Effect of planting date and seed rate on yield and yield components of spring rapeseed varieties in late plantingý.

In order to investigate effect of winter sowing date and seed rate on yield and yield components of three spring type rapeseed cultivars an split block design experiment carried out with four replication in 1382-83 and 1383-84 at Esfehan, 1382-83 and 1384-85 at Karaj and 1382-83 at Shahrood. Sowing date considered as main factor including: 10th of Bahman, 20th of bahman and 30th of Bahman. In the second year of experiment at Karaj sowing dates were: the third decades of Bahman, the first decades of Esfand and the second decades of Esfand. Combination of seed rates and 3 spring type varieties were considered as sub-factor. Seed rate levels were: 8, 10 and 12 kg/ha and varieties were: Hyola308(hybrid), Hyola401(Hybrid) and RGS003(open pollinated). Plant height, number of branches, number of pods per stem, number of pods per plant, number of seed per pod, seed weight, grain yield andseed oil content were measured traits. Analysis of variance of the first year experiment at karaj station showed sowing date had significantly effect on pod per plant, grain yield and seed oil content. The highest grain yield with 2385 kg/ha was produced in third sowing date. Seed rate factor only caused significant difference on seed per pod and pod per plant. The highest grain yield with 2266 kg/ha was yielded at 10 kg/ha seed rate. Grain yield of varieties had significant difference and RGS003 with 2321 kg/ha had the highest grain yield but placed with Hyola 401 in the same rank. Analysis of variance of the second year experiment at karaj station showed sowing date had not significantly effect on grain yield, but had on seeds per pod, pods per plant, pods per branches, number of branches and harvest index. The highest with 1619 kg/ha obtained in first sowing date Harvest index, seeds per pod, pods per plant and pods per branches also were higher in first sowing date. Seed rate had only significantly effect on seeds per pod. The highest grain yield among seed rate levels obtained from 12 kg/ha with 1651 kg/ha. The most seeds per pod came from 10 kg/ha of seed rate. Varieties had significantly differences in all recorded traits. Hyola308 with 1618 kg/ha had the highest grain yield and Hyola 401 and RGS003 were placed in other rank. Combined analysis of variance of two years experiment at Esfehan station showed that grain yield was significantly affected by sowing date, seed rate and varieties. The second sowing date(20th of Bahman) with 2842.4 kg/ha had the highest grain yield. The seed rate of 12 kg/ha produced 2733.3 kg/ha grain yield which was the highest and RGS003 with mean yield of 2719 kg/ha produced significantly the high grain yield among other varieties. Seed oil content only was affected by sowing date factor and the highest belonged to the last sowing date (30th of Bahman). The results of analyses of variance of the Sahrood experiment showed that the sowing date of 20th of Bahman yielded the highest grain yield(1342 kg/ha) which had significant difference with other sowing dates. Among the varieties, Hyola308 with mean yield of 1148 kg/ha with significant difference had the most grain yield. Grain yield was also significantly affected by seed rate and 10 and 8 kg/ha of seed rate produced 1120 and 1116 kg/ha grain yield respectively. No result collected at Qazvin station due to cold damage.