Soil-zinc application required to improve bread and durum wheat production under cold rainfed conditions

Simultaneous drought stress and zinc (Zn) deficiency can affect plant responses to water scarcity and limit wheat production in rainfed areas of Iran. Zinc-deficient plants have low water use efficiency and they cannot control well osmotic pressure to cope with water stress. In this study, the effects of Zn application and drought stress were investigated on grain yield of 10 wheat varieties (6 bread wheats and 4 durum wheats) grown in a Zn-deficient calcareous soil over 2 cropping seasons under rainfed conditions. Plants were treated with (+Zn: 10 kg Zn/ha, as ZnSO₄.7H₂O) and without Zn (-Zn) in RCBD with 3 replications. Zinc fertilization could enhance biomass, harvest index and grain weight of genotypes that resulted in 9% and 7% grain yield increase on average in the first and second years, respectively. Increases in yield varied among genotypes from 1% to 19%; and durum genotypes showed higher rising. Accordingly, there was variability in Zn efficiency of genotypes (ratio of grain yield under Zn deficiency compared to that under Zn fertilization). The correlation between Zn-efficiency and yield increase of genotypes was positive (r=0.72); however, durum wheat genotypes generally showed low level of Zn efficiency that resulted in lower yield under Zn deficiency especially under drought conditions in the first year. The results presented here demonstrate the existence of variation in Zn efficiency among bread and durum genotypes, and suggest the possibility of breeding for higher yield and Zn efficiency in Zn-deficient soil under rainfed condition. Moreover, Zn application would increase bread and especially durum wheat’s productivity in cold drylands.