EFFECT OF NITROGEN FERTILIZATION AND LAST IRRIGATION ON YIELD AND QUALITY OF SUGAR BEET (Beta vulgaris L.) IN NORTHERN DELTA

Two field experiments were carried out  at the Experimental Farm of  EL-Serw Agricultural  Station, Dommiata Governorate ,Agricultural Research Center ,Egypt during the two successive seasons of 2006/07 and 2007/08.The aim of this investigation to study the effect of nitrogen levels at rates of (80,100 and 120 kg N/fed) and three withholding irrigation dates of the last irrigation (3,4  and 5 weeks before harvest) on yield and quality of sugar beet .
The results showed that:
1- There is significant effect of nitrogen fertilizer levels on root diameter, root fresh weight , purity %, root and sugar yields (t/fed)  in both seasons and significant for sucrose percentage in  the second season, TSS% in  the first season while it is insignificant effect  for root length in both seasons. The treatment of 120kgN/fed increased root yield by 64.157 %  and 25.78% and  sugar yield  by 53.23% 21.25% compared by addition 80 kg N/fed in both seasons. 
2- Effect of withholding last irrigation was significant for root length ,sucrose percentage  ,sugar yields in both seasons and significant effect on root fresh weight in the second season and root yield in the  first season and insignificant effect  on purity percentage in both seasons. Applying the irrigation 5 weeks before harvest gave the lowest root length ,root fresh weight and the lowest root and sugar yields while gave the highest sucrose and purity percentages in both seasons.
3- The interaction between  nitrogen fertilizer levels and withholding of last irrigation was significant effect on root length and root fresh weight in the second season ,TSS% in the first season and sucrose percentage in both seasons  ,but it was insignificant effect  on  root diameter, root and sugar yields in both seasons.
4- From this study we can advise to use nitrogen fertilization at rate of 120 kg/fed and date of  last irrigation 4 weeks  before harvest to obtain the maximum yield and quality of sugar beet in East Northern Delta.