Two field experiment were carried out during the two successive seasons of 2008 and 2009 in the Agricultural Experiment Station Farm of the Faculty of Agriculture, Assiut University., to study the effect of three irrigation intervals (15, 25 and 35days), three nitrogen fertilizer rates (40, 80,120 kg N/fed.) and two maize hybrids (Single cross Watania 4 and Three way cross 310) and their interaction on yield, yield components and quality of maize (Zea Mays L.).
The obtained results can be summarized as follows:
 1- Water stress by extending irrigation intervals to 35 days caused highly significant reduction in yield and other studied characters, as well as grain protein percentage but increased number of days to 50 % tasseling.
2- Increasing nitrogen application level up to 120 kg N/fed. caused highly significant increase in grain yield and its components, protein percentage in grains and number of days to 50 % tasseling.
3- Single cross Watania 4 significantly surpassed three way
cross 310 in the mean values of
ear length, grains weight/ear, 100-grain weight and grain yield /fed. in the second season only, except number of days to 50 % tasseling and protein percentage  no significant difference in both seasons.
4- The interaction between irrigation intervals every 15 days and nitrogen fertilizer rate 120 kg N/fed. gave the highest grain yield (ardab/fed) by planting single crossWatania 4.