Characteristics of Volcanic Ash Soils

화산회토(火山灰土)의 특성(特性)에 관(關)하여

Volcanic Ash Soils are widely distributed in Jeju island, and constitute the important upland soils which are either presently being cultivated or are suitable for reclaiming. The characteristics of Volcanic Ash Soils according to data made available by previous studies in Jeju and the outside of the country are as following: The most conspicuous mineralogical property is the presence of amorphous mineral colloids. The colloids have large and highly reactive surface to which the common physical and chemical properties are related. Soils are low in bulk density and higher both in porosity and permeability. Accumulation of humus in the upper part of soil is found in great quantity. Cation exchange capacity is high mainly due to high humus content, but the absorbing intensity of ammonium and potassium is weaker than that of crystalline clays. The phosphate absorption coefficient is extremely high and deficiency of minor element may occur both crops and animals. Soils are densely populated with actinomycetes and anaerobic bacteria. Nitrification and activity of urease are distinctly stronger than that of non-Volcanic Ash Soils.