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DISTRIBUTION AND PHYTOAVAILABILITY PREDICTION OF ZINC IN AGRICULTURAL CALCAREOUS SOILS

The extractability and distributions of zinc (Zn) were evaluated in calcareous agricultural soils from South-West Iran. Both single [diethylenetriaminepentaacetic acid (DTPA)] and sequential extraction procedures (Singh scheme) were applied to 20 representative soils. The DTPA extractable zinc levels were low (on average 3.34%). The sequential extraction procedures were also utilized for the study of zinc phytoavailability in maize plants (Zea mays L.) in a greenhouse experiment. The Singh scheme was significantly better than DTPA plus soil properties in phytoavailability prediction of zinc in soils. Significant correlations were found between the amounts of DTPA extractable zinc and the iron (Fe) oxides-bound (AFe and CFe) and residual fractions extracted by the Singh procedure. Zinc concentrations in plant samples (mean value of 27.49 mg kg−1) were poorly correlated with the different extracted soil fractions (single and sequential). The Singh procedure provided better predictions of zinc uptake by plants than DTPA extraction method.