Study on humic acid and algae effects on grain yield and agronomical characteristics of cumin (Cuminum cyminum L.) under drought stress conditions

Cumin (Cuminum cyminum L.) is one of the valuable medicinal plants cultivated in arid and semi-arid regions of Iran, facing to drought stress. Accordingly, an experiment was conducted to investigate the effects of algae extract and humic acid on cumin under drought stress conditions as a factorial split plot in a randomized complete blocks design with three replications in a farm located in Boyer-Ahmad city, 35 km from Yasouj, Kohgiluyeh and Boyer-Ahmad province in 2019 and 2020 years. The experimental factors included drought stress as the main factor at three levels of irrigation after consumption of 35 (control), 70, and 90% of soil moisture and humic acid at two levels of 0 and 300 mg.L-1 and algae at two levels of 0 and 2 L.ha-1 as the sub-factors. The results showed that foliar application of humic acid and algae extract had a significant effect on essential oil yield, number of branches, biological yield, grain yield, 1000-seed weight, number of seeds per umbrella, number of umbrellas per plant, plant height, and essential oil percentage and improved the negative effects of drought stress. The highest grain yield, 1000-grain weight, essential oil yield, and number of grains per umbrella were obtained by foliar application of humic acid and algae extract. The application of humic acid was more effective than algae extract on traits except yield and essential oil percentage which were more affected by algae extract. In general, the results showed that foliar application of humic acid and algae extract could moderate the adverse stress conditions and increase cumin yield by 41.4%.