Agriculture Reference
In-Depth Information
of the area (ET-100%). The data presented here
suggest the crop may have been over-irrigated in
some cases, and employing soil-moisture sensors
at the root zone may be useful for water saving.
Studies of deficit irrigation (DI) under field
conditions have become increasingly important
in areas that rely heavily on fresh water supply.
In Oregon, USA, Shock and Feibert (2002) stud-
ied three DI treatments. At each irrigation
application,
100,
70,
and 50% of the accumu-
lated evapotranspiration (ETc) was applied. Over
3
years, the potato crop lost total yield and
grade under DI, with reduced profitability. Alva
(2008) working in Prosser, Washington, USA,
with cultivar Ranger Russet obtained similar
results. These results demonstrated that DI for
potato growing in the semi-arid environment of
western USA was not economically viable. Stark
et al
. (2013) working in Aberdeen, Idaho, found
that the greatest reduction in total yield and in US
No
1
yield occurred when potatoes were irrigated
at 70% ET until the beginning of late bulking,
when irrigation was terminated. They also re-
ported a differential response to drought among
the six cultivars included in their experiments.
Geerts and Raes (2009) discussed DI as a
strategy to maximize crop water productivity in
dry areas. They state that no single DI strategy
applies to all crops, the levels of tolerance to
drought differ among crops, at the various stages
of plant development for each crop. Hence, sched-
uling irrigation for the period from tuber initi-
ation through mid-bulking, and selecting culti-
vars that use less water and/or are less sensitive
to water stress, are recommended.
Fabeiro
et al
. (2001), working in a semi-arid
climate in Spain, also studied DI in potato and
found tuber yield was correlated with the
amount of water applied. The most adverse effect
on yield occurred when water shortage was im-
posed during the bulking and maturation stages.
However, Darwish
et al
. (2006) did not observe
reduced tuber yield of potato cultivar Santana
under DI in Lebanon using 80% of measured
evapotranspiration compared to the control of
100%. Similarly, Nimah and Bashour (2010) found
that irrigating
50-
75% of the root zone of potato
and pepper gave better yield than the control in a
study of potato cultivar Spunta and pepper culti-
var Andalus in Lebanon. Water saving of up to
195 mm for potato and 192 mm for pepper was
obtained, without reduction in total yield for
both crops, by limiting water penetration to the
top 50% of the root zone.
Partial root zone drying (PRD) is a modified
form of deficit irrigation. This procedure involves
wetting only one part of the root zone in each
irrigation event, letting the other part of the root
zone dry, and then rewetting it by shifting water
application to the dry side and letting the other
side dry. Xie
et al
. (2012), working in a semi-arid
climate in northern China, found that reducing
irrigation to 50% of the control did not affect
tuber yield, whereas WUE was increased sig-
nificantly, regardless of the irrigation method.
A partial root zone drying (PRD50) irrigation
procedure, where furrows were alternately
watered and dried in each irrigation cycle, gave
the best results. Yield differences among cultivars
and locations were indicative of a genotype-
environment (G × E) interaction. These interactions
probably explain the conflicting data and suggest
DI needs to be assessed under local climatic
and management conditions.
Muñoz-Carpena
et al
. (2005) found that irri-
gating tomato with a low-volume/high-frequency
(LVHF) soil moisture-based drip irrigation on
shallow sandy soil reduced water use while not
significantly affecting tomato yield. Tensiometers
at the -
15
kPa setpoint resulted in 73% reduction
in water use compared to a control irrigation treat-
ment, or 50% with respect to the historical evapo-
transpiration demand of the area (ET-100%).
These authors reported the development of an
inexpensive irrigation controller that reduced water
use up to 61% compared to evapotranspiration-
based application and up to 79% when using
switching tensiometers. Additional studies are
needed to investigate opportunities to conserve
water using DI and PRD under different growing
conditions and with different potato cultivars.
Precision irrigation
Precision irrigation (PI) is defined as timely and
accurate water application in accordance with
spatial and temporal soil properties in response
to plant requirements during different growth
stages (Al-Kufaishi
et al
., 2006). PI is an import-
ant component of the precision agriculture (PA)
concept that aims at increased farming efficiency
and profitability and enhances environmental
sustainability.
