Sombric Horizon

{
  "id": "MLC-T-ENV-026143",
  "term": "Sombric Horizon",
  "field": "Environment",
  "definition": "A sombric horizon (F. sombre, dark) is a subsurface horizon in mineral soils that has formed under free drainage. It contains illuvial humus that is neither associated with aluminum, as is the humus in the spodic horizon, nor dispersed by sodium, as is common in the natric horizon. Consequently, the sombric horizon does not have the high cation-exchange capacity in its clay that characterizes a spodic horizon and does not have the high base saturation of a natric horizon. It does not underlie an albic horizon.",
  "references": [
    "USDA Natural Resources Conservation Service Soil Taxonomy: A Basic System of Soil Classification for Making and Interpreting Soil Surveys (1999)"
  ],
  "url": "https://mlchart.com/terminology/environment/sombric-horizon/"
}