THE EFFECT OF SOWING DATE AND NITROGEN FERTILIZER FORM ON GROWTH, YIELD AND YIELD COMPONENTS IN SUNFLOWER

The purpose of this study was to investigate the effects of sowing date and nitrogen fertilizer forms on the yield and agronomic characteristics of two cultivars of oil sunflower (early, Sirena and late, Teknosol) in Erzurum, Eastern Anatolia of Turkey, in 2013 and 2015. Three sowing dates were established at about 10-day intervals from late-April to early and mid-May (22 April, 2 May and 12 May 2013; and 28 April, 8 May and 18 May 2015). Three nitrogen fertilizer forms ammonium sulfate, ammonium nitrate, and urea were used. The results of this study showed that sunflower seeding from 28 April to 8 May gives more assurance for higher yields. The present results highlighted the practical importance of fertilization with appropriate nitrogen fertilizer forms in seed and oil yield formation in sunflower, and the urea form can be suggested to meet its N requirements. The yield differences measured for three sowing dates and nitrogen fertilizer forms were primarily related to the changes in head diameter and 1000 seed weights. According to the results of this study, early sunflower cultivars, having the highest yield and agronomic characteristics can be recommended for the similar ecological condition of our study region a short growing season and high altitude.