Mitigation of Drought Stress and Yield Improvement in Wheat by Zinc Foliar Spray Relates to Enhanced Water Use Efficiency and Zinc Contents

Water and nutrients scarcity are the two major factors for yield reduction in many wheat-producing areas of the world. Drought stress also restricts micronutrient uptake and thus induces micronutrient deficiency. Zinc is the most important micronutrient for abiotic stress tolerance. A field trial was conducted from 2013 to 2015 to study the effect of foliar application of zinc under normal (100% field capacity) and water deficit (60% field capacity) conditions on quantitative and qualitative aspects of wheat (Triticum aestivum L. var. Faisalabad-08). Three Zn levels (0, 0.1%, and 0.2% by using ZnSO4. 7H2O) were foliar sprayed at the vegetative and reproductive stages of wheat. Obtained results revealed that the growth, yield traits, photosynthetic pigments, and WUE were negatively affected by lower water supply. Zinc foliar application did not affect yield under normal irrigation conditions, however, under water deficit foliar application of 0.2% Zn enhanced grain yield to 25–40%. Zinc foliar spray at both vegetative and reproductive stages increased the chlorophyll contents and WUE. Zinc contents of wheat grain were more when 0.1% Zn was sprayed at the reproductive stage or 0.2% Zn at the vegetative stage. Thus, the foliar application of Zn is a promising short-term approach to improve productivity and grain nutrient content in wheat under water deficit stress. Furthermore, the timing and rate of Zn application could be helpful for the efficient use of water for increasing grain yield.