Pinched sunflowers (Helianthus annuus ‘Teddy Bear’) produce high-quality flowers under high nitrogen fertilizer

This study was investigated the effect of removing the central bud (pinching) and different levels of nitrogen fertilizer urea on some morphological and physiological traits of ornamental sunflower. This study was conducted as a factorial experiment in a randomized complete block design with four replications on ornamental sunflower (Helianthus annuus ‘Teddy Bear’) at Horticulture Farm, Department of Horticulture, Ferdowsi University of Mashhad, Iran, in 2020-2021. The first factor was pinching in two levels (pinching and non-pinching) and the second factor was using urea at four levels (0, 200, 300, and 400 kg ha-1) in the form of water-soluble fertilizer. Results showed that the highest flower dry mass (59.25 g) was observed in pinched plants fertilized by 400 kg ha-1 of urea. Besides, the application of a high level of urea fertilizer and pinching treatment increased the amount of total chlorophyll and chlorophyll b. By removing the central bud, the amount of N, P, K, Ca, Zn, and Fe elements in the leaf increased by 1.5, 1.6, 1.3, 1.9, 1.4, and 1.5 times, respectively. Therefore, pinching and the adding of urea fertilizer at 400 kg ha-1is recommended for the production of high-quality sunflower plant ‘Teddy Bear’.