الفهرس 
Effects of nitrogen fertilizationOnly 14 pages are availabe for public view
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Abstract
Two experiments were conducted at a private farm near Nubaria Agricultural Research Station during 1995 and 1996 summer seasons. The experimental design was split plot with four replications. In the first experiment, the cultivars Mayak, Hysun, GlOl and Pioneer were arranged in the main plots, and 45, 60 and 75 kg Nlfed were laid out in the subplots. In the second experiment, three super phosphate levels (zero, 15 and 30 kg Plfed.) were in the main plots and six spray treatments of microelements (Zn, S04, FeS04, MnS04, mixture, greenzit 5 144 and water) were in subplots. The main findings were as follows : Mayak cultivar surpassed the other cultivars in plant height, stem diameter, 100 seed weight and seed yield (kglfed) in the two seasons, head diameter in the first season and crop growth rate (CGR) and relative growth rate (RGR) in the second period of 1995 and at the two periods in 1996. Cultivar Gl 0 1 had the highest values of RGR at the second period in 1996 season, number of seedshead, seed yield kdfed, seed husk %, and cultivar Pioneer exceeded the others in CGR and RGR at first in 1995 season and seed oil content %. Adding 45 kg Nl fed increased significantly stem dry weight % at 75 DAS in 1995 season and at age of 45 days in 1996 season, RGR at (45-60 DAS) in 1996 and seed oil % in the two seasons. Adding 60 kg Nlfed increased significantly specific leaf weight at 60 days in 1995 season. Adding 75 kg Nlfed increased significantly the plant height, dry matter weight, LA and LAI, CGR in both seasons and stem dry weight % at 75 DAS in 1996, leaves dry weight % at 45 DAS in 1996 and head dry weight % in 1995 and all the characters of the yield and its components and oil yield (kglfed). The highest value for seed yield and oil yield were obtained by growing cultivar G 10 1 with 75 kg Nlfed. Adding phosphorus fertilization at the rate of 15 kg plfed with foliar spray of zinc gave the highest seed oil % and seed oil yield in the second experiment.