عنوان مقاله [English]
Short growing season in cold regions is an important factor in not achieving a maximum root yield in sugar beet crop. In an investigation on possible ways to limit the effect of short season culture on the crop, six harvest dates and three sugar beet varieties were considered. The experiment was conducted as a factorial with randomized complete block design in three replications, from 1996-1998 at Ekbatan Research station in Hamedan. Planting dates (The beginning of May) and all cultural practices were kept identical for all treatments. Sugar beet harvest was carried out at selected dates, and data were collected for statistical analysis. Results of ANOVA showed that there were significant differences among sugar beet lines, with BR1 showing the highest: root yield, sugar content and white sugar yield as companed to two other lines. Significant differences were observed for root yield, raw sugar yield, white sugar yield, sugar content, the coefficient of extraction and profit gained in different harvest dates. The two dates of Oct. 12 and Nov. 11, were superior to Sept. 23 and Oct. 2 in all parameters. The highest raw sugar and white sugar content were obtained in Nov. 11 harvest date as compared to others. The highest sugar yield and white sugar yield with 10.09 t/ha and 8.7 t/ha respectively belonged to the harvest of No. 11, which excepted for the No. 1, differed significantly with other harvest dates, coefficient of sugar extraction was increased for the late harvest and the three late harvests, were superior to the early ones regarding average profit obtained in three years and that of the year 2000. Harvest dates of Nov. 11, Nov 1, Nov. 21, Oct 12 and Oct. 2 were respectively 46, 39, 33, 26 and 17% higher as compared to profit of the Sept. 23 harvest date.