Radiation Use Efficiency of Autumn-Swon Sugar Beet (Beta vulgaris L.) Under Variable Growth Duration

This study was conducted to investigate the light-use efficiency (LUE) of the fall sugar beet under changing conditions during the growth period in 2009-11 cropping seasons at Safiabad agricultural research center of Dezful-Iran. Treatments included three sowing dates: 27th September, 14th October and 31th October in 2 harvest dates: 215 and 235 days after germination (DAG) (six treatments in total) as a split-plot design with four replications. Radiation received, leaf area index (LAI) and total plant dry matter (TDM) were recorded in two weeks intervals during the growth period. Results showed that sowing and harvest dates and their interaction affected the LUE significantly (at P?0.01).The highest LUE (1.35 ?g/J) achieved in 27th September sowing date and harvesting the crop at 215 DAG. Harvesting the crop at 235 DAG reduced the LUE in 27th September & 14th October sowing dates while it increased the LUE in 31th October sowing date. The LUE reached its maximum in 110 DAG for 27th September & 14th October sowing dates, whereas in 155 DAG for 31th October sowing dates.