Assessment of Several Extractants for the Determination of Wheat-available Zn (Triticum aestivum L.) in Calcareous Soils Amended and Unamended with Sewage Sludge

Zinc (Zn) is one of the essential micronutrients for plant growth and its deficiency frequently occurs in calcareous soils. But, a suitable extractant for estimation of plant-available Zn in calcareous soils, amended with sewage sludge, has not been presented yet. The aim of this research was to assess several chemical extractants (7 extractants) for estimation of available Zn in calcareous soils amended (1% w/w) and unamended with sewage sludge. Results showed that Mehlich 3 and Mehlich 1 extractants extracted the highest and the lowest concentrations of Zn in both amended and unamended soils, respectively. All wheat indices (wheat yield, Zn concentration and Zn uptake) increased by sewage sludge addition. Besides, the results indicated that in unamended soils, significant correlations were found (r=0.65*- 0.91**) between extracted Zn using AB-DTPA, DTPA-TEA and Mehlich 3 extractants and different wheat indices. On the contrary, in sewage sludge-amended soils, only the correlation between extracted Zn using Mehlich 2 and Zn concentration was significant (r=0.83**). According to this study findings, the suitable extractant for extracting wheat-available Zn is thoroughly different in calcareous soils amended and unamended with sewage sludge.