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Soil formation process (土壌形成過程)

Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily

soil formation = soil evolution

Weathering (風化)

= rock weathering

  1. physical (mechanical) weathering
  2. chemical weatehring
  3. biological weathering
Four processes of soil formation

addition (添加) of material to the developing soil profile from outside sources, such as organic matter from leaves, dust from the atmosphere, or soluble salts from groundwater

loss (損失) of material from the soil profile by leaching to groundwater, erosion of surface material, or other forms of removal (often transformation and translocation result in the accumulation of material in a particular horizon)


translocation (移動) or transportation of inorganic and organic materials from one horizon to another, either up or down (material is primarily moved by water but may also be moved by soil organisms)

transformation (物質変化) of soil constituents from one form to another, such as through mineral weathering and organic matter breakdown

factors on soil formation (土壌形成要因)

rhizosphere (根圏): soil that is directly influenced by root secretions and associated microorganisms

endorhizosphere (内根圏)
rhizoplane (根面)
exorhizosphere (外根圏)

Fig. An illustration of the rhizosphere A=Amoeba consuming bacteria BL=Energy limited bacteria BU=Non-energy limited bacteria RC=Root derived carbon SR=Sloughed root hair cells F=Fungal hyphae N=Nematode worm

Soil formation process (土壌形成過程)

Stratification (層化)

Podzolization (ポドゾル化)
Leaching (洗脱)
Calcification (石灰集積)
Feralization (鉄アルミナ富化)
Salinization (塩類集積)
Solodization (アルカリ化)
Rocky layer

Fig. Processes of soil formation (Buol 1973)

[water for plant use]

Soil physics (土壌物理学)

Three phase distribution (三相分布)

three phase
Fig. Three-phase distribution