Soil formation overlying volcanic materials at Mount Erenler, Konya, Turkey

Authors: SIDIKA ÖZCAN, HASAN HÜSEYİN ÖZAYTEKİN

Abstract: Studies of soils developed on volcanic materials are insufficient in Turkey in light of the wide distribution of these soils. The objectives of the present work were to assess the influence of climate and other soil-forming factors on physical, chemical, and mineralogical characteristics and pedological processes in the soil genesis and soil classification of 4 volcanic soil profiles derived from andesitic parent material, and to determine whether they meet the requirements for classification as Andisols. Collected from a semiarid climate in Konya, Turkey, these soils are characterized as medium- and fine-textured with low organic matter content, low cation exchange capacity, and low soil moisture retention. Bulk density was greater than 0.90 g cm^{-3} in all profiles. In general, phosphate retention was low, and lower than 85% in all profiles. The Al + ½ Fe percentages (by ammonium oxalate) were lower than 2% in all profiles. The pH values in NaF were less than 9.5 in the soils studied. Selective extraction yielded the following relationship in all extractions: Fe_d > Fe_o > Fe_p. Additionally, in most horizons: Al_p > Al_o > Al_d. According to selective dissolution analysis results and index values, noncrystalline minerals such as allophane, imogolite, and iron-humus complexes have not formed in these soils. Only noncrystalline minerals were present, such as Al-humus complexes in great quantities, and, in small quantities, ferrihydrite. Crystallized Fe minerals were more common than other Fe minerals. Feldspar, cristobalite, and quartz were the most common primer minerals. Hematite, cummingtonite, and magnetite were also found in some profiles. X-ray diffraction indicated that kaolinite and illite were dominant minerals in the clay fraction; furthermore, a considerable amount of smectite was found in the clay fraction. The local climate, characterized by low precipitation and a long dry season, obstructs the formation of andic soil properties because of the low rate of weathering and inadequate Si leaching. As a result, the soils of Mount Erenler were not classified as Andisol but rather as Entisol. The major factors determining soil genesis on Mount Erenler appear to be climate, topography, and the nature of the parent material

Keywords: Soil formation, soil classification, volcanic material, Mount Erenler, Konya

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