Responses of phenological and physiological stages of spring safflower to complementary irrigation
In order to investigate impact of complementary irrigation on phenological stages, chlorophyll content, radiation absorption and extinction coefficient, as well as some aspects concerning the yield of spring safflower, a split-plot experiment based on randomized complete block design with three replication was conducted at the Ardabil Research Center For Agriculture And Natural Resources, Ardabil, Iran in 2009. Experimental treatments included irrigations (non- irrigation, irrigation at the head appearance and irrigation at the flowering stage) and safflower cultivars (Jila, native Isfahan and Pi-537636). Irrigation levels showed significant effects on flowering initiation, flowering period, seed filing period, maturing, number of head, number of seed per head, shoot dry weight, seed yield, extinction coefficient, radiation absorption and chlorophyll content. There were significant differences among cultivars in terms of head appearance, flowering, flowering period, maturing, number of head per plant, number of seed per head, shoot dry weight, seed yield per plant and seed oil content. Also, interactions between irrigation and cultivar were significant for flowering period and seed yield. The highest flowering period was observed by applying irrigation at the head appearance for the native Isfahan cultivar which caused the highest seed yield at the flowering stage. Complementary irrigation increased chlorophyll content and radiation absorption and decreased extinction coefficient at both stages compared to no irrigation.
Key words: Safflower, complementary irrigation, absorption of radiation, extinction coefficient.