The effect of growth period and stage on quantity and quality of autumn sugar beet (Beta vulgaris L.) in Fasa

For determination of the best growth period and stage of two sugar beet (Beta vulgaris L.) cultivars in order to develop the planting area of this plant in the autumn and investigating the effects of different sowing and harvesting dates on their root and sugar yield and a field experiment was conducted in Fasa regions. The experiment was carried out with the RCBD as the base design at split-split plots consisting of 18 treatments in four replications for three years (2005-2008). Main plots were three sowing dates (September 27th, October 17th and Novamber 6th), sub-plots were two commercial sugar beet cultivars and sub-sub-plots were three harvesting dates (April 30th, May 26th and June 20th). In each plot, the cultivars were planted in four rows with eight meters length and 50cm interval. During the growing period, parameters such as number of plants, lost plants, growth rate and bolting percentage were determined. The root yield was measured by harvesting the roots from the middle of plots (from two rows, each eight meters long). Characteristics such as root yield, sugar content, impurities (K, Na and damaging N in pulp), white sugar percentage, purity of raw extract, alkali index, and molasses were measured. Results showed that bolting percentage of plants in different sowing dates were significantly different (at 1% level of probability). The highest bolting percentage (18.409%) was obtained from September 27th plot. Sowing dates (September 27th and Novamber 6th) had the lowest bolting percentage (5.420% and 2.870%, respectively). The bolting percentage, root yield, sugar content, impurities, purity of raw extract, alkali index, and molasses and white sugar yield of two tested cultivars namely Rasoul and BR1 were not significant. The maximum bolting percentage obtained from the harvesting date (June 20th) was 9.964%. Maximum root yield and white sugar yield was obtained from sowing date (27th of September) and harvesting date (20th of June) which were 58.486 and 5.360 T.ha-1, respectively.