Zn distribution and bioavailability in whole grain and grain fractions of winter wheat as affected by applications of soil N and foliar Zn combined with N or P

• A trivariate model of Zn absorption is used to evaluate Zn bioavailability.
• Phytate concentration decreases after soil or foliar N-enriched application.
• Foliarly supplied Zn and N are synergistically effective on Zn bioavailability.
• Foliar Zn plus P application produces a negative effect on Zn bioavailability.
• Most Zn is allocated in flour and its distribution ratio is not changed.

A two-year field experiment was conducted to investigate the effects of foliar Zn combined with N or P on Zn concentration and bioavailability in wheat grain and its milling fractions under different soil N levels. At maturity, grains were harvested and fractionated into flour and bran for nutrient analysis. Both high soil N supply and foliar Zn-enriched fertilizer applications greatly increased Zn concentration and bioavailability in both whole grain and grain fractions. Compared with foliar Zn alone, foliar Zn combined with N increased Zn concentration and bioavailability, whereas foliar Zn combined with P decreased Zn concentration and bioavailability. However, foliar Zn combined with P slightly increased the protein concentration compared to foliar Zn alone. Protein concentration significantly increased, whereas phytate concentration decreased, in whole grain and flour, both in soil N and foliar Zn-enriched N treatments. Therefore, foliar Zn plus N (with appropriate soil N management) may be a promising strategy for addressing dietary Zn micronutrient deficiencies, especially in countries where flour is a significant component of the daily diet.