Effects of Irrigation Regimes and Planting Times on Essential Oil Percentage, Yield and Yield Components of Cumin (Cuminum cyminum L.) as a Medicinal Plant

Since ancient times, medicinal plants and aromatic herbs have been used by humans to treat diseases and as spices. Cumin (Cuminum cyminum L.) is the dried seed of the herb, a member of the Asteraceae family. Cumin has a long history of use as food flavors, perfumes and medicine. It is an annual herbaceous plant, with a slender, glabrous, branched stem. The cumin plant grows to 30–50 cm tall and is harvested by hand. Its essential oil is used for bactericidal applications, giving smell to some medicines, sterilizing of surgical operation fiber and producing some veterinary and agricultural medicines. In semi-arid area such as Iran, water is the most limiting factor for agriculture. Cumin has a potential to be as a rainfed plant, but supplemental irrigation is needed to produce more productivity. Little information is available about its consumptive use of water. Also, selecting an optimum plant density is necessary for maximum utility of existing environmental parameters (including water, air, light and soil). As a result, inter specific or intra specific competition is minimum. Thus, many researches has been done to determine the best level of irrigation and plant density and their effects on vegetative and generative parameters of agricultural and medicinal plants. In this paper we aimed to study the effects of different planting dates and irrigation regimes on seed yield and essential oil yield of cumin as an important medicinal plant under the climatic conditions of Torbat-e Jam climatic conditions, Iran. In order to study irrigation regimes and planting dates, an experiment was conducted as split plot based on a randomized complete block design with three replications at the Agricultural Research Station, Azad University of Birjand during growing season 2016-2017. Treatments included four planting dates as main plot (25th November, 27th December, 19th February and 19th March) and four irrigation regimes as sub plot (full irrigation, two times irrigation at vegetative stage (stem elongation), two times irrigation at flowering stage and two times irrigation at seed formation). Plant weight, seed weight, number of branches per plant, number of umbels per plant, number of seeds per plant, 1000- seed weight, seed yield, biological yield, essential oil content and harvest index The treatments were run as an analysis of variance (ANOVA) to determine if significant differences existed among treatments means. Multiple comparison tests were conducted for significant effects using the Duncan’s test. The results showed that the interaction effect of planting dates and irrigation regimes were significant on number of branches per plant, seed yield and biological yield. The simple effect of planting date was significant on number of seeds per umbel, plant height, essential oil percentage, 1000-seed weight and harvest index. The highest seed yield and biological yield were observed in planting at 27th December + full irrigation. The results for correlation coefficients between yield and yield components revealed that there was a positive and significant correlation between these criteria. The highest coefficient was calculated for seed yield and biological yield (r=0.95). Agronomic management strategies had significantly effect on growth, yield, and yield components of cumin. In conclusion, according to the results, full irrigation combined with planting at 27th December could produce optimum seed yield and biological yield in cumin under semi arid climatic conditions. Generally, irrigation regimes and planting date are two safe and effective technique for agronomic management that may decrease the necessity for chemical approaches to crop. On the whole, results of this study revealed that early sowing was more successful, evident from relatively high yields. Considering water shortages that the world will face in the future, winter planting in those environments susceptible to water stress conditions will have higher water use efficiency compared to late sowing time.