Ultisols

{
  "id": "MLC-T-ENV-028957",
  "term": "Ultisols",
  "field": "Environment",
  "definition": "Ultisols are soils that have an argillic or kandic horizon with low base saturation. They may have any soil temperature regime and any soil moisture regime except aridic. There is more precipitation than evapotranspiration at some season, and some water moves through the soils and into a moist or wet substratum. The release of bases by weathering usually is equal to or less than the removal by leaching, and most of the bases commonly are held in the vegetation and the upper few centimeters of the soils. Base saturation in most Ultisols decreases with increasing depth because the vegetation has concentrated the bases at a shallow depth. Cultivation, therefore, is a shifting cultivation unless soil amendments are applied. Ultisols are most extensive in warm, humid climates that have a seasonal deficit of precipitation. They are mainly on Pleistocene or older surfaces. They formed in a very wide variety of parent materials, but very few have many primary minerals that contain bases other than some micas. Some of the few that have a supply of bases are intensively cultivated. Kaolin, gibbsite, and aluminum-interlayered clays are common in the clay fraction. Smectites also may be present if they are in the parent materials. Extractable aluminum normally is high except in the Paleudults and other pale-groups. A calciumdeficient argillic horizon is common in the Ultisols in the United States.",
  "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/ultisols/"
}