Effect of foliar application of zinc sulfate on minerals contenet, seed and oil yields of two safflower cultivars (Carthamus tinctorius L.)

To investigate the effect of zinc sulfate spraying on seed and oil yields of two safflower cultivars، a field experiment was conducted in Ramin Agriculture and Natural Resources University of Khouzestan، Ahvaz، Iran، in 2012-2013 growing season، as factorial arrangement in randomized complete blocks design with three replications. Experimental factors consisted of two safflower cultivars; Soffeh and Local Isfahan and zinc sulfate foliar application at differenet growth stages at five levels; control (without spraying)، spraying at early stem elongation، branching، flowering and seed filling. Results showed that zinc sulfate spraying had significant effect on seed Zn and P contents، chlorophyll a، chlorophyll b، chl-a: chl-b ratio، SPAD value، seed and oil yields and yield components. Spraying of zinc sulfate in different growth stages increased Zn content in seed، however، seed P content decreased. The Zn foliar application significantly increased chl-a، chl-b، chl-a: chl-b ratio، SPAD value، seed oil content and yield، however، there was no significant difference between Zn foliar application in different growth stages. Cultivar × Zn spraying interaction effetc was significant on seed oil content and chl-a. Highest seed oil content in cv. Soffeh obtained in Zn spraying in stem elongation satge and in Local Isfahan in flowering and branching stages. Zn spraying increased head number per unit area and thousand seed weight، with no significant effect on grain number per the head. In general، Zn spraying at all growth stages increased the seed yield، but the differences between growth stages were not significant. Oil yield increased in Zn foliar application compared to control، except for application in seed filling stage. Both of safflower cultivars showed similar response to Zn spraying، but the differences were not significant.