Two field trials were conducted at Tamiea Agric. Res. Station, Fayoum Governorate, Egypt during 2012 and 2013 summer seasons to investigate the effect of three N  fertilization rates, i.e. N₁ : 40, N₂: 50, and N₃: 60 kg/fed as liquid ammonia (one kg of liquid ammonia contains 82.5% N) combined with three levels of irrigation water quantities e.g. 2200, 2500 and 2800 m³/fed distributed during the growing season onto six irrigation events. The adopted treatments were assessed  in a strip- plot design with four replications on yield components, yield and some crop water relations. The main results obtained were as follows: Seed yield and yield components were significantly affected due to N fertilization levels and applied irrigation water quantities in 1^st and 2nd seasons. The highest averages of plant height, head diameter and weight, seed weight/head, 100-seed weight and seed yields (792.15 and 816.49N kg/fed in 2012 and 2013 seasons, respectively), were detected from injecting the soil with liquid ammonia as 60 kgNfed^-1 level and irrigating with 2800 m³ water/fed whereas the lowest yield components, and seed yield (565.61 and 580.52 kg/fed) were obtained with 40 kgNfed^-1 level and applying 2200 m³ water/fed. The highest seed oil content i.e. 42.23 and 42.31 % in 2012 and 2013 seasons, respectively. were obtained due to 40 kgNfed^-1 level.and 2800 m³ water /fed rate interaction. Seasonal evapotranspiration (ET_C) was maximum (50.76 and 51.77 cm in 2012 and 2013) with applying 60 kgNfed^-1 level and irrigating at 2800 m³/fed water interaction. The monthly crop coefficients (K_C) under the highest yielding interaction were 0.57, 0.76, 0.95 and 0.62 for July, August, September and October, respectively, (means of the two seasons). Applying 50 kgN fed^-1 level and irrigating with 2200 m³/ fed rate is the most efficient interaction for water use with values comprised 0.374 and 0.382 kg seeds/ water consumed in 2012 and 2013 seasons, respectively. Moreover, the highest water productivity (WP) values i.e. 0.321 kg seeds/m³ water applied, respectively, in 2012 and 2013 seasons were recorded due to  60 Nkg fed^-1 level and 2200 m³/fed water interaction.