Comparison of Several Chemical Extracts for the Determination of Zinc Bioavailability to Sunflower in Heavy Metal-Contaminated Calcareous Soils

Zinc is one of the essential micronutrients for plant growth and its deficit is often reported in calcareous soils. The total amount of soil Zn does not necessarily indicate Zn availability for plant. Therefore, finding an appropriate extractant, in order to estimate plant available Zn in soil is important. Considering that little information in Iran is available regarding available Zn, in heavy metals contaminated calcareous soils, therefore, assessment of status of available Zn for plants by chemical extractants is very important and necessary. The aim of this research was to assess extraction methods Mehlich 3, AB-DTPA and DTPA-TEA to estimate the sunflower available Zn in 9 contaminated soils. Sunflower plant parameters including dry matter, concentration, and Zn uptake were determined in a pot experiment. The results showed that in contaminated soils, the highest concentration of Zn by use of AB-DTPA and the lowest concentration of Zn by use of DTPA-TEA were extracted. Moreover, in contaminated soils significant correlation wasfound between extracted Zn by DTPA-TEA with concentration and Zn uptake (r=0.78). There were significant correlations between extracted Zn by Mehlich 3 with concentration (r=0.68) and Zn uptake by plant (r=0.80). Thus, it can be concluded that DTPA-TEA and Mehlich 3 methodes can be used to estimate the ability of sunflower-available Zn in contaminated soils