Influence of foliar zinc application on yield and physiological traits of soybean under different irrigation regimes

In order to study the effect of irrigation regimes and zinc foliar application on some physiological traits and yield of soybean, an experiment conducted in 2009 at Faculty of Agriculture of Tarbiat Modares University as randomized complete block design arrangement in split factorial with three replications. Main factor was irrigation regimes containing three levels (non stress, water deficit stress in vegetative growth stage and water deficit stress from flowering stage to 10 percent pod set) and subordinate factor was a factorial combination of foliar zinc application containing three levels (non foliar application, water foliar application and zinc sulfate (5000 ppm)) foliar application and cultivars containing two levels (L17 and Clarck 63). Water deficit stress significantly decreased the grain yield. Water deficit stress decreased further Fv/Fm, chlorophyll and soluble protein content in leaves of cultivars, but increased soluble carbohydrates, proline content and antioxidant enzymes activity. Zinc sulfate foliar application increased Fv/Fm, chlorophyll content, soluble protein content in leaves and superoxide dismutase activity in both cultivars, but decreased soluble carbohydrates, proline content, catalase and peroxidase activities. In general, foliar application of zinc decreased harmful effects of oxidative stress due to water deficit stress and improved growth conditions for soybean plants.