Abstract :
To determine the effects of different levels of nitrogen and phosphorus fertilizers on the seed yield of new safflower cultivars, a study was carried out at two different dryland research stations in Iran (Maragheh and Sararoud) for two years (2004-2005). The experiment compared four nitrogen fertilizer levels (0, 30, 60 and 90) kg.ha-1 and three phosphorus fertilizer levels (0, 30 and 60) kg.ha-1 in two safflower genotypes (V1, S-36 and V2, 79-299) in Maragheh and two safflower genotypes (V1, PI-37598 and V2, S-541) in Sararoud, in a factorial random complete block design with 3 replications. Nitrogen fertilizer was supplied as urea (45% N) and phosphorus fertilizer as triple super phosphate (46% P2O5). In each year, the crop was harvested after maturity and mean yield was analyzed statistically. In Maragheh, the results indicated that increasing nitrogen fertilizer increased seed and biomass yield whereas phosphorus fertilizer did not affect yield. In the interaction of variety with nitrogen and phosphorus fertilizers, application of 90 kg.ha-1 nitrogen and 60 kg.ha-1 phosphorus in 79-299 led to the highest seed yield (961 kg.ha-1) and treatment with 90 kg.ha-1 nitrogen and no phosphorus led to the highest biomass yield (4173 kg.ha-1). In Sararoud, increasing nitrogen fertilization did not increase seed yield but did increase plant height. In the interaction between nitrogen and phosphorus fertilizers, the use of 60 kg.ha-1 nitrogen and 30 kg.ha-1 phosphorus led to the highest seed yield (1283 kg.ha-1). Based on the amount of precipitation and yield in different years, we recommend the application of 90 kg.ha-1 nitrogen fertilizer together with 30 kg.ha-1 phosphorus in Maragheh regions, and 60 kg.ha-1 nitrogen fertilizer together with 30 kg.ha-1 phosphorus in Sararoud drylands for safflower production. We conclude that safflower seed yield differed depending on nitrogen fertilization in Maragheh. However, phosphorus fertilization did not increase safflower seed yield in Maragheh or Sararoud.
