ICARDA annual report 2004

ICARDA Annual Report 2004
44
In summary, the results showed
that supplemental irrigation is a
viable way of increasing and stabilizing
food legume yields. It can
also boost water productivity
(water-use efficiency), allowing
farmers to irrigate more land and
produce more crops. Sowing coolseason
legumes early increases
yields and, when combined with
supplemental irrigation, can help
crops escape terminal drought
stress.
Irrigation in rainfed areas, however,
comes at a cost. Economic and
feasibility studies are needed to
assess how farmers can best allocate
their limited water supplies
among different legume and cereal
crops. In this study, food legumes
produced around 0.5 kg grain per
cubic meter of water added
through SI. This response to SI is
only half of that obtained for cereal
crops in the same location. The
gross economic return per unit of
water consumed under SI is also
one-third higher in wheat than in
legumes.
However, the economic return
per kilogram of legumes is greater
than that of cereals, and legumes
also increase the nitrogen and
organic matter content of the soil.
So, when legumes are used in rotation
with cereals, they improve soil
structure, and increase both the
sustainability of the system and the
fertilizer-use efficiency of the cereal
crops. All these factors, plus environmental
conditions, production
costs and crop prices, need to be
taken into account, when weighing
up the costs and benefits of irrigating
different crops.
Response of ICARDA’s
drought-tolerant varieties
of food legumes to salinity
Salinity affects about 10 to 30% of
the cultivated lands in WANA
countries. Farmers in these saltaffected
areas have fewer choices of
crops to grow since many species,
especially food legumes, are sensitive
to salinity. Most breeding
efforts have focused on finding tolerance
to drought and little has
been done to characterize or
improve tolerance to salinity.
In 1998, international
researchers from INRA,France;
University of Wageningen, the
Netherlands; ISA,Italy;
CIHEAM/IAMB; and ICARDA
developed a research program to
study the tolerance of cereals and
legumes to salinity. The goal was to
verify whether there is a relationship
between tolerance to drought
and tolerance to salinity, and identify
parameters to improve crop tolerance
to salinity. The studies were
conducted on varieties developed
by ICARDA for drought tolerance,
using greenhouses and lysimeters
at CIHEAM-IAMB, Italy. So far,
results have been obtained for
legumes and the work on cereals is
continuing.
The chickpea and faba bean
results are particularly impressive.
Researchers found that varieties
that were sensitive to drought were
more tolerant of saline conditions,
rather than drought-tolerant varieties.
The drought-tolerant varieties
had adopted a classical response to
salinity - the plant shortened its
growing period by reducing its use
of water while maintaining a high
water potential. This strategy has a
cost of lower water-use efficiency
under saline conditions. However,
the legume varieties that are sensitive
to drought were able to slow
down foliar senescence. By producing
new leaves and new reproductive
organs, as well as accumulating
vegetated biomass during the last
phase of vegetative growth, these
drought-senstive plants had a net
improvement in water-use efficiency
compared to tolerant varieties.
The studies indicate that, for
rainfed legumes, the mechanisms
governing tolerance to drought and
salinity are different, as is the case
with many field crops such as
maize and wheat. Therefore, the
elimination of winter legumes from
the rotation is not advised. The
choice of the appropriate variety,
depending on salinity level and
species, permits a substantial
increase of grain yield which
approaches yields obtained in soils
that are not affected by salinity.
Lysimeters installed at
CIHEAM-Bari, Italy to
study lentil crop response
to various levels of
salinity.