Two field experiments were conducted during ،1991 and 1992 seasons.at the Agricultural Research and Experiment Center. Faculty of Agriculture. Moshtohor. Zagazig University to study the effect of nitrogen source and time of
application on growth. yield and yield components of maize. Giza 2 variety. N addition as ammonium nitrate or urea showed a favorable effect in improving growth. yield and yield components of maize as compared with the addition of calcium nitiate. The highest values of maize growth and yield characters were recorded with the addition of ammonium nitrate and the lowest values were associated with calcium nitrate. Split application of N fertilizer as: T,. 1/3 N at planting + 2/3 N before
the ،st irrigation, followed b T4: 2/3 N before the l5j irrigation + ،/3 N before the 2nd. irrigation or T1: 1/3 N at planting ± ،/3 N before the irrigation + 1/3 N before the 2nd irrigation were superior to applying all amount of N before the Eii. irrigation (T3) on the growth. yield and yield components. Interaction effects between N source and time of application on growth. yield and yield components were not significant in the two seasons. except on shelling percentage in the first season. and car diameter in the second one. Under the conditions of the study. it can be concluded that supplying plants with N fertilizer as amnionluni nitrate in split doses. during the first 6 weeks from planting.