EFFECT OF NITROGEN FERTILIZER AND COMPOST RATES ON YIELD AND QUALITY OF SUGAR BEET GROWN IN SANDY SOIL UNDER DRIP IRRIGATION SYSTEM

In order to investigate the effect of four nitrogen fertilizer rates i.e. 35, 70, 105 and 140 kg N/fad., and four compost rates i.e. 0, 2, 4 and 6 t/fad., and their interactions on yield and its attributes as well as quality of sugar beet (Beta valgaris L.) variety Top, grown in sandy soil under drip irrigation system. Two field experiments were conducted at the Agricultaral Researsh Station, Fac. Agric., Zagazig Univ., at El-Khattara Region, Sharkia Governorate, Egypt during the two successive winter seasons of 2011/2012 and 2012/2013. Regarding to the combined analysis of the both seasons, it could be noticed that increasing N fertilizer level from 35 to 140 kg N/fad., significantly increased root diameter, fresh top weight/plant, fresh root weight/plant, Na (%), K (%), alpha amino-N (%), top, root and recoverable sugar yields/fad. Root length and sugar loss in molasses percentage (SLM%) were responded only to 105 kg N/fad. The highest averages of sucrose and extractable sugar percentages were obtained by application of either 35 or 70 kg N/fad. Whereas, purity percentage significantly decreased with each increase in nitrogen fertilizer levels. Results clearly revealed that increasing compost rates up to 4 t/fad., significantly increased root length and diameter, fresh top weight/plant, fresh root weight/plant, Na (%) and SLM (%). The highest top, root and recoverable sugar yields as well as alpha amino-N (%) were achieved by application the highest rate of compost (6 t/fad.). The highest averages of sucrose, purity and extractable sugar percentages were obtained by the control treatment. In addition, the interaction between nitrogen fertilizer and compost rates significantly affected root length and diameter, fresh top weight/plant, fresh root weight/ plant, purity percentage, top, root and recoverable sugar yields/fad. It could be summarized that N-fertilizer level of 105 kg N/fad., with application of compost at 6 t/fad., could be applied for maximizing sugar production and minimizing soil pollution by reducing the application of N- fertilizer.