In order to investigate the effect of water stress and different levels of nitrogen fertilizer during different growth stages on grain yield and yield components of maize hybrid SC 704, a field study was conducted. The factorial design of the study comprised of randomized complete block with four replications. Four levels of nitrogen fertilizer (0,200,400 and 600 kg urea h&’) along with four levels of irrigation (water stress imposed at complete appearance of tenth leaf, at 50% tasselling, at post anthesis and an optimum irrigation treatment) were used as treatments. Results showed that water stress significantly decreased grain yield and certain yield components. Water stress also decreased dry weight of ear, ear cob and kernel number per ear row. Maximum corn seed yield resulted when optimum irrigation water was applied. When water stress was imposed at complete appearance of tenth leaf, at 50% tasselling, and at post anthesis, it decreased grain yield by 27, 21, and 11%, respectively. Regarding water use efficiency during water stress, maximum efficiency was observed at complete appearance of tenth leaf but as the plant progressed through tasselling and post- anthesis, water use efficiency decreased. Nitrogen fertilizer significantly affected grain yield and certain yield components. Maximum seed yield was produced with 400 kg urea ha but yield differences among 200, 400, and 600 kg urea h&’ were not significantly different.
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