In determining the best level of humic acid foliar application and suitable plant density and their effect on growth traits, yield components, and the quality of three safflower (C. tinctorius L.) cultivars, an experiment commenced during the winter crop season of 2019–2020 at two locations. The first location was Zmmaar Village, Mosul City, and the second location was in the Sallamiya Region, south of Mosul City, Iraq. The experiments had a randomized complete block design (RCBD) layout with factorial arrangement and three replications. Each experiment included three levels of humic acid (HA1: 0, HA2: 4, and HA3: 8 mg L-1) with three plant densities (PD1: 46,296, PD2: 69,444, and PD3: 138,888 plants ha-1) and three safflower cultivars (C1: Goldasht, C2: Oleic Leed, and C3: Aswan). The safflower with a humic acid concentration of 8 mg L-1 resulted in a significant increase in growth, yield, and quality traits compared with the lowest concentration (4 mg L-1) and the control treatment in both locations. Plant density (46296 plants ha-1) was superior by giving the highest seed yield per plant, biological yield, harvest index, oleic and linoleic acid, and oil and protein percentages for both locations. The safflower cultivar Aswan achieved the highest rate of growth, productivity, and quality traits compared with cultivars Oleic Leed and Goldasht at both locations.
Safflower (C. tinctorius L.) cultivars, humic acid, plant density, seed yield, biological yield, harvest index, oleic and linoleic acid, oil and protein percentage
The safflower (C. tinctorius L.) cultivars with humic acid foliar application (8 ml L-1) resulted in a significant increase in growth, yield, and quality traits compared with the lowest concentration (4 ml L-1) and the control treatment in both locations.