Nitrogen Sources and Rates Effect on Yield, Nutritional Status, and Yield Components of Sunflower

Due to the high levels of crude protein in the achene, sunflower (Helianthus annuus L.) is one of the main oilseeds grown worldwide, particularly for the oil and meal production for animal feed. Despite these advantages, there are few studies on nutrient use efficiency under tropical conditions, especially nitrogen (N). The experiment was conducted in greenhouse conditions to evaluate the effects of N sources and rates on sunflower achene yield (AY), yield and physiological components, and nutritional status of sunflower. The five N sources (calcium nitrate (Ca(NO3)(2)), potassium nitrate (KNO3), ammonium nitrate (NO3NH4), ammonium sulfate ((NH4)(2)SO4), and urea (CO(NH2)(2))), and four N rates (0, 50, 100, and 200mg kg(-1)) were studied. AY was reduced with the ammonia sources application from the 100mg N kg(-1). Plant height and capitulum dry weight (CDW), capitulum diameter, shoot dry weight (SDW), and chlorophyll content were significantly related with N sources and rates. Except for potassium (K), the N rates changed the N, P, Ca, Mg, and S concentration in the leaves and N concentration in achene. In the comparison of sources, on the average of N rates, urea application was more effective than the other N fertilizers in the AY.