Comparison of conventional sowing date with late sowing dates on yield and yield components of sunflower cultivars (Helianthus annus L.) in Hamedan climate

To study the effect of sowing dates on yield and yield components of sunflower cultivars as a second crop, an experiment was conducted in Research Field of Education Center of Jihade-Agriculture of Hamedan. The experiment was carried out in factorial based on randomized complete block design with three replications. The first factor was sowing date including 20th May, 25th June and 10th July and the second factor was sunflower cultivar vic. Sirna, Euroflor and Armaviruski. Acoording to the results, there were significant differences in seed and biological yield, head diameter, thousand seed weight in P <0.01 level. Also, there were significant differences in harvest index, number of seeds in head, plant height in P <0.05 lrvel. Conventional sowing date (20th May) had the highest seed yield (495.45 g m-2) and both 25th June and 10th July had the minimum values. Conventional sowing date and 25th June were placed in similar groups based on harvest index, biological yield, number of seed per head and thousand seeds weight traits, but were more than 10th July. About plant height, the highest value related to 25th June. There were significant differences among cultivars about head diameter, 1000-seeds weight (P <0.05) and plant height (P <0.01). The highest head diameter and plant height related to Euroflor and Armaviruski cultivars, respectively. Armaviruski cultivar had the highest plant height in compared with the others. Delay sowing date of 25th June is suggested in this climate of region and it is possible to cultivate all three cultivars in this region after cereal harvesting (especially Barley).