due to population growth, the demand on water resources increases. One option for
coping with this is to minimize the use of irrigation practices that are wasteful in
their water consumption as well as using brackish water as alternative irrigation water
resources especially in arid and semiarid areas. Egypt is considered one of the water
scarce arid countries in the Middle East. Water scarcity is forcing Egypt to use brackish
water as an alternative source for crop irrigation. The El-Salam Canal is one of the five
mega irrigation projects in Egypt and used to irrigate 2.6 billion m
2
of new reclaimed
areas in the Eastern Delta and North Sinai. Canal water is a mixture of 1.9 billion
m
3
/year of drainage water and 2.1 billion m
3
/year of fresh water from the river Nile.
Recently in Egypt, modern irrigation techniques are being called on to produce more
food with less irrigation water. Conventional deficit irrigation (CDI), considering crop
tolerance to water stress during its growing stages, is one approach that can diminish
water use without distinct yield reduction [15]. Alternate partial root irrigation (APRI)
is another water-saving irrigation technique in which irrigation amount can be reduced
without significant reduction in crop yield [16]. In this technique, approximately half
of the root system is always exposed to drying soil while the remaining half is irrigated
as in full irrigation. The wetted and dry sides of the root system are alternated with a
frequency according to soil water balance and crop water requirement [13]. Zhang et
al. [26] demonstrated that plants with two halves of their roots under alternating dry-
ing and wetting cycles developed normally with reduced stomatal opening and without
considerable leaf water deficit. Laboratory studies conducted by many researchers
[18, 26, 27, 28] manifested that stomatal regulation is managed through chemical sig-
nals from plant roots to leaves. These signals depended mainly on the development
of abscisic acid (ABA) in plant roots in the drying soil. ABA transported through the
transpiration streams and the augment of ABA concentration in plant xylem causes
closure of stomata. Thereby, the luxury transpiration was reduced without any effect
on photosynthesis [11, 22].
Many fi eld experiments have been conducted to study the behavior, yield, and wa-
ter use effi ciency of different plant species under APRI and the effectiveness of APRI
over other irrigation methods as a water-saving technique. Kang et al. [13] compared
three furrow irrigation techniques (alternate, fi xed, and conventional furrow irrigation)
for growing maize in an arid area. They concluded that root development was signifi -
cantly improved by alternate furrow irrigation. Primary root numbers, root density,
and total root dry weight were higher than in other techniques. Moreover, alternate
furrow irrigation sustained high grain yield with up to 50% reduction in the amount
of irrigation.
Kirda et al. [17] assessed the crop yield differences under CDI, APRI, and full ir-
rigation for different crops (e.g., cotton, tomato, and pepper) in a heavy clay soil under
Mediterranean climate conditions. They demonstrated that there was no signifi cant
difference in tomato yield between the APRI and full irrigation but the APRI had about
10% additional tomato yield over CDI. On the other hand, the water use effi ciency
was approximately the same in all irrigation methods in pepper crop. They also con-
cluded that no reduction in seed yield for cotton was observed with defi cit treatments
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