Improvement of yield, oil and protein percentage of sesame )Sesamum indicum L.) under drought stress by foliar application of zinc and boron

Background and objectives: Drought stress is one of the most important environmental factors reducing growth and yield of crops, especially in arid and semiarid regions of the world. During drought stress, nutrient uptake diminishes due to rising of solute concentrations and so increasing of osmotic potential in the root zone. With increasing soil pH, micronutrient uptake decreases more than other nutrients. Zinc and boron deficiencies are mostly observed in these conditions, so that yield quantity and quality of oilseed crops, such as sesame, diminish even without any apparent deficiency symptoms. The aim of this study was to determine the effect of foliar application of zinc and boron on sesame yield, yield components and seed oil and protein contents under drought stress conditions.
Materials and methods: The experiment was conducted as a spilt pilot in a randomized complete block design with three replications at Fars research center for agriculture and natural resources in 2013. Main plots were included of three levels of drought stress (as irrigation after 75, 110 and 145 mm evaporation from class A evaporation pan) and sub plots were included of four levels of foliar applications (no boron and zinc (water), zinc sulfate, boric acid, and combined zinc and boric acid).
Results: Results showed that zinc and boron foliar application significantly increased number of capsule per plant in 75 mm evaporation treatment. Zinc also increased number of capsule per plant in 145 mm evaporation treatment. Maximum 1000 seed weight obtained from boron foliar application in irrigation after 145 mm evaporation treatment. In irrigation after 110 mm evaporation level number of seed per capsule significantly increased (25.4%) with foliar application of mixture of zinc and boron compared to control. Irrigation after 145 mm evaporation (relative to two other treatments) had the minimum seed yield (1535 kg ha-1), But there were no significant difference beween irrigation after 75 (1947 kg ha-1) and110 (2115 kg ha-1) mm evaporation. Foliar application of zinc and boron (compared to control) significantly increased oil percentage and foliar application of zinc, boron and mixture of zinc and boron (compared to control) significantly increased protein percentage. Maximum seed yield (2119 Kg ha-1) obtained from foliar application of zinc. Irrigation after 145 mm evaporation, compared to other irrigation treatments, significantly decreased HI.
Conclusion: Generally foliar application of zinc, boron and mixture of zinc and boron under drought stress treatment, could improve yield, yield components, oil and protein percentage of sesame.