Pumpkin is one of the most important medicinal plants. Management practice effects on water and nitrogen use efficiency as well as oil yield have not been well documented for pumpkin. It is thought that reduction of crops production occurs due to shortage of nitrogen and irrigation. Therefore, we applied deficit irrigation to pumpkin with contrasting nitrogen supply. Treatments included three doses of nitrogen supply (120, 180 and 240 kg N ha-1), in combination with three levels of irrigation (300, 600 and 900 mm irrigation water ha-1). Field experiment was conducted at Agricultural Research Station of Bu-Ali Sina University in the growing season of 2012. Water and nitrogen use efficiency; WUE and NUE, and grain and oil yields were measured. The ANOVA revealed that the N and irrigation treatments and their interaction exerted significant effects on WUE and NUE as well as grain and oil yields. With decreasing irrigation water from 900 to 300 mm ha-1 and increasing N rates from 120 to 240 kg ha-1, nitrogen use efficiency decreased significantly. The highest WUE for grain and oil yields were achieved at the pumpkin plants which irrigated by 600 mm water ha-1 and received 180 kg N ha-1. Therefore, it seems that consumption of 600 mm irrigation water ha–1 and application of 180 kg N ha–1 can produce the highest grain and oil yields, while increasing WUE and decreasing N leaching.
