WATER STRESS AND K NUTRITION EFFECTS ON GROWTH INDICES AND SEED YIELD OF SUNFLOWER

In order to study the effect of water stress and potassium levels, growth indices and yield of sunflower a split plot experiment based on randomized complete block design(RCBD) was conducted with four replications during 2011 growing season in Bojnourd International Airport’s field. Water stress was applied by irrigation regimes as main factor at three levels, 60, 90, 120 mm evaporation, from Class A evaporation Pan, and four K+ levels (0, 70, 140, 210 kg/ha K+ as potassium sulphate) as sub plots. The important growth indices i.e. Leaf area index (LAI), total dry matter (DM), Crop growth rate (CGR), plus seed yield was determined. The highest seed yield was obtained from the interaction between K210× I60mm about 4.79 t/ha, and the lowest one in K0× I120mm with 1.70 t/ha. The more potassium nutrition, the more compensation of moisture stress adverse effects and reduction of yield loss. There was a positive relationship between growth indices and seed yield, so increasing of K+ nutrition resulted to higher DM, LAI and CGR, then seed yield. The highest quantities for these three indices were 4.5, 800 gr/m2 , and 15.5gr/ m2 .days, respectively.