SALINITY TOLERANCE IN TOMATO - IMPLICATIONS OF POTASSIUM, CALCIUM, AND PHOSPHORUS

The effect of salinity on the growth and yield of tomato plants and mi neral composition of tomato leaves was studied. Five tomato (Lycopersi con esculentum Mill) cultivars, Pearson, Strain B, Montecario, Tropic, and Marikit, were grown in sand nutrient culture. The nutrient soluti ons applied consisted of a modified half-strength Hoagland solution wi th 50 mM sodium chloride (NaCl), 3 mM potassium sulphate (K2SO4), 1.5 mM orthophosphoric acid (H3PO4), and 10 mM calcium sulphate (CaSO4). S tem height and number of leaves of tomato plants were not found to be significantly different but leaf and stem dry weight were reduced sign ificantly in plants irrigated with saline nutrient solution in contras t with control plants. The total yield was reduced in plants that rece ived saline treatments, but there was no significant difference in fru it number and fruit set percentage. The fruit electrical conductivity and total soluble solids were increased in plants irrigated with salin e nutrient solution. Fruit pH was not found to be significantly differ ent among salinity treatments. Mineral composition of tomato leaves we re increased by addition of potassium (K), phosphorus (P), and calcium (Ca) to the saline nutrient solution. The addition of K to the soluti on resulted in an increase in sodium (Na) leaf content. The amounts of K and magnesium (Mg) were not significantly different among salinity treatments. Calcium content was increased when CaSO4 was added. Applic ation of H3PO4 resulted in the highest amount of P in tomato leaves un der saline conditions. The present study revealed that application of K, P, and Ca under saline conditions improved fruit electrical conduct ivity and total soluble solids. Sufficiency levels of the mineral nutr ients K and P were obtained in tomato leaves when the appropriate nutr ient was used in the saline solution.