Splitting of nitrogen application through growth stages in various sunflower cultivars to improve their vegetative growth and seed yield

A field experiment was carriedout in spring seasons of 2012 and 2013 to increase the efficiency of nitrogen application in spite of that no splitting nitrogen has practiced for the studied cultivars. Five splittingtreatments (T1, T2, T3, T4, andT5) of nitrogen application were studied in three sunflower cultivars (Shumos, Akmar, andZehratAl-Iraq). The results showed that Shumoscultivar, T4 treatment of nitrogen application and their interaction gave the highest seedyield (6.3 and 6.43), (5.78 and 6) and (6.62 and 6.9 ton ha-1), respectively, on both seasons. The highest significant correlation value belonged to the correlation between seedyield and leaf area (0.85 and 0.87) for both seasons. It can be concluded that splitting of nitrogen fertilizer during growth stages is effective to increase the efficiencyof nitrogen application and lead to increase seedyield. Also, leaf area could be a selection criterion to improve seedyield.