This study was carried out in 2003 to investigate the effects of different water regimes (40, 60, 80, 100 and 120 percent of water requirement) and different amounts of nitrogen (60, 120 and 180 kg/ha) as well as their interaction on quantity and quality of tomato (variety Early Urbana). The experiment was performed on the research farm of agriculture faculty of Tehran University (semi-arid area) on a clay–loam soil, using a split plot design with three replications (irrigation treatments as main plots and different amounts of nitrogen as subplots). The results obtained from statistical analysis indicated that the different treatments of irrigation and nitrogen as well as their interactions have significant effect on tomato quantity traits including total yield, marketable yield, number of fruit per plant, average fruit weight and Water Use Efficiency (WUE). The maximum marketable yield and WUE were obtained at 100% water requirement, along with 120 kg/ha nitrogen. Also, the different treatments of irrigation and nitrogen as well as their interactions exert significant effects on tomato quality characteristics including early ripening, fruit dry matter, total soluble solids, titrable acidity pH, of fruit, vitamin-C, fruit firmness and fruit N-NO3. Finally, by considering our conditions of the test place and tomato variety, it is recommended to use water requirement of 80%, along with 120kgN/ha for optimization of crop’s quantity and quality characteristics.
)