Different increases in maize and wheat grain zinc concentrations caused by soil and foliar applications of zinc in Loess Plateau, China

Zinc (Zn) is an essential mineral nutrient for plant and human growth, and dietary Zn deficiency is a worldwide nutritional problem. Using different Zn fertilizer application methods, this study determines the potential of increasing the Zn concentrations of maize and wheat grain to improve the nutritional status of local residents. Field trials were conducted in the Loess Plateau for two growing seasons to investigate the effects of different Zn fertilizer application methods on the grain Zn concentrations of maize and wheat as well as the grain Zn recovery, yield, and iron (Fe) status of grains under rain-fed conditions. Soil and foliar Zn application did not significantly affect the biomass and grain yield of maize and wheat, suggesting that local soils are not Zn deficient. However, foliar Zn application significantly improved the grain Zn concentration of maize by 27% and 37% and of wheat by 28% and 89% during the first and second growing seasons, respectively. The maize grain Fe concentrations during both growing seasons were also enhanced by foliar Zn application. The foliar application of Zn realized higher grain Zn recoveries of 35.2‰ and 42.9‰ in maize as well as 26.4‰ and 32.3‰ in wheat during the first and second growing seasons, respectively, compared with the soil Zn application with a maximum grain Zn recovery of 1.7‰. Hence, in the Loess Plateau in China, foliar Zn application is an economical method of improving the grain Zn concentration in maize and wheat and increasing grain Fe concentration in maize.

► Soil and foliar Zn application did not affect the grain yield of maize and wheat.
► Foliar Zn application significantly improved grain Zn concentration.
► Foliar Zn application realized higher grain Zn recovery than soil Zn application.
► Maize grain Fe concentrations were also enhanced by foliar Zn application.