EFFECT OF INCREASING POTASSIUM LEVELS FOR ALLEVIATING SODIUM-CHLORIDE STRESS ON THE GROWTH AND YIELD OF TOMATO

The efficacy of using various levels of potassium (K) (4, 8, and 16 mM) under saline conditions to alleviate the detrimental effects of salt-stress were studied using five tomato (Lycopersicon esculentum Mill) cultivars, Strain 19', 'Pearson', 'Montecarlo', 'Maruthuam', and 'Pusa Rub'. Results of the study revealed that 50 mM sodium chloride (NaCl) in a Hoagland nutrient solution significantly reduced stem height, fruit weight, and whole plant dry weights, but increased number of fruits/plant and improved fruit quality by increasing total soluble solids. It did not significantly affect leaf count, percent fruit set, or dry weight. The addition of 4, 8 and 16 mM potassium nitrate (KNO3) to the nutrient solution containing 50 mM NaCl resulted in sodium/potassium (Na/K) ratios of 12.5, 6.3, and 3.1, respectively. The Na/K ratios of 12.5 and 6.3 produced significant improvement in stem height, percent fruit set, number of fruits/plant, fruit weight, and whole plant dry weight. The Na/K ratio of 3.1 was found to be detrimental as it resulted in sharp reduction of plant dry weight compared to the control. Percent total soluble solids was not significantly affected by the addition of any level of K to the saline nutrient solution. The performance of the tomato plant grown under saline conditions supplemented with K in the nutrient solution indicated a higher response at the lowest K concentration used in this study.