Effect of zinc sulfate application method on maximum leaf area index, yield and yield components of sunflower (Helianthus annuus L.) under water stress conditions

To study the effect of water stress and zinc sulfate application method on maximum leaf area index, yield and yield components of sunflower, an experiment was conducted in 2014 at research station of Bu Ali Sina University as a randomized complete block design with split plot arrangement in three replications. Water stress in four levels (irrigation after 60, 90, 120 and 150 mm evaporation from A pan) was placed in main plots and zinc sulfate application methods (no application, foliar feeding, broadcasting and placement application) were placed as subplots. The results showed that the maximums of leaf area index, head weight, number of seeds per head and grain yield were achieved in low intensity of water stress levels (irrigation after 60 and 90 mm evaporation) plus foliar feeding of zinc sulfate. Nevertheless, at severe water stress conditions, there was not difference between application methods of zinc sulfate fertilizer on measured traits. However, the head diameter and biological yield in severe water stress level (irrigation after 150 mm evaporation) were higher in foliar zinc sulfate application versus other application forms. In this study, seed weight was only affected by water stress treatments and harvest index reduced by reduction in water availability. In this study zinc sulfate especially in foliar application and under water stress improved the most of measured traits and decreased water stress severity on them.