Effects of irrigation intervals and different nitrogen fertilizer rates on yield, yield components, essential oil and essence of pot marigold (Calendula officinalis L.)

Introduction Calendula (Calendula officinalis L.) which contains different types of phytochemicals including carbohydrates, fats, phenolic compounds, steroids, tripnoyids, tocopherols, carotenoids and quins that have beneficial effects on human health. Drought stress, caused by soil and atmospheric water deficiency, is one of the most significant environmental factors affecting plant growth and crop productivity in the majority of agricultural fields of the world. Nitrogen is one of the elements which its deficiency is noticeable in arid. semi-arid regions; because the amounts of organic matter which are the main source of nitrogen storage are very low in this region and in case of its existence, it decomposes immediately (Mengel, 2001). Nitrogen’s less or more availability to the plant causes some disorders in crop vital processes that may appear in the forms of abnormal growth and development, decrease in transpiration and even stunt in reproductive growth (Breemhaar, 1995). The purpose of this investigation was study effects of irrigation regims and nitrogen on yield and yield components, essential oil medicinal plant Calendula. Material and Methods In order to study effects of irrigation regimes and nitrogen on yield and yield components, essence oil medicinal plant Calendula an experiment was conducted at Urmia Agricultural Station of Saat Lo at 2016 crop season. Field experiment was carried out by a split plot design based on completely randomized block design with three replications. Treatments were four levels of irrigation levels (irrigation after 5, 10, 15 and 20 day) in main plots, and consumption of 0, 80, 160 and 240 kg/h nitrogen in sub plots. In this study, traits of number of heads per square meter, number of seeds per head, thousand kernel weight, biological yield, grain yield, oil percentage, oil yield and dry flower yield and flower essence were measured. Statistical analysis was performed based on the statistical model of the design used by SAS 9.2 software. Comparison of meanings of each trait was performed using SNK test at 5% probability level. Result and Discussion Analysis of variance showed that irrigation levels had significant effect on all understudied traits also there were significant differences between nitrogen fertilizer levels on all traits except of thousand kernel weight. Also the effect of irrigation levels × nitrogen levels on number of seeds per head, grain yield, oil percentage, oil yield and essential oil percentage were significant. Result showed, with increasing irrigation interval from 5 to 20 days, the number of heads per square meter, number of seeds per head, thousand kernel weight, grain yield, oil percentage, oil yield and dry flower yield decreased, and irrigation levels after 5 and 10 days were the highest values of the mentioned traits. In this research, irrigation level after 10 days had the highest number of seeds per head (22.91 grain), thousand kernel weight (11.19 g), dry flower yield (598.44 kg/h). Result revealed nitrogen fertilizer had positive effect on calendula growth characteristics Although the highest amount of number of seeds per head (22.25), thousand kernel weight (10.52 g) and dry flower yield (575.12 kg/h) belonged to level of 180 kg/h nitrogen fertilizer. Among irrigation levels × nitrogen levels interaction treatments the highest value of number of seeds per head, (24.43), grain yield (1133.3 kg/h), oil yield (356.3 kg/h) and essence percentage (25%) was belonged to 10 days with 80 kg/h nitrogen fertilizer. Conclusion According to the results of this study, it can be stated that nitrogen fertilizer application is effective when sufficient water is available to the plant, and increasing nitrogen levels when there wasn’t enough could have harmful effect on grain yield, oil percentage, oil yield and dry flower yield, oil percentage and flower essence in Calendula. Considering the limitations of water in the area as well as preventing environmental problems, irrigation intervals after 10 days and consumption of 80 kg nitrogen fertilizer in the region to achieve maximum qualitative and quantitative qualities in Calendula is recommended.