Effects of humic acid foliar application on the quantitative and qualitative characteristics of cumin (Cuminum cyminum L.) under different irrigation regimes

In order to study the application of humic acid and different irrigation regimes on quantitative and qualitative characteristics of three accession of cumin (Cuminum cyminum L.), an experiment was conducted at the Research Farm of Medicinal Plants, Faculty of Agriculture, Shahed University in 2016. This experiment was a factorial split plot based on randomized complete block design with three replications. Experimental factors included three irrigation regimes (full irrigation, irrigation after flowering stage and irrigation after grain filling stage), foliar application of humic acid with two levels (0 and 200 mg/lit) and three cumin accessions (Esfahan, Kashan and Sabzevar). The results of analysis of variance showed that the interaction effect of irrigation regime*humic acid*accession had significant effect on single plant dry weight, grain yield, harvest index, chlorophyll a and total. The results showed that the highest single plant dry weight and grain yield were obtained in complete irrigation and humic acid application. Kashan accession had the highest branch number per plant, dry weight per plant, number of seeds per umbrella, grain yield and biological yield. The highest percentage of essential oil yield was observed in Sabzevar accession. The highest grain yield (533.3 kg/ha) was obtained in complete irrigation with the use of humic acid in Kashan accession. The highest average dry matter yield (230 kg/ha) was obtained in complete irrigation with the use of humic acid for Sabzevar accession. The highest amount of chlorophyll a and total was observed in irrigation after flowering stage and lack of application of humic acid in Sabzevar accession. The application of humic acid was not significant on the traits evaluated. The most efficiency of humic acid was obtained in full irrigation. According to the results of this experiment, it can be stated that full irrigation and application of humic acid can increase the yield of Kashan accession in similar experimental conditions.