EFFECTS OF NITROGEN AND POTASSIUM FERTILIZER RATES ON YIELD, YIELD RELATED TRAITS AND FRUIT QUALITY OF TOMATO (Solanum lycopersicum L.) AT DIRE DAWA, EASTERN ETHIOPIA

Tomato is an important cash crop produced in many parts of Ethiopia. However the national yield is rated as very low as compared to the entire world. Imbalance as well as improper fertilizer application rate and type is among the major factors constraining tomato fruit yield and quality during production. Therefore, a field experiment was conducted in 2017/18 in Dire Dawa, eastern Ethiopia to assess the effect of nitrogen and potassium fertilizer rates on yield and fruit quality of hybrid tomato variety; and to identify economically feasible fertilizer rates for tomato production. Factorial combination of five nitrogen rates (0, 50, 100, 150 and 200 kg Nha-1 ) and three potassium rates (0, 60 and 120 K2O) were laid out in randomized complete block design with three replications. Analysis of the results revealed that all phenological parameters were significantly influenced by the main effect of nitrogen. Nitrogen and potassium interacted significantly to affect plant height. The main effect of nitrogen and potassium significantly affected leaf area index, number of cluster plant- , 1 total, marketable and unmarketable fruit number and weight plant-1 . Nitrogen and potassium interacted significantly to affect total, marketable and unmarketable fruit yield per hectare. Significantly maximum total yield (144t ha-1 ) as well as marketable yield (132.96 t ha-1 ) was obtained from combinations of 200 kgha-1N and 120 kgha-1K2O. Quality parameters; pericarp thickness, total soluble solids, sugar to acid ratio, power of acidity and ascorbic acid were significantly affected by the main effect of the two factors. Titratable acidity significantly affected by the interaction of the two factors. Economically feasible marketable fruit yield (118494 kg ha-1 ) was obtained from combination of 200 kg ha-1 N and 60 kg ha-1 K2O which gave economic benefit of 822818 Birr ha-1with marginal rate of return 21636.8%. From this experiment combination of 200 kg N with 60 kg K2O ha-1 which showed economically feasible and promising results could be recommended for production of tomato at Dire Dawa and similar areas.