Effect of Climate and Soil Development on the Quantity and Chemical Forms Distribution of Iron, Copper, Zinc and Manganese Micronutrients in the Dominant Soil Orders of Kohgiluyeh and Boyerahmad Province

Determining the relative distribution of each chemical form of the elements and their relationship with the physical, chemical, and clay mineralogical properties of soils can help researchers to achieve the sustainable agricultural management. The present study was conducted to evaluate the chemical forms of four micronutrients (Zn, Cu, Fe and Mn) in some surface and subsurface soils of Kohgiluyeh and Boyer Ahmad province and their relationship with the physical, chemical and mineralogical properties of the soils. The results showed that the exchangeable and sorbed chemical forms of the studied elements were very low and negligible, but the residual, carbonate, and organic forms had the highest to lowest values of the chemical forms of these elements, respectively. Examination of the correlation of the chemical forms of these elements with soil properties showed the effective correlation of organic carbon values with the Zn chemical forms; also, there was a correlation between clay, silt, cation exchange capacity and calcium carbonate and the chemical forms of Cu, Fe and Mn. The correlation between the quantities of clay minerals and the chemical forms of these elements showed that the amounts of different forms of the studied elements were directly related to 2:1 clay silicate minerals (especially vermiculite). Evaluation of Fe and Mn chemical forms  also showed that the amounts of these elements were higher in the  soils with developed profiles (Alfisol and Mollisol), the  wetter climate and zeric moisture regime rather  than in soils with non-developed profiles (Entisols and Inceptisols) and a drier climate and a ustic moisture regime. In general, the results showed that variations of soil forming factors such as climate (as well as the  total amount of each micronutrients), could be effective on the chemical forms of micronutrients (especially on Mn and Fe);  these can be effective in the management of weakly to highly-developed soils orders.