Two field Experiments were conducted during 2005/2006 and 2006/2007 seasons at the Experimental Farm of the Faculty of Agriculture, Zagazig University, Zagazig, Sharkia Governorate, Egypt. The study aimed to investigate the response of some wheat cultivars namely Giza 168, Gemmiza 7,Gemmiza 9 and Sakha 93 to three seeding rates which were 300, 400 and 500 grains / m2 under three nitrogen sources included ammonium sulphate, ammonium nitrate and urea in both growing seasons. The most important results could be summarized as follows:
Wheat cultivars differed significantly regarding their plant height and number of spikes / m2, as well as, grain and straw yields and most of their attributes where Gemmiza 9 followed by Gemmiza 7 recorded higher grain, straw and total yields than Giza 168 and Sakha 93, however, the four wheat cultivars showed closer spike length and harvest index.
Increasing planting density from 300 to 400 and 500 grain / m2 significantly increased plant height, number of spikes / m2, grain, straw and total yields / fad but, significantly decreased spike length, number of spikelet / spike, number of grains / spike, thousand grain weight and grain weight / spike. Harvest index was not affected significantly due to raising number of grains / m2.
Addition of nitrogen in the form of ammonium sulphate (AS) was superior to all N forms applied where the highest averages were recorded by ammonium sulphate followed by ammonium nitrate (AN) however the lowest averages were recorded by urea (U) in most characters of yield and yield attributes, but thousand grain weight and harvest index were not affected by varying N sources.
The significant interaction effects between the studied factors indicated that best yield and yield attributes could be obtained by Gemmiza 9 cultivar when dense planting of 400 or 500 grain / m2 and ammonium sulphate were applied.
Grain yield was positively and significantly correlated with plant height, number of spikes / m2, number of spikelets / spike, number of grains / spike, thousand grain weight, grain weight / spike and grain and straw as well as total yields / fad.
Results cleared that the highest yield could be obtained from sowing Gemmiza 9 wheat cultivar when planting with 400 or 500 grain / m2 and ammonium sulphate were applied.