Physiological Role of Antioxidants in Improving Growth and Productivity of Sunflower under Different Sources of Nitrogen Fertilizers

A TWO FIELD trials were conducted at Sakha Agricultural Research Station 31° 07 N and 30° 57, Kafr El-Sheikh, Egypt to determine the effect of foliar application of some antioxidants and different sources of nitrogen fertilizers on growth, yield and its components of sunflower (Helianthus annuus L.) cultivar Sakha 53 during the two successive summer seasons 2014 and 2015. A split plot design with four replications was used in the present work. The main plots were randomly assigned to three different sources of nitrogen (urea, ammonium nitrate and ammonium sulfate).Sub plots were randomly devoted to antioxidants treatments i.e. spray with water as control , spray with 150 and 300 mg L^-1 of ascorbic acid and spray with 250 and 500 mg L^-1 of citric acid. The results revealed that, different nitrogen sources significantly affected growth, yield, yield components and yield quality of sunflower plants during the two seasons. Remarkable results noticed at nitrogen sources ammonium sulfate followed by ammonium nitrate and urea. Also, applications of the antioxidants (ascorbic acid and citric acid) were very effective in improving growth characters namely plant height, stem diameter, head diameter ,leaf area plant^-1,seed yield kg fad^-1, seed oil %,seed protein % and plant pigments in relative to the control treatment.