Saturday, 15 July 2006

Classification of Heugag Soils in Jeju Island.

Kwan-Cheol SONG, National Institute of Agricultural Sciences and Technology, #249 Se-Dun Dong KewonSun Gu, Su-Won, 441-707, South Korea

Jeju Island is volanic island, and is located about 96km south of Korean Peninsula. Volcanic ash is widespread as a soil parent material throughout island. Soils on the island have the characteristics typical volcanic ash soils. This study was conducted to classify Heugag soils, widely distributed on high elevated mountainous region in Jeju Island according to Soil Taxonomy. For this study, morphological properties of typifying pedon of Heugag soils were investigated, and physio-chemical properties were analyzed according to Soil Survey Lavoratory Methods Manual. Heugag soils have thin very dark grayish brown (10YR 3/2) stony to bouldry silt loam A horizons(0-10cm) and dark grayish brown(10YR 4/2) stony silt loam AB horizons(10-40cm). B horizons(40-100cm) are brown to dark brown(10YR 3/4) stony loam. They occur on high elevated mountainous region derived from volcanic ash materials. A, BA, and B horizons of Heugag soils contain 5.2-9.8% oxalate extractable (Al + 1/2Fe), over 85% phosphate retention, and lower bulk density than 0.90 Mg/m3. A, BA, and B horizons of Heugag soils have andic soil properties. Heugag soils can be classified as Andisols. Heugag soils have an udic soil moisture regime and have a 1,500kPa water retention of 15% or more on air-dried samples throughout all horizons, and can be classified as Udands. A, BA, and B horizons of Heugag soils meet the depth, thickness, and organic carbon requirements for a melanic epipedon, but do not meet color requirement for a melanic epipedon Therefore, Heugag soils key out as Fulvudands. Heugag soils have extractable bases(by NH4OAc) plus 1N-KCl extractable Al totaling less than 2 cmol(+)/kg in the fine-earth fraction in B horizons with a total thickness of 30cm or more. 1,500kPa water retention on air-dried samples is less than 70% throughout all horizons. Thus, Heugag soils key out as Acrudoxic Fulvudands. Heugag soils have a fine-earth fraction that has a water content at 1,500kPa tension of 12% or more on air-dried samples; and have less than 35%(by volume) rock fragments. Thus, their substitute for particle-size class are medial. Heugag soils can be classified as medial, mesic famly of Acrudoxic Fulvudands. Key words : andic soil properties, Allophane, Ferrihydrite, Acrudoxic Fulvudands

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