The Effect of Hand Weeding Times on the Reduce of Herbicide Application in Sugar beet

The effect of times of weeding on reducing herbicide dose in sugar beet was studied in 2011-2012 in Jovein. The experiment was conducted in split plot based on a randomized complete block design with three replications. The main factor was herbicide doses (0, 25, 50, 75 and 100% of recommended dose (Chloridazon 3.25 kg. a.i. ha-1 soil applied) and sub plot was times of hand weeding (0, one time hand hoeing, tow times hand hoeing, at 30 and 60 days after plant emergence). Traits like root yield and white sugar yields, impure sugar content, alkalinity coefficient, sodium, potassium, α-amino nitrogen and sugar content in molasses were evaluated. The result showed that the increased frequency of weeding reduced weed density, weed dry weight, α-amino nitrogen and percentage of impure and pure sugar contents, root yield and sugar yield. The least weed density and biomass of weeds were observed in recommended dose. Increasing the doses of herbicide increased impure sugar content (14.48%), α-amino nitrogen (57.86%), pure sugar (19.30%), root yield (77.67%) and sugar yield (111.17%) while it decreased potassium (18.77%), sodium (28.84%) contents and alkalinity coefficient (52.76%) as compared with that of control. For most of the traits, there were not statistically significant difference between the recommended dose and 75% of the recommended dose. Increasing the number of hand weedings reduced herbicide dosages. The, results finally showed that 25% dose reduction of herbicide in one time weeding and 50% dose reduction of it in twice weedings might produce desirable economic yield (root yield).