الفهرس 
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Abstract
Two field experiments were carried out at Shandaweell Agricultural Research Station, Sohag Governorate (ARC) in the two successive seasons of 2005/2006 and 2006/2007 to study the effect of nitrogen (210, 240 and 270 kg N/fed.) and magnesium (0.0, 1.0 and 2.0 g Mg/l water) on yield and quality of three sugar cane varieties (the commercial variety G.T.54-9 known as C9, G.95-21 and Ph.8013).
A split-split plots design with four replications was used in both seasons. Sugarcane varieties were allocated in the main plots. Nitrogen levels were randomly distributed in the sub plots, while magnesium fertilizer levels were distributed in the sub-sub plots.
The obtained results can be summarized as follows:
I- Periodical studies:
1- Number of plants/m2 The evaluated sugarcane varieties differed significantly in number of plants/m2 in both seasons. Sugarcane G.95-21 variety surpassed the other two varieties in this trait. Increasing N fertilization level to 270 kg N/fed. increased the number of plants/m2 significantly at age of 150 and 180 days in both seasons except at 150 days from planting in the 2nd season. Number of plants/m2 was significantly influenced by the applied Mg levels at age of 150 days from planting in both seasons and at age 180 days in the 2nd season. Number of plants/m2 was insignificantly affected by the interaction between sugarcane varieties and N fertilization levels in the 1st season and by the 2nd order interactions among the three studied factors at ages of 150 and 180 days in both seasons. However, it was significantly affected by the same interaction at age of 180 days in the 2nd season and the interaction between sugarcane varieties and Mg levels at age of 150 and 180 days, in both seasons.
2- Stalk height (cm) of sugarcane varieties differed significantly. The commercial sugarcane variety G.T.54-9 surpassed the other two varieties and gave the tallest stalks, while G.95-21 variety had the shortest ones.
The sugarcane differed significantly in cane stalk height due to N fertilization levels at all sampling dates in both growing seasons, except at 270 days from planting in the 1st season. Also, a significant increase in stalk height due to the used Mg levels was detected at the four sampling ages in the 1st and 2nd seasons. The interaction between sugarcane varieties and N fertilization levels affected stalk height at age of 210 and 240 days only, in the 1st season. In the 2nd one. This trait was significantly affected by varieties x N levels interaction at 210, 270 and 300 days.
The interaction between varieties and Mg levels had a significant effect on stalk height at the four sampling ages in the 1st season. Stalk height was significantly affected by the interaction between N and Mg levels at age of 270 and 300 days, in the 2nd season only and the interaction among the three studied factors at ages of 270 and 300 days in both seasons.
3- Stalk diameter (cm) of sugarcane varieties varied significantly. The promising sugarcane variety Ph.8013 showed the superiority over the other two varieties and recorded the highest value of stalk thickness, followed by G.T.54-9, while G.95-21 variety had the lowest value of this trait. Stalk diameter increased significantly as affected by increasing the N at all sampling dates in both seasons.
The interaction between varieties and nitrogen levels had a significant effect on stalk diameter at age of 210 days, in the 1st season and at 270 and 300 days in the 2nd one. The interaction between varieties and Mg levels affected this trait significantly at all sampling dates, in the 1st season and at 270 days in the 2nd one. Stalk diameter was significantly affected by the 2nd order interactions among the three studied factors at ages of 210 and 240 days in the 1st season and at 270 and 300 days in the 2nd one..
4- Total soluble solids percentage (TSS%): Sugarcane varieties differed significantly in TSS% at all sampling dates in both seasons. With increasing N and Mg fertilization levels, significant increases were detected in TSS% at all sampling dates in both seasons.
Total soluble solids % was significantly affected by the interaction of varieties x N; varieties x Mg and between the three studied factors at 210 days in both seasons.
5- Leaf area: The tested sugarcane varieties varied significantly in leaf area in both seasons. Sugarcane Ph.8013 variety showed the superiority over the other two varieties in this character. Leaf area increased significantly by increasing the applied N and Mg levels at the three sampling dates in the 1st and 2nd seasons. except at age of 300 days in the 2nd season for Mg treatments.
Leaf area was significant affected by the interaction between sugarcane varieties and N fertilization levels and the interaction between sugarcane varieties and Mg levels, at the three sampling dates in both seasons except at 300 days from planting for sugarcane varieties x N levels in the 2nd season. This trait was significantly affected by the interaction between N and Mg levels at ages of 180, 240 and 300 days in the 1st season only. Leaf area was significantly affected by the 2nd order interactions among the three studied factors at ages of 180 and 240 days, in the 2nd season and at 300 days in the 1st one.
6- Chlorophyll content: The examined sugarcane varieties differed significantly in chlorophyll content in both seasons. Leaves of sugarcane Ph.8013 variety contained the highest values of chlorophyll A+B followed by the commercial G.T.54-9 variety and G.95-21 variety which recorded the lowest values of this trait at ages of 180, 240 and 300 days, in the 1st season. Increasing N and Mg levels increased chlorophyll content significantly in the 1st and 2nd seasons.
Chlorophyll content was significantly affected by the interaction between sugarcane varieties and N fertilization levels in the 2nd season only at ages of 240 and 300 days, and the interaction between sugarcane varieties and Mg levels at the three sampling dates in the 2nd season only as well as the interaction between N and Mg levels at the three sampling dates in both seasons, except at age of 180 days in the 2nd season. This trait was significantly affected by the 2nd order interactions among the three studied factors at age of 240 days, in the 2nd season, and at ages of 300 days in both seasons.