Study of effects of planting and harvesting dates on quantity and quality of monogerm sugarbeet seed in Firoozkooh, Iran

An experiment was conducted in research field of Firoozkooh sugarbeet elite seed production station in 2004 to study the effects of different planting and harvesting dates on quantity and quality of sugarbeet monogerm seed. The experiment was a split plot experiment based on a randomized complete block design with four replications. The planting date at three levels (March 18, April 15 and April 29) made the main plot and harvesting date at four levels (harvesting 15, 30, 45 and 60 days after 50% flowering) constituted the sub-plot. After harvesting and threshing, raw seed yield, seed distribution in terms of diameter and thickness and germination percentage were measured. The results showed that the change in planting date significantly affected the occurrence of 50% greening, stem-bearing and flowering in terms of days after planting and intercepted growing degree days (GDD) at 1% probability level, so that the delay in planting date decreased the number of days to 50% greening, stem-bearing and flowering. The main effects of planting and harvesting dates and their interactions had a significant effect on raw seed yield at 1% probability level. The highest sugarbeet raw seed yield (1164 kg/ha) in Firoozkooh was obtained by planting seed-bearing plants in March 18 and harvesting them 45 days after 50% flowering. The delay in planting date significantly decreased the loss caused by seed polishing, while harvesting date significantly af-fected the proportion of undersized seeds so that it decreased as the harvesting date was retarded. The results indicated that the studied factors did not significantly affect the proportion of standard (with diameters of 3.5-4.5 mm) and oversized seeds (with diameter of >4.5 mm). Delayed harvesting date significantly increased seed germination rate while the change in planting date had no effect on this trait.