Effect of the Nitrogen Rate and Weed Control Treatments on the Quantitative and Qualitative Yield of Sugar Beet

Abstract

The effect of nitrogen rate and weed control treatments on the quantitative and qualitative yield of Sugar beet was studied at a private farm on the Oran Kohne River near Joghatai, Razavi Khorasn province, Iran in 2015. This experiment was carried out following a split plot design with three replications. Factors were the rate of nitrogen application and the control of weeds. The nitrogen rates were one and two times the recommended dose (200 kg N ha^–1). Weed control treatments consisted of (1) a weedy check, (2) hand-hoeing twice, 3 and 6 weeks after sugar beet emergence (WAE), (3) hand-hoeing three times, at 3, 6 and 9 WAE, (4) post emergence application of the Phenmedipham+Ethofumesate+Desmedipham (Betanal progress OF) at 3 WAE + one hoeing at 6 WAE and (5) one hoeing at 3 WAE + Betanal progress OF application at 6 WAE. The increase in the amount of nitrogen reduced the density of the weeds, the impure sugar content while increasing the yield of the root, the yield of sugar, the content of a-amino and sodium. The dry weight of the weed, the sugar content in the molasses and the potassium content were not affected by the amount of nitrogen. The results showed that weed management treatments had a significant effect on all traits, except for the sodium content. In “weedy” treatment, weed density and weed dry weight were 41% and 60% higher than in the other weed control treatments, respectively. Weed interference decreased root yield (62%), sugar content (31%) and sugar yield (76%). In general, all weed control treatments improved root yield compared to the non-weeded check. However, the highest yields of root and sugar were obtained by hand hoeing three times at 3, 6 and 9 weeks after the emergence of the sugar beet.