Zinc Fractions of Selected Calcareous Soils of Tehran Province, Iran and Their Relations with Soil Properties.
Adil Reyhani Tabar, Najaf Ali Karimian, Mohamad Ardalan, and Gholam Reza Savaghebi. Univ of Tehran, Karaj, Iran
Knowledge about forms of zinc (Zn) is important in the evaluation of soil Zn status and also in understanding soil fertility and chemistry. Amounts and distribution of Zn in different organic and inorganic fractions were examined in 20 soil samples of Tehran province, Iran. Soils were sequentially extracted to determine Zn fractions. Total Zn of soils ranged from 70 to 169.9 mg kg-1. Light-textured soils contained lower total Zn than heavy-textured soils (90 vs 127.44 mg kg-1). The amount of different Zn forms relative to total Zn was determined to be as follows: organic less than 0.1, soluble+exchangeable 0.1, manganese-oxide-associated 1.0, carbonate 1.07, crystalline iron-oxide-associated 3.93, amorphous iron-oxide-associated 4.2, and residual form 89.3%. Simple correlation coefficients showed that pH had a negative significant correlation with all forms of Zn except organic. Clay content had a significant positive correlation with total, residual, and crystalline iron-oxide-asociated Zn but CEC had no significant correlation with any of the Zn forms.Calcium carbonate equivalent % showed a significant correlation with soluble + exchangeable, manganese-oxide-associated and amorphous iron-oxide-associated Zn. A significant correlation was also observed between Zn forms, themselves, which is presumably a reflection of the existence of a dynamic relation between the chemical forms of an element in soil. DTPA-extractable Zn was significantly correlated with soluble+exchangeable carbonate, and amorphous iron-oxide-associated Zn. Key Words: Zn forms, calcareous soils, sequential extraction, soils of Tehran province.