The Status of Chemical Forms of Iron and Manganese in Various Orders of Calcareous Soils and Their Relationship with Some Physicochemical and Mineralogical Properties

ABSTRACT

Iron (Fe) and manganese (Mn) are two essential micronutrients for plant growth, which their deficiency has usually been observed in calcareous soils. Herein the chemical fractionation status of Fe and Mn in surface and subsurface soils of 16 pedons under different climatic conditions, as well as their relationship with some chemical and mineralogical properties, was investigated. As results, the residual, carbonate, and organic chemical forms contained the highest to the lowest levels of chemical forms of Fe and Mn, respectively. Quantitative investigation of chemical forms of Fe and Mn in soils with higher degree of development (Alfisols and Mollisols) and wetter climate (xeric moisture regime) showed a higher content of these elements compared to the soils with a lower degree of development (Entisols and Inceptisols) and drier climate (ustic moisture regime). The correlation between different chemical forms of Fe and Mn with some chemical and physical properties revealed that the organic carbon, cation exchange capacity, pH, calcium carbonate equivalent, and percentage of the soil particle size had the highest effects on the chemical forms of Fe and Mn. Besides, the investigation of the correlation between different chemical forms of Fe and Mn with clay minerals indicated a significant positive and negative correlation with 2:1 silicate minerals (smectite and vermiculite) and palygorskite, respectively. In general, the results demonstrated that the variation of soil formation factors such as climate can significantly affect the chemical forms of Fe and Mn micronutrients and the management of soil orders with a low-to-high level of development.

KEYWORDS:

• Climate
• chemical Forms
• micronutrients
• clay Minerals

Acknowledgments

This paper is a part of a research project in the form of a grant (No. 23672), funded by Payame Noor University which is hereby acknowledged and appreciated.