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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).

The objective of this 4-year study was to determine single and repetitive effects of sewage sludge applications on the accumulation of lead (Pb), cadmium (Cd), zinc (Zn) and copper (Cu) in soil and wheat (Triticum aestivum). A single sludge application at a rate of 100 Mg ha -1 (for all the metals) and at a rate of 50 Mg ha -1 (for Cu) significantly increased DTPA-extractable metal concentrations 4 years later. DTPA-extractable concentrations of Pb, Zn and Cu were closely correlated with the total concentrations in soil. Their relationships between metal uptake in stalks and DTPA-extractable metal concentrations in soil were approximately linear for Pb, Cd and Cu, but better described by a quadratic equation for Cd and Zn. TF for Pb, Zn and Cu, BF for all metals and BCF for Pb, Cd and Zn were lower in wheat grown on sludge-treated than control plots.

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