Effect of irrigation stop at different growth stages on some agronomic traits of sunflower (Helianthus annus) under three plant densities in Takestan Region, Iran

An experiment was conducted in experimental field of Department of Agriculture, Islamic Azad University, Takestan branch, Iran in 2009 to study the effect of irrigation stop at different growth stages on some agronomical traits of sunflower under three plant densities. It was a split plot experiment based on a Randomized Complete Block Design with three replications. The treatments of irrigation stop included irrigation stop at 6-8-leaf stage, at budding stage and at flowering stage as well as control (normal irrigation). The irrigation treatments were regarded as the main plot, and plant density with three levels of 66000, 83000 and 110000 plants/ha as the sub-plot. The studied traits included head diameter, unfilled grain percentage, biological yield, grain number/head, 1000-grain weight, oil content and grain and oil yield. The results showed that different irrigation levels had significant effect on plant height, head diameter, grain number/head, 1000-grain weight and oil content. The lowest amount of all traits was obtained at the treatment of irrigation stop at 6-8-leaf stage. In addition, different plant densities had significant effect on plant height, stem diameter, head diameter, 1000-grain weight and oil content. The interaction between irrigation stop and plant density significantly affected such traits as unfilled grain percentage, biological yield and grain and oil yield. The treatment of normal irrigation at the density of 110000 plants/ha produced the highest grain yield (5033.7 kg/ha) and the treatment of irrigation stop at 6-8-leaf stage at the density of 66000 plants/ha produced the lowest one (528.2 kg/ha). Considering the dependence of oil yield to grain yield, the same treatments produced the highest and lowest oil yield, respectively, too.