Effect of deficit irrigation on some morphological characteristics and biological yield of spring safflower cultivars

In order to evaluate the effect of limited irrigation on some morphological characteristics and biological yield of spring safflower cultivars, an experiment was conducted in a spilt plot arrangement based on randomized complete block design with four replications at Research Farm of Faculty of Agriculture, University of Birjand during 2008. Irrigation levels (whole season irrigation, and irrigation till grain filling, flowering, and heading-bud stages) and cultivars (Mahali Isfahan (a local variety), Isfahan28 and IL111) were arranged as main- and subplots, respectively. Results showed that reduction in plant height, the height of first branch from soil surface, number of nodes in main stem and number of primary and secondary branches were observed only in irrigation until heading-bud treatment, but primary and secondary heads diameter and biological yield decreased in all of the irrigation cessation treatments. Safflower cultivar also significantly influenced these traits. The highest plant height, the height of first branch from soil surface, number of nodes in main stem and number of primary and secondary branches and biological yield were obtained at Mahali Isfahan cultivar, indicating its promising production potential in arid and semi-arid regions. In addition, reduction of morphological characteristics and biological yield in all three cultivars were observed in irrigation until heading-bud treatment. It seems that this growth stage is the most susceptible period to water shortage and irrigating at this stage under such a condition can significantly enhance the biological yield.