Agriculture Reference
In-Depth Information
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Variety or species
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Growth stage
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Environment
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Salinity-stress history or sequence of salinity stress
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Rootstocks
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Soil type
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Moisture condition
8.5.1.1 Varietal Differences in Salt Tolerance
Crops differ in the ability to tolerate salinity, but if levels are high enough (> 16
dS/m), only tolerant plants will survive. Differences in varietal tolerance to salinity
and other adverse soil conditions have been known to exist for decades but it is only
in the latest decades that serious efforts have been initiated to exploit the genetic
potential of salt-tolerant crop varieties through different breeding programs. Wheat,
soybean and barley are genetically moderately tolerant ( ~EC
8 dS/m) to salin-
can produce reasonable yield at irrigation salinity of 14 dS/m (Ali and Rahman,
In recent years intensive efforts have been made at the International Rice
Research Institute at Los Banos in the Philippines to breed varieties for tolerance to
various adverse soil conditions and many advanced lines in IRRI's breeding program
show tolerance for one or more adverse soil factors. It is apparent that breeding crop
varieties tolerant to salinity offers significant opportunities for better management
of areas where salinity is a perpetual problem.
=
8.5.1.2 Growth Stage
Although some crops seem to tolerate salinity during seed germination as well
as during later growth stages, germination failures are most commonly respon-
sible for poor and spotty stands and bare spots in otherwise cultivated fields.
Frequently this is not the result of crops being especially sensitive during germi-
nation, but rather is caused by exceptionally high salt concentration in the shallow
surface zone where seeds are planted. These high salt concentrations result from
the salt that is left behind as the upward moving water is evaporated near the soil
surface.
Most plants are more sensitive to salinity during germination than at any other
growth stage. However, there are large variations in the sensitivity of germinating
seeds to salinity. Beans and sugarbeet are more sensitive to salts at germination than
are alfalfa and barley.
growth stage and showed that the tolerance pattern of barley, wheat and maize was
nearly the same as that of rice. Sugarbeet and safflower, on the other hand, were
sensitive during germination while the tolerance of soybean could either increase or
decrease between germination and maturity depending on the crop variety.
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