Two field experiments of sugar beet were carried out at Salcha Agricultural Research Station (Kafr El-Sheikh Governorate) in the two growing seasons of 1997/1998 and 1998/1999, to investigate the effect of Yeast extract preparation, the growth retartends padobutrazol and the two nutrient elements K and Mg, applied at different stages of growth on top, root, sugar yields and juice quality of sugar beet plants. The experiments were laid out in split plot design with three replications. Application dates were allocated in the main plots and foliar application of treatments were distributed randomely in the sub plots. Delaying the foliar application from 45 to 75 and 105 days from planting with studied treatments caused significant increses in top, root, biological and sugar yields of sugar beet. The higher concentration of nutrients and biological activators produced the highest values of yield compared with the lower levels. There was a significant interaction between time of foliar applications and the foliar nutrients treatments. Delaying foliar appliation to 105 days from sowing significantly increased juice quality and produced the highest values of TSS% (25.64), sucrose (17.09) and purity (66.59) and the lowest values were 25.32, 16.79 and 66.23 % for the same juice quality traits, respectively, when foliar spray was carried out after 45 days from sowing. The higher levels of YE, PP333, K and Mg gave the highest values of TSS % 27.16, sucrose 18.81 % and purity 69.29%.