Two field experiments were carried out at western desert of Sohag Governorate, Egypt (latitude of 26˚ 61' N, longitude of 31º 52' E and altitude of 72 m) in 2015/2016 and 2016/2017 seasons to find out the optimal plant age at harvest (180, 195 and 210 days from sowing) of the three multi-germ sugar beet varieties namely Hosam, Sahar and Kawemiraunder condition of a new reclaimed soil in Sohag. A Randomized complete blocks design using a split-plot arrangement with four replications was used in both seasons, where the main plots were devoted for sugar beet varieties, while plant ages of harvesting were randomly distributed in the sub plots.
The results showed that sugar beet varieties differed significantly in all studied traits. Hosam variety was superior in root length, root yield/fed and root fresh weight/plant in both seasons. However Kawemira variety had the thickest root diameter and heaviest top fresh weight/fed in both seasons, as well as TSS% in the1st one. Sahar variety attained the highest values of sucrose and sugar yield/fed in both seasons, in addition to TSS% and purity%in the 2nd one.
delaying harvesting from 180 up to 210 days from sowing increased significantly root length, diameter and root fresh weight/plant, root and sugar yield/fed as well as TSS and sucrose % in both seasons and purity % in the 1st one. Beets harvested at age of 180 days attained the highest value of top fresh weight/fed in both seasons.
Interactions between sugar beet varieties and ages of harvesting were significant except purity%, in the1st season. In the 2nd one, TSS, sucrose %, root and sugar yield/fed were significantly affected by the interaction between the two factors.
Under the conditions of this work, harvest sugar beet Hosam and Sahar varieties after 210 days after sowing can be recommended to obtain the highest root and sugar yields/fed in the new reclaimed soil in Sohag Governorate.