Effect of Soil and Foliar Zinc Application on Zinc Concentration and Bioavailability in Wheat Grain Grown on Potentially Zinc-deficient Soil

Three field experiments were conducted to determine the effect of soil Zn, foliar Zn, and soil N application on Zn and phytic acid concentrations in wheat grain grown on potentially Zn-deficient soil. Results showed significant genotypic variation in grain Zn concentrations among fifteen wheat cultivars commonly grown in northwest China. Soil Zn application had mixed effects, increasing grain Zn concentrations of some cultivars by as much as 21%, but reducing grain Zn concentrations of other cultivars by as much as 14%. In comparison, foliar Zn application increased grain Zn concentrations by 26 to 115%. Grain Zn concentrations were 14% larger in the combined (foliar Zn + soil Zn) treatment compared to the foliar Zn treatment, but the added cost of soil Zn application may not be economically justifiable. Wheat grain phytic acid concentrations and phytic acid: Zn molar ratios were less in the foliar Zn and (foliar Zn + soil Zn) treatments compared to the soil Zn and the unfertilized treatments. This indicated that foliar Zn increased Zn bioavailability. Best results were obtained when foliar Zn was applied at early grain filling. Overall, these findings indicate that foliar Zn application to Zn-efficient cultivars could reduce human Zn deficiency in regions with potentially Zn-deficient soil.