Document Type : Research Article
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Abstract
Sewage sludge uses as a low coast fertilizer to rectify deficit of elements such as zinc (Zn). A suitable extractant for estimation of bean-available Zn in calcareous soils amended with sewage sludge has not yet been introduced. The aim of this research was to assess several chemical extractants for the estimate of available Zn in sewage sludge-amended calcareous soils. For amended soils, 1% (w/w) of sewage sludge was added to 10 calcareous soils, and the soils (amended and un-amended) were incubated at field capacity for 30 days. At the end of incubation, soils were air-dried and available Zn was determined using 7 chemical extractants (DTPA-TEA, AB-DTPA, Mehlich 1, Mehlich 2, Mehlich 3, 0.1 N HCl and 0.01 M CaCl2). Zinc concentration in shoots, Zn uptake, and shoot dry weight of bean were determined in a pot experiment in amended and un-amended soils. The results show that Mehlich 3 and Mehlich 1 extractants extracted the highest and the lowest concentrations of Zn in both amended and un-amended soils, respectively. Furthermore, all three studied indices and Zn extracted by using different methods increased in amended soils. In addition, results indicated that significant correlations were found between extracted Zn using AB-DTPA, DTPA-TEA and Mehlich 3 and plant indices in un-amended soils. On the contrary, in sewage sludge-amended soils only the correlation between extracted Zn using DTPA-TEA and Mehlich 1 with Zn uptake and shoot dry weight and Mehlich 2 with Zn concentration was significant. The results of this study showed that DTPA-TEA could estimate bean-available Zn in the sewage sludge-amended and –un-amended calcareous soils.
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