Tolerance of Plants to Salinity

Soluble salts tend to accumulate in soils in arid regions and are a potential hazard wherever irrigation is practiced. Plant response is primarily determined by the osmotic pressure of the soil solution to which the electrical conductivity of the saturation extract of soils is closely enough related to provide a useful index of salinity. Specific ion effects, involving nutrition or direct toxicity, affect certain crops under some conditions. Climate, irrigation frequency, and other management practices may modify the salt tolerance of plants. Varietal differences in salt tolerances are not usually of practical importance for most crops, but rootstock specificities regulating the accumulation of potentially toxic ions are of major importance for many fruit crops. Because soil management factors profoundly influence the degree of salt accumulation, plant response to a given irrigation water cannot be predicted without taking into account the probable effects of the conditions under which the water will be used on the resultant level of soil salinity. Soil solutions are often five or ten times more concentrated than the applied irrigation water. The use of more saline water requires that larger quantities of water be applied to promote leaching and to minimize the relative degree of salt accumulation in the root zone of the crop.