Management of Salt-Affected Soils - Practices of Irrigation and On-farm Water Management - page 297

8.5.1.3 Environmental Factors
Climatic conditions greatly influence plant responses to salinity. Normally, the crop
species show greater tolerance to salinity at the location where the environment is
cold and humid than at the location where the environment is hot and dry. In some
parts of India, rice is grown during both the rainy season (kharif) and the dry season
(rabi). The yield reduction with increasing salinity is much more in the dry than
in the wet season. This is because the dry climate accelerates evaporation, which
accumulates salts at the surface. In addition, the higher transpiration loss from the
plant reduces plant-water status (but can not recover fully), which hampers plant
growth.
8.5.1.4 Rootstocks and Salinity Tolerance
Most fruit crops are more sensitive to salinity than are field, forage or vegetable
crops. Grapes, citrus, stone fruits, berries and avocados are all relatively sensitive
to salinity. However, certain stone-fruits, citrus and avocado rootstocks differ in
their ability to absorb and transport sodium and chloride ions and have, therefore,
different salt tolerance.
Most fruit crops are also sensitive to other toxic elements, particularly boron.
This ion is present in most irrigation water and in saline soils. It is toxic to many
plants at a concentration only slightly in excess of that required for optimum growth.
Small quantities of boron absorbed by the roots are accumulated by the leaves and
values above 250 ppm result in typical leaf burns.
8.5.1.5 Soil Moisture
As the soil moisture deceases, the concentration of salt, and hence the salinity
increases. The vice versa is true for increasing soil moisture. Thus the soil moisture
affects the plant stand and growth.
8.5.1.6 Soil Type
For a given moisture content, soil-water potential is higher in clay soil than that
of the sandy soil. Thus the plant can easily uptake the moisture from sandy soil
compared to clay soil.
8.5.2 Relative Salt Tolerance of Crops
Some crops are more sensitive to salinity than others. Crops such as pulses, row
crops and special crops are particularly sensitive to salinity. The salt tolerance of
some crops changes with growth stages.
Generally, corn and grain sorghum are intermediate and wheat and alfalfa are
more tolerant. Crested and tall wheatgrass and a few sorghum-sudan hybrids are