PLANT-RESPONSES TO SULFATE AND CHLORIDE SALINITY - GROWTH AND IONIC RELATIONS

Growing salt-tolerant crops is one of the more cost-effective strategies for coping with soil salinity, which is a significant factor affecting crop production and agricultural sustainability on the Canadian prairies. This study was carried out to determine if salt tolerance data, generated by traditional CI (NaCl/Cacl2) salinization procedures, are appropriate to the prairies, where SO4 salinity predominates. Barley (Hordeum vulgare L., cv. Bonanza) and kochia [Kochia scoparia (L.) Schrad.] seedlings were grown in sand culture and salinized with either Cl or SO4 salts. The latter system was designed to mimic the natural salinity of prairie soils. The results showed that plant responses to salinity depend on the kind of salts (sulfates or chlorides) contributing to salinity as well as on the total electrolyte concentration. Growth was significantly better (by an average of 17%) on the SO4 system. However, barley salinized with SO4 salts developed severe Ca deficiency at high salt concentrations (electrical conductivity [EC] 17.5-27.5 dS m(-1)) because of low solubility of Ca. Kochia, which is more efficient than barley in absorbing Ca, was not limited by Ca. Barley and kochia tended to have higher selectivity for nutrient cations (Ca, Mg, and K) over Na when the plants were grown on the CI salt system. This may be an indication of a beneficial effect of the high Ca supply in the NaCl/CaCl2 salt system on membrane selectivity. Our results show that there are many possible interactions between salt concentration, salt type, and plant nutrition. The significance of these interactions for salt tolerance testing may vary from crop to crop and may depend on factors such as the nutrient concentration in the growing medium. From a practical standpoint, however, response functions generated by NaCl/CaCl2 salinization probably provide an acceptable measure of the tolerance of most crops to SO4 salinity.