Plant–Water Relations and Irrigation Management of Potato - The Potato: Botany, Production and Uses - page 108

Al-Kufaishi et al . (2006) used a simulation
model to calculate the amount of water required
by sugarbeets in a field experiment in Germany.
Spatially variable irrigation applied by a central
pivot system was compared to uniform irriga-
tion. The comparison revealed that loss of water
was greater for uniform applications than vari-
able rate applications (VRA). PI systems apply-
ing variable rates of irrigation (VRI) are already
available commercially. The variable irrigation
is planned according to “management zones”
defined by soil type and topography using points
collected from a GPS device. The control of VRA
(or VRI) using the actual special water status of
the crop promises a better response to the crop
needs and a better WUE. A remote thermal im-
agery system is being developed for this purpose.
Canopy temperature, measured by in-
frared thermometry, provides a non-invasive
monitoring of the water status of plants
(Cohen et al ., 2005). This system can be per-
formed automatically and provides spatial in-
formation of surface temperature. This ap-
proach enables mapping of canopy temperature
variability over large areas.
Canopy temperatures were shown to be
well related to soil water within the root zone of
cotton, as well as a stomatal conductance index
derived from canopy temperature (Padhi et al .,
2012). The relatively low spatial resolution of the
thermal images necessitated the use of high spatial
resolution of red, green, and blue (RGB) images
(Moller et al ., 2007). Zakaluk and Sri Ranjan
(2006) investigated the feasibility of using a digital
camera to determine the leaf water potential (ΨL)
of potato plants by capturing RGB digital images
in the visible region of the electromagnetic spec-
trum. Their work showed promise of using RGB
to assess leaf water potential and soil nitrate status.
The crop water stress index (CWSI) is used to nor-
malize the canopy temperature from thermal im-
ages (Tc, °C) and water status of the plants (Jones
et al ., 2002). Analysis of the ground thermal and
RGB images from three dates during each of two
growing seasons showed highly significant cor-
relations between CWSI and stomatal conduct-
ance during the tuber-bulking stage ( R 2 = 0.8-0.96,
P <0.01). Aerial thermal and RGB images revealed
significant correlation between CWSI and sto-
matal conductance ( R 2 = 0.8) (Rud et al ., 2014).
Durigon and de Jong van Lier (2013) experimen-
tally compared CWSI to the transpiration

reduction function (FRF) using common bean
grown in Brazil under full and deficit irrigation.
They found canopy temperature combined with
CWSI were as effective at predicting plant water
stress as soil-based factors like soil water pressure
head. The results presented suggest that thermal
images may serve as an efficient control tool for
variable irrigation rates and should be assessed
in potato.

7.7 Potato Responses to

Waterlogging

Abiotic stresses that are based on too much
water (flooding) or too little water (drought)
largely determine the global distribution of
plants and agricultural productivity (Visser et al .,
2003; Jackson et al ., 2009). In a flooded environ-
ment, soils rapidly become deficient in oxygen. This
condition results in the death of potato plants
due to the cessation of aerobic root respiration,
loss of water absorption, and loss of ion uptake
and transport (Visser et al ., 2003). If the flood-
ing incident is brief, for example less than a few
hours, potato plants will often survive. Never-
theless, longer-term exposure will usually result
in plant death, since potato plants have no or very
limited ability to transport oxygen from above-
ground shoots to belowground roots (Vasellati et al .,
2001). Although attempts have been made to
characterize tolerance to waterlogging in crop
plants (e.g. Dennis et al ., 2000), the development
of flood tolerance in potato has not been suc-
cessful to date.

7.8 Coping with Drought

There are currently seven cultivated potato spe-
cies and 199 wild potato species found in vari-
ous regions of the world (Hijmans and Spooner,
2001). Different wild potato species often dem-
onstrate effective adaptive responses to a wide
range of abiotic and biotic stresses.
Successful strategies for dealing with
drought stress will require breeding for
adaptation. Drought resistance traits will
need to be selected carefully (Tardieu,
2012). Incorporation of drought tolerance
into cultivated potato will involve both