Forage yield, seed, and forage qualitative traits evaluation by determining the optimal forage harvesting stage in dual-purpose cultivation in safflower varieties (Carthamus tinctorius L.)

Safflower (Carthamus tinctorius L.), adapted to arid and semiarid regions, is grown for seed and petal production, but the present study aimed to evaluate the possibility of simultaneous forage and seed production in the autumn and middle types of safflower varieties in dual-purpose cultivation in semiarid areas in the shortfall forage period. An experiment was done based on a randomized complete block design with nine treatments and three replications at the Seed and Plant Improvement Institute, Agriculture Research, Education and Extension Organization, Karaj, Iran. The treatments included the cultivation of Parnian, Goldasht, and Golmehr varieties with the purpose of seed harvesting as control treatments; the same varieties (Parnian, Goldasht, and Golmehr), once with the aim of forage harvesting at 50% stem elongation stage and seed harvesting; and again with the aim of forage harvesting at 50% branching stage and seed harvesting. The results showed that forage harvesting at the 50% branching stage significantly increased the dry and fresh forage yield compared to the 50% stem elongation stage. The highest fresh and dry forage yields (DFY) (42,229 and 11,266 kg/ha) were related to the Golmehr variety at the 50% branching stage. Forage harvesting at the stem elongation stage decreased the crude protein, protein content, and digestibility compared to the branching stage in three safflower varieties. Parnian variety had the maximum seed yield (2,226 kg/ha) without forage harvesting. The highest seed yield in the second year (2018–2019) of the experiment belonged to the Golmehr variety (1,310 kg/ha) to harvest forage at 50% stem elongation (rapid stem growth) and seed harvest treatment, which compared to the first year (2017–2018), showed an increase of 25%. Finally, the forage harvested amount of all three varieties studied was higher in the branching stage than in the stem elongation stage. These results implied that the Golmehr variety (11,266 kg/ha DFY and 520 kg/ha seed yield) is for dual-purpose cultivation, and the Parnian variety (2,226 kg/ha seed yield) is suitable for only seed production for the semiarid region of Karaj in Iran and similar areas in terms of climate.