Effect of split application of nitrogen fertilizer and harvest time on theroot yield and quality characteristics of sugar beet

Effect of split application of nitrogen fertilizer and harvest ime on the root yield and quality characteristics of sugar beet cv 7233 was studied under sprinkler irrigation system in Juvein Plain, Sbzavar, Iran. Five levels of split applications of nitrogen (N1: 25% at planting + 75% at thinning time, N2: 50% at planting + 50% at thinning time, N3: 25% at planting + 50% at thinning time + 25% at 20 days after thinning, N4: 100% at thinning time, and N5: 50% at thinning time + 50% at 20 days after thinning) were assigned to the main plots. Four harvest times (from late August to late November with one-month intervals) were randomized in sub plots as split plot arrangement in randomized complete block design with four replications in three years (1998-2000). Combined ANOVA showed that the effect of split application of nitrogen on root yield and quality characteristics of sugar beet was not significant. Harvest time had significant effect on all sugar beet traits, except root impurities. There was no significant effect of split application of nitrogen×harvest time on plant characteristics. Delay in harvest time increased root yield and white sugar yield from 40 and 3.9 t ha-1 in the first harvest (late August) to 68 and 8.27 t ha-1, in last harvest (late November), respectively. Sugar content also increased from 12.8% in the first harvest to 15.2% in last harvest. In conclusion, it may be suggested that sugar beet in the Juvein region is harvested from late October and whole nitrogen fertilizer is applied after sugar beet thinning at 4-6 leaf stage under sprinkler irrigation system.