Spraying high concentrations of chelated zinc enhances zinc biofortification in wheat grain

Foliar application of highly concentrated ZnSO₄ fertilizer improves Zn biofortification in wheat grains. However, excess ZnSO₄ ·7H₂ O concentration (≥5 g kg^-1 , w v^-1 ) has been associated with leaf burn and yield loss, necessitating Zn sources with a high threshold concentration. The aim of this study, based on a 2 year field experiment conducted on wheat cultivated in acidic and alkaline soil, was to identify a suitable Zn formulation with a high Zn concentration or efficient adjuvant to achieve optimal Zn biofortification levels without compromising agronomic performance.

There was a continued increase in the Zn concentration in wheat grains and a decrease in grain yield with an increase in the concentration of the Zn foliar sprays in both soil types examined. Wheats treated with chelated Zn foliar sprays - Zn glycine chelate (ZnGly) and Zn-ethylenediaminetetraacetic acid (ZnEDTA) - had less foliar injury than those treated with unchelated Zn fertilizers. Furthermore, irrespective of wheat cultivars and soil types, ZnEDTA applied to wheat at a concentration of 10 g kg^-1 achieved the highest grain Zn concentration without negatively affecting the wheat performance. Adjuvant type and concentration caused no significant variation in grain Zn concentration.

Overall, without foliar burn, wheat treated with 10 g kg^-1 ZnEDTA foliar spray had the best performance with regard to grain Zn concentration and grain yield, which could have considerable implications for Zn biofortification of wheat grain. © 2021 Society of Chemical Industry.