Effects of zinc sulfate foliar spray on yield, yield components and essential oil of coriander (Coriandrum sativum L.) under drought stress

Due to the irrigation water crisis and the necessity of water resources management as well as the positive role of elements such as zinc in reducing the negative effects of drought stress, a field experiment was carried out as split plot based on randomized complete block design with three replications in Cooperative research field of Yashil Bakhar, Ardebil in 2017. In this research, yield and its components and essential oil of coriander (Coriandrum sativum L.) were investigated in reaction to zinc sulfate foliar spray under drought stress conditions. The experimental factors consisted of four levels of irrigation: irrigation after 70, 100, 130 and 160 millimeter evaporation from class A pan, and three levels of zinc sulfate foliar spray: control (water foliar spray) and foliar spray with three (Zn1:3 g ZnSO4/L) and six (Zn2: 6 g ZnSO4/L) per thousand concentrations. Irrigation and zinc sulfate foliar spray treatments were allocated to the main and sub plots, respectively. The results showed that drought stress reduced the number of umbels per plant, seeds per umbel, seeds per plant, and biological and seed yield. Zinc sulfate foliar spray at Zn2 level resulted in a significant increase in the number of umbels per plant (10.7), biological (21.1%) and grain (21.2%) yield. Under drought stress conditions, the percentage of coriander seeds essential oil increased by 49.2%, but the essential oil yield (1.02 kg ha-1) decreased. The essential oil yield was significantly increased by 27.4% with zinc sulfate foliar spray at Zn2 level. There was no statistically significant difference between Zn1 and Zn2 levels of zinc sulfate foliar spray. Therefore, 3 g ZnSo4/L foliar spray in areas with climatic conditions and soil similar to the research site is recommended to improve the yield and essential oil of coriander.