The effect of irrigation and nitrogen top-dressing pattern on yield and growth of sunflower

Abstract

In order to study the effect of irrigation (I0: optimum irrigation, IV and IR: water stress during vegetative and reproductive stages, respectively) and nitrogen (N1: 25% at planting, 50% at eight-leaf stage and 25% at head appearance; N2: 50% at eight leaf stage and 50% at head appearance; N3: 50% planting and 50% head appearance) on yield and growth of sunflower, a split-plot experiment was conducted in 2011 and 2012. Average cross years, IV and IR caused a significant reduction of final dry leaf (20.4 and 34.5%), stem (40.5 and 45.7%) and total weight (25.9 and 28.0%) and also a significant reduction of the grain yield as much as 14.8% and 13.3% in comparison to I0. N1 caused a significant 25 and 14% reduction of the leaf area index in comparison to N3 and N 2; however, the grain yield was not significantly different in N3 and N2 in both years. In I0, N3 caused a significant 34.8% increase of final dry weight of the leaf and an insignificant increase of dry weight of stem and the total weight as much as 30.9% and 16.3%, respectively and also a significant 16.4% reduction of the grain yield in comparison to N2. On the whole, N2 treatment in different irrigation regime caused a higher grain yield in comparison to N1 and N3, but N3 treatment in I0, and N1 in IV and IR reduced the grain yield.