Effects of soil and foliar applications of Zn on winter wheat grain Zn concentration and bioavailability

A field experiment with a split plot design was conducted to investigate the effects of different Zn application methods (soil application or foliar spray) on grain Zn concentration and Zn bioavailability of 5 winter wheat cultivars in potentially zinc (Zn)-deficient calcareous soil. The results show that there are little effects of applying Zn fertilizer on grain yield of wheat, while the grain Zn concentration is significantly increased under certain methods of Zn application. Compared with the control treatment (no Zn application), the grain Zn concentrations are increased by -6.1%, 63.9% and 82.6% under the methods of soil application, foliar spray and soil+foliar application of Zn fertilizers, and the grain Zn uptakes are increased by -3.6%, 69% and 83%, respectively. The phytic acid concentrations are decreased by -2.4%, 7.2% and 1.5% and the phytic acids to Zn molar ratios are decreased by -25%, 41% and 44% of the three treatments, respectively, and there are differences of the phytic acid concentration and the ratio among wheat cultivars. Although the molar ratios of phytic acid to Zn are decreased by the Zn applications, the ratios are still higher than 20. The soil application of Zn can increase the content of soil DTPA-Zn significantly, while the effects of the soil application of Zn on grain Zn concentration and bioavailability are not significant. In conclusion, comparing with the 3 Zn application methods, the foliar application of Zn fertilizer to wheat at the late growth stage (for example, the milk and dough stage) is an economical and effective method to attain high Zn concentration and bioavailability, and to improve the Zn quality of wheat grain in potentially Zn-deficiency calcareous soil.