PLANTING DENSITY AND NITROGEN RATES OPTIMIZATION FOR GROWTH AND YIELD OF SUNFLOWER (HELIANTHUS ANNUUS L.) HYBRIDS

Planting densities and nitrogen application rates are the major production factors contributing to the final yield of crops especially for sunflower being a non branched plant. Experiments were conducted to assess the effects of planting densities & nitrogen rates and their interaction on growth and yield of two sunflower hybrids during spring season, 2010 and 2011. In treatments, there were two hybrids (Hysun-33 and S-278), two planting densities, 8.33 and 5.55 plants m(-2) (20 and 30 cm plant spacing) with three levels of nitrogen (100, 125 and 150 kg N ha(-1)). The Split split plot design was used for layout of trial. The results showed significant difference for both of the hybrids in all the studied parameters except, number of plants m(-2) in both years of experiments. In comparison of hybrids, S-278 was highest for yield and yield components while less in plant height. Averaged overall of both the years of trial, Maximum achene's yield (3.39 t ha(-1), 2.80 t ha(-1)) was recorded for S-278 and Hysun-33 hybrid, respectively. Increasing plant density increased the final achene, s yield whereas, head diameter, 1000-achene's weight and seed yield per plant decreased. The Nitrogen application markedly enhanced growth and yield by affecting plant height, head diameter and thousand achene's weight. The interaction between hybrids x planting densities, and hybrids x nitrogen was significant for plant height, head diameter and achene's yield ha(-1) but non-significant for 1000-achene's weight and plant population m(-2). Among hybrids the overall yield response of S-278 was highest at plant spacing 20 cm (8.33 plants m(-2)), with125 kg ha(-1) nitrogen application levels in both years.