The effectiveness of foliar applications of different zinc source and urea to increase grain zinc of wheat grown under reduced soil nitrogen supply

Abstract

Nitrogen is important for the enrichment of grain Zn when Zn is foliarly applied. However, decreasing soil N input has become a major issue for environmental protection. A 2-yr field experiment was conducted to evaluate the effectiveness of spraying different Zn sources [ZnSO4 or Zn(Gly)2] combined with or without urea on grain Zn concentration and bioavailability under reduced soil N rates, both in single wheat plantation and winter wheat-summer maize rotation. Results showed that foliar application of Zn(Gly)2 significantly increased grain Zn concentration by 88% under wheat-summer maize rotation and 150% under single wheat plantation. The effectiveness of foliar ZnSO4 application in increasing grain Zn was similar with that of Zn(Gly)2. Adding urea to foliar ZnSO4 or Zn(Gly)2 further increased grain Zn concentration under reduced soil N rates. Grain Zn biavailability increased with the reduction of soil N rates, but decreased after application of foliar Zn fertilizers. Foliar fertilization significantly increased protein, Fe, and Mn concentrations in grain, and the magnitudes of these increases were greater when Zn(Gly) 2 alone or ZnSO 4 plus urea were applied. Simultaneous foliar application of ZnSO4 and urea slightly increased farmer’s net income. These results suggest that foliar application of ZnSO 4 plus urea can be used as efficient and economical fertilization strategies to increase Zn concentration and bioavailability in wheat grain under reduced soil N supply, and consequently minimize Zn deficiency in humans.