effect of planting date on phenology, grain yield and its components of two sunflower cultivars

effects of different planting on phenology, grain yield and its components of two sunflower culitvars were investigated. in 1996, an experiment was conducted in the experimental field of azad islamic university of khorasgan, located in khatonabad village, isfahan. the experiment was arranged in a randomized complete block design with a split plot layaout and four replications. the main plots consist of four planting date (april 24th, may 9th, may 24th and june 8th) and subplots were arranged for two sunflower cultivars (record and zaria). the results of this experiment showed that there were developmental stages with delay in planting. the record and zaria required 1755 and 1653 growing degree days (gdd) for their physiological maturity respectively. effect of planting date on biological yield and number of seeds per bead were significant and delay in planting reduced them. however seed weight was affected by planting date and increased as planting delayed. the maximum biological yield and seed weight were obtained for record and zaria. the maximum grain yield was obtained in april 24th for record and the minimum grain yield was obtained in june 8th for zaria. on the average, record and zaria yielded 4773 and 4520 kg/ha, respectively. with the respect to the under conditions, planting of record cultivar in april 2lth-27th, is recommended