Effect of nitrogen and sulfur fertilizer application on yield, yield components, and some physiological traits of spring safflower

In order to study the effect of different levels of nitrogen and sulfur fertilizers on yield, yield components, content of some elements, qualitative and quantitative traits of spring safflower (Serin cv.) an experiment was conducted at agriculture and natural resource research station of Ardabil in 2008. This experiment was carried out in factorial experiment in completely randomized block design with three replications. Nitrogen fertilizer levels included 0, 50 and 100 kg ha^-1 and sulfur was 0, 25 and 50 kg ha^-1. Results showed that application of nitrogen and sulfur fertilizers has significant effect on yield, yield components, so that nitrogen fertilizer application caused to increasing the number of lateral branches, number of capsule, 100-seed weight, seed yield, biomass and harvest index. Some of traits had no significantly differences in 25 and 50 kg per hectare sulfur fertilizer. Also, using of sulfur did not affect harvest index, but the plant height and distance of the first branch from the ground level were significantly different by nitrogen and sulfur application so that, the highest plant height was observed in combination of highest amounts both of nitrogen and sulfur fertilizers. The Leaf relative water content increased with increasing nitrogen and sulfur fertilizer. The highest leaf area index obtained with 100 kg N ha^-1, but application of 25 and 50 kg ha^-1 nitrogen had no significantly effect on LAI. Light extinction coefficient was decreased by applying both N and S fertilizers but light use efficiency was increased.