Agriculture Reference
In-Depth Information
19.1 INTRODUCTION
Scarcity of water is one of the major factors responsible for suboptimal productivity
and decline of citrus orchards in world. Deficit irrigation (DI) is recently proposed wa-
ter saving techniques in different irrigated crops. Reducing irrigation water quantity to
optimal level of crop water requirement in particular growth stages of the crop which
is less sensitive to water deficit improves water use efficiency and quality of produces,
without affecting the yield significantly [18]. Therefore, the correct application of DI
requires the thorough understanding of the yield response of crops to irrigation [8].
As an evergreen perennial fruit crop, citrus require adequate soil water in root
zone. Irrigation water is a key input to successful cultivation of citrus especially tropi-
cal and subtropical regions of the world [20, 26]. In recent years, several research
contributions have documented the advantages of using DI in citrus. The 'Clementina
de Nules' citrus tree performance was evaluated under DI at 25% or 50% ETc dur-
ing fl owering and fruit set, initial fruit enlargement phase, and fi nal fruit growth and
maturation phases [12]. It was reported that water stress during fl owering and fruit
set period signifi cantly reduced the fruit yield up to 62% over full irrigation. It was
observed that water stress at initial fruit growth period and fi nal fruit growth period of
'Lane late' orange reduced the yield signifi cantly [23]. DI scheduled with 40 and 60%
reduction in irrigation water quantity at initial fruit enlargement stage of 'Navalina'
sweet orange in Spain did not affect the yield and fruit quality [10]. Drip irrigation at
80% crop water requirement enhanced the yield and water use effi ciency signifi cantly
in 'Nagpur' mandarin in clay soil [21]. Overall, the studies indicate that the level and
time of water stress along with its duration are the main factors responsible for success
of DI in citrus. Moreover, pedo-climatic characteristics of the orchard, crop character-
istics play a greater role in success of DI [29].
The cultivation of 'Kinnow' mandarin, a hybrid of 'King' mandarin and 'Willow
leaf' mandarin, is mainly confi ned to semiarid and arid environments of northern In-
dia, where more than 90% of annual rainfall (600 mm) is concentrated in 3 to 4 months
(June-October) of a year. Irrigation is a common practice during January-June to im-
prove the productivity of citrus orchards in this region. Ground water is the common
source of irrigation for the crop. For last few years, the shortage of irrigation water
caused by over exploitation of ground water becomes a major threat to citrus produc-
tion. Farmers are more concerned with the sustained production of 'Kinnow' mandarin
using less water. Optimal DI scheduling under drip irrigation is one of the option for
sustaining 'Kinnow' mandarin production in this region.
In absence of the information on the crop response to DI in early fruit growth
period (EFGP, April-June), the orchardists adopt faulty irrigation strategy, which af-
fects the yield drastically with inferior quality fruits. Moreover, the information on the
responses of mandarin cultivars of citrus to water stress in summer months, which co-
incides with EFEP are very limited worldwide. This chapter discusses the research re-
sults to optimize the DI scheduling in EFGP in relation to yield, fruit quality and water
use effi ciency of 'Kinnow' mandarin in a semiarid subtropical climate of North India.
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