EFFECTS OF PLANTING DATES AND ROW DISTANCE ON SUGAR CONTENT, ROOT YIELD AND SOLAR RADIATION ABSORPTION IN SUGAR BEET AT DIFFERENT PLANT DENSITIES

Two experiments were conducted in 2008 and 2009 in Mashhad, Agricultural Research Station (59 degrees 20' E and 36 degrees 13' N), Esfahan (Khorasan) province, Iran, in order to evaluate the effects of planting dates, row distance and plant densities on yield and yield components of sugar beet. A Split-split plot layout within a randomized complete block design with four replications was used in each year. Main plots were planting dates (May 5th, June 10th), subplots were row distances (50 and 60 cm) and Split-subplots were plant densities (8, 10 and 12 plants per m(2)). In both 2008 and 2009, the highest values of root yield were related to plantation on 5th May. There were not significant differences in sugar content between the two planting dates in 2008 and 2009. However, the value of potassium, sodium and amino-N content of root were lower on 5th May than those of 10th June, in 2008 and 2009. The maximum root yield and sugar content were obtained for 50 cm distance between rows. The highest sugar content and appropriate root yield were achieved in 10 plants per m(2) in both 2008 and 2009. Planting date on 5th May and 50 cm distance between rows obtained higher value for time of maximum light interception and time of final harvesting in both 2008 and 2009. Although, 12 plants per m(2) produced the highest maximum solar radiation absorption in time of maximum light interception and the highest solar radiation absorption in time of final harvesting in both 2008 and 2009, the differences as compared with 10 plants per m(2) were not significant. Plantation on 5th May and 50 cm distance between rows resulted in the highest value for maximum LAI and total dry matter not only in 2008, but also in 2009. Appropriate LAI and total dry matter in these two years were also obtained with 10 plants per m(2). Planting at 50 cm distance between rows and 10 plants per m(2) gave the best yield and yield components. This planting procedure is suggested for fields under the condition similar to the present study.