Two field experiments were conducted at Sakha Agricultural Research Station Farm, Kafr El-Sheikh Governorate, Egypt (31o05' N latitude and 30o56' E longitude) during 2009/2010&2010/2011 winter seasons to investigate the response of some wheat varieties to different N levels. Split plot design with four replicates was applied, the main plots were assigned to four wheat varieties, Gimiza 9, Giza 168, Sakha 61 and Sakha 93. The subplots were assigned to four nitrogen levels of 0, 30, 60 and 90 kg N/fed. (fed. = 0.42 ha.).
The obtained results can be summarized as follows:
1-Wheat varieties significantly differed in grain, straw and biological yields, as well as harvest index, N%, N uptake and protein content in the two seasons.
2-Gimiza 9 variety had the highest mean value of grain, straw and biological yields, and N uptake and protein content of grain and straw.
3-The grain, straw, biological yields, N uptake and protein content were significantly increased by increasing N levels.
4-The interaction between wheat varieties and N levels showed that Gimiza 9 variety had the highest value of grain yield (2822.0 kg/fed) followed by, Giza 168 (2681.0 kg/fed.), Sakha 93 (2552.0 kg/fed.),and Sakha 61 (2475.0 kg/fed.), with N90 level.
5- The highest N uptake and protein content of grain and straw were obtained by Gimiza 9 with N90 level and the lowest value by Sakha 93 under N0 level .
6-Gimiza 9 had the highest net return value of 8663.75 L.E./fed. followed by Giza 168 (7776.55 L.E./fed)., Sakha 93 (7057.05 L.E./fed.) and Sakha 61 (6769.15 L.E./fed.) with N90 level.
7-The values of net return of fertilizer had the following order : Giza 168 > Sakha 93 > Gimiza 9 > Sakha 61