Major Soil Types

This chapter presents the genesis, characteristics, classification, distribution, and land uses of the 10 soil grade groups (Human-made soils, Organic soils, Andosols, Podzols, Fluvic soils, Red-Yellow soils, Stagnic soils, Eutrosols, Brown Forest soils, and Regosols) in the Soil Classification System of Japan. Human-made soils are referred to soils formed through an anthropogenic process, especially in anthropized areas such as urban, industrial, traffic, mining, and waste disposal areas. Organic soils are formed under wetland conditions where the rate of organic matter production exceeds the rate of organic matter decomposition. Andosols are mainly derived from volcanic ejecta or tephra and form during a long period of pedogenetic soil formation process have unique and distinctive properties among soils, such as their fluffy and light surface properties, high humus content, and very high phosphorus-fixing capacity. Podzols are characterized by the eluviation of aluminum (Al) and iron (Fe) from the albic E horizon and their illuviation in the spodic B (Bs) horizon. Fluvic soils are young soils developed from recent alluvial deposits. Red-Yellow soils are a red or yellow color, low accumulation of organic matter, low base saturation, and strong weathering. Stagnogley soils are distributed in terraces, hills, and mountainous areas having a shallow groundwater table. Eutrosols are characterized by high base saturation, that is, with a eutric condition. Brown Forest soils are relatively young soils, are widely distributed in a rather wide range of temperate, and warm temperate zones in humid (high precipitation) climates without fresh volcanic ash deposition. Regosols are very weak weathering soils, which are divided into four groups: Volcanogenous Regosols, Sandy Regosols, Lithosols, and Terrestrial Regosols.