Abstract

Studies on soils developed on volcanic materials in Turkey in light of the wide distribution of these soils and soils defined as Andisols in the Soil taxonomy have not yet been recognized in Turkey. The aims of this study were to: i) show whether some Turkish soils developed in volcanic parent materials found on Mt. Karadag (Karaman Turkey) are Andisols and; ii) investigate their pedogenetic development. For this purpose, 3 representative soil profiles were evaluated. The results revealed that the amount of sand and coarse silt fractions were higher than 30% in all profiles. The bulk density is higher than 0.90 g.cm^-3 in all profiles, while phosphate retention is low (< 20%). Phosphate retention is lower than 85% in all soils studied. Meanwhile, Al + ½ Fe percentages (by ammonium oxalate) are lower than 2% in all profiles. pH values in NaF are lower than 9.5 in the soils studied. Selective extraction of soil samples in all horizons yielded the following trends: ^Fe_d > Fe_p > Fe_o (in profile 1) and Fe_d > Fe_o > Fe_p (in profiles 2 and 3) and, in most horizons Al_p > Al_o > Al_d. According to selective dissolution analysis, non-crystalline minerals like allophane and imogolite were not found. The only non-crystalline minerals found in great quantities were Al-humus complexes and in small quantities ferrihydrite. The semiarid climate and long and dry summer season of volcanic areas, a low rate of weathering, inadequate Si leaching as a result of low precipitation and also very small amount volcanic glass content of parent materials of studied soils prevents andic soil properties. The major factors determining soil genesis on Mt. Karadag would appear to be climate, by affected leaching regime and weathering rates and the volcanic glass content of the parent material.

Key words: Karadag mountain, soil formation, andisols, volcanic material, selective dissolution analysis.