Studies On Salt Tolerance Of Some Field Crops, Limits Of Salt Toxicity

Soil salinity is one of the important factors affecting the growth and yield of most field crops. Sesame and kenaf plants, relative to other crops, are considered sensitively and moderately salt tolerant respectively. The presence of salts in the root medium is well known to have adverse effects on plant growth and yield. So salinity effects on growth and yield may be a direct result of increasing soil moisture stress or of disturbance of nutrient balance or of both (Kapp,1947, Hayward &Wadleigh, 1949 and Bakr Ahmed et al., 1971). To account the effects of salinity on plant growth, three theories have been proposed. In the first, soluble salts in soils decrease the free energy of the soil water, thereby decreasing the availability of water to plants, (Bernstein and Hayward 1958). The basis of the osmotic adjustment theory is that growth inhibited by an excess of solutes taken up by plants from saline media The energy spent by plants to maintain turgor pressure pressure is at the expense of growth (Slatyer 1961). Finally, salts may exert determental affects on plant growth through the toxicity of one or more specific ions present in higher relative concentrations (fenn, et al. 1970). Their influence is essentially of a physiological nature. None of these theories completely explain all the mechanisms affecting plant physiology in turn decreasing plant growth and yield Successful agriculture in saline and alkali soils requires the use of crops capable of producing a satisfactory yield under moderate intensities of salt or alkali accumulation . The present investigation has been undertaken to Study salt tolerance of seame and kenaf crops particularly to determine limits of salt toxicity and their effect on the quantitatve changes of some morphelogical and physiogical characteristics of sesame and kenaf plants grown under different levels of soil mosisture at different stages of growth.