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The different landscape positions, the type of parent material and its formation processes, and the soil type significantly impact the distribution, behavior, and mobility of micronutrients. To investigate the effects of landscape and soil types on the distribution and behavior of micronutrient elements of iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn), some genetic horizons samples were collected from sixteen representative pedons in the calcareous soils of southwestern Iran. Subsequently, the concentrations of extractable trace elements were assessed using diethylene triamine pentaacetic acid (DTPA) as well as in their total form through digestion in concentrated nitric acid. The results showed that the change range in the available form of studied micronutrients varied between 2.5 to 31.2, 0.3 to 3, 2.1 to 60.2, and 0 to 3.8 mg kg-1 for Fe, Cu, Mn, and Zn respectively. The examination of the chemical forms of micronutrients in both surface and subsurface samples unveiled that the majority of the investigated chemical forms exhibited higher quantitative levels in the surface samples compared to the subsurface samples. v(%CaCO3) of the soil increased when the soil moisture regime largely depends on the percentage of organic carbon (% OC) content, soil texture, and type and content of clay minerals. The highest amounts of available micronutrient elements were found in Mollisols and Alfisols soil orders. Additionally, the highest available form of Cu, Zn, and Fe were found in lowland soil units (LL), while Mn was detected in piedmont plains (PP) landform. Consequently, it can be inferred that the cycling of micronutrients is influenced by varying levels of soil development, which in turn impact the properties of the soil. [ABSTRACT FROM AUTHOR]

Changing land use from rangeland and forest to agricultural land and orchard can greatly affect the characteristics and fertility of the soil, especially in arid and semi-arid regions. In this study, seven major land-use types in Kohgiluyeh-and-Boyer-Ahmad province of southwest Iran were selected; these land types were orchards (grape), forests, rangelands, and agricultural lands which cultivated corn, beans, and rainfed and irrigated wheat containing five soil orders, namely Entisols, Inceptisols, Mollisols, Alfisols, and Vertisols. The samples were collected from the soil depths of 0-30 cm. Based on the results, the highest average content of organic carbon (OC) was detected in the forest (3.3%). It may thus be stated that there is a balance in forest soils between the rapid decomposition of soil organic matter and the rapid accumulation of litter due to plantation and also an abundance of litter. In all soil samples, the highest percentage of Fe and Mn were found in the residual (Res) fraction and the lowest percentage in the exchangeable (Ex) fraction. The highest and lowest amounts of Fe and Mn carbonate (Car) form were associated with forest and rangeland land uses. Different land uses had an important influence on the amount of the Fe form bound to organic compounds. In this way, the maximum amount of this form belonged to forest use which contained the highest amount of organic matter; the lowest amount of organic matter was related to rangeland use. [ABSTRACT FROM AUTHOR]