Influence of Sodium and Potassium Fertilizers on Growth and Nutrient Contents of Tomato Plant in South Western Nigeria .

The influence of sodium (Na) and potassium (K) on growth and nutrient content of tomato was investigated on the field between 2003 and 2004 at the Teaching and Research Farm, Obafemi Awolowo University. The experiment was a 4 x 3 factorial arranged in Randomized Complete Block Design (RCBD) with three replications. The factors and levels were 0, 4, 16 and 32 mg Na kg-1 soil and 0, 64 and 128 mg K kg-1 soil applied as NaCl (analytical grade) and KCl (muriate of potash), respectively. Nitrogen and phosphorus at the rate of 30 kg N ha-1 and 90 kg P2O5 ha-1 as urea and single super phosphate, respectively, were applied as basal treatments at four weeks after transplanting. Soil properties were determined prior to experimentation. The nutrient contents of the shoot and root were also determined. The nutrient deficiency and toxicity symptoms were recorded. The number of leaves, branches and flowers were also recorded. Nitrogen, phosphorus, calcium, magnesium and sodium content of shoot and roots were determined after fresh fruits have been harvested at 5 months after transplanting. The results showed scorching and curling of leaves at 32 mg Na kg-1 soil. Bigger, brightly coloured and firmer fruits were obtained at Na and K combination of 16 mg kg-1 and 64 mg kg-1 soil at ratio of 1:4, which gave shoot content of 2.24, 2.32, 16.84, 9.57, 2.33 and 0.17 mg g-1 dry weight for N, P, K, Ca, Mg and Na, respectively. A significant decrease of N content and increase in Ca content at the application of 16 to 32 mg Na kg-1 and 64 to 128 mg K kg-1 soil resulted in imbalance in nutrient composition and an adverse effect in growth, fruit yields and quality. Tomato plant roots contained higher Na content than the shoot. Fruit yield correlated strongly with number of leaves (r = 0.88***), number of flowers (r = 0.58*) and number of branches (r = 0.55*). Shoot-N (r = 0.62**) and root-P were positively correlated with all growth parameters and fruit yield. It was concluded that application of Na and K at ratio 1:4 promoted balanced nutrient content in the tomato plant, and hence recommended for improved tomato plant growth yield and quality.