Zinc in wheat grain as affected by nitrogen fertilization and available soil zinc

Greenhouse and field experiments were conducted to determine the influence of nitrogen (N) fertilization and DTPA-extractable soil zinc (Zn) on Zn concentration in wheat (Triticum aestivum L., cv. Pioneer 2375) grain. Application of zinc sulfate (ZnSO₄) in the range of 0 to 8 mg Zn kg^-1 increased linearly DTPA-extractable Zn in an incubated calcareous soil from 0.3 to 5.0 mg kg^-1. Application of these rates of ZnSO₄ to the same soil under greenhouse conditions increased Zn concentration of wheat grain from 26 to 101 mg kg^-1. The influence of 134 kg urea-N ha^-1 on Zn concentration in wheat grain at eight field sites, with DTPA-extractable soil Zn levels ranging from 0.3 to 4.9 mg kg^-1, was studied. Nitrogen fertilizer increased wheat-grain yields in four of the eight experiments but had little effect on grain-Zn concentration. Grain-Zn concentration ranged from 31 to 45 mg kg^-1 in N-fertilized plots at the various sites and was related (r=0.74*) to DTPA-extractable soil Zn.