Studies were carried in the Research Experimentl farm of the Fa­culty of Agriculture Saba Basha, Alexandria University during 1994/95 and 1995/96 seasons to study the effect of potassium (0.0, 24 and 48 K20/fed) fertilizer as well as the foliar (0.5, 1.0 and 1.5% N) and soil ap­plication (0, 30, 60 and 90 Kg N) of Nitrogen fertilizer on sugar beet plant. Results show that increasing the rate of K fertilizer from zero up to 48 kg K20/fed increased significantly root length, root perimeter, root weight, root/hoot ratio, sugar yield per plant, root and sugar yields ton/fed. Meanwhile, total plant weight, sucrose percentage and purity percentage were significantly increased by increasing potassium level up to 24 kg K20 per fed. Further increase in potassium fertilizer up to 48 kg K20 caused a significant decrease in purity percentage as well as in top weight than those under 24 kg K20/fed. Increasing rate of nitrogen to 90 kg N/fed as soil application or to 1.5% N as foliar application caused a significant increase in root le­ngth, root perimeter, root and top weight per plant, total plant weight, sugar yield/plant, root and sugar yields/fed., T.S.S., Sucrose% and purity % while root/shoot ratio was significantly decreased. There was a significant effect on the interaction between K and N on the root and sugar yields of sugar beet, whereas 48 kg of K20 in combination with 1.5% N as foliar application or 90 kg N/fed as soil ap­plication had superior effect on root and sugar yields of sugar beet.