Grain zinc, iron, and copper concentrations of wheat grown in central iran and their relationships with soil and climate variables.

We performed a survey in central Iran to assess the variability in grain zinc (Zn), iron (Fe), and copper (Cu) concentrations of winter wheat and their relationships with soil and climate variables under field conditions. The goal was to identify factors that should be studied further to improve wheat cultivation in the study area with respect to the nutritional quality of this main Iranian staple crop. Soil and grain samples were collected from 137 randomly selected wheat fields in the provinces of Qom, Isfahan, and Fars. In general, soils were characterized by a high pH. Grain micronutrient concentrations ranged from 11.7 to 64.0 mg kg(-1) (mean, 31.6 mg kg(-1)) for Zn, from 21.1 to 96.6 mg kg(-1) (mean, 42.7 mg kg(-1)) for Fe, and from 2.4 to 9.3 mg kg(-1) (mean, 5.5 mg kg(-1)) for Cu. The grain concentrations of these three metals were positively correlated to each other. DTPA-extractable and total soil micronutrient concentrations alone were very poor predictors of grain micronutrient concentrations. Predictions were slightly improved when other soil and climate variables were taken into account (Zn, R2=0.26; Fe, R2=0.08; and Cu, R2=0.13).