06/05/2025
Soil Order (Soil Science)
1. Alfisols
Etymology: From Alf (aluminum and iron) + sol (soil)
Description: Moderately leached soils with a clay-enriched subsoil (argillic horizon) and relatively high fertility.
Formation Environment: Temperate humid and subhumid regions.
Key Properties:
Argillic (clay) horizon
Base saturation >35%
Vegetation: Hardwood forests, savannas.
Agricultural Use: Very productive; suitable for crops like corn, wheat, and soybeans.
2. Andisols
Etymology: From Ando (Japanese for "black soil") + sol
Description: Soils formed from volcanic ash or other volcanic materials.
Formation Environment: Volcanic regions, often young landscapes.
Key Properties:
High water-holding capacity
High phosphorus retention
Vegetation: Forests, grasslands in volcanic areas.
Agricultural Use: Extremely fertile; ideal for root crops, rice, and coffee.
3. Aridisols
Etymology: From Arid (dry) + sol
Description: Soils of arid regions with limited moisture and biological activity.
Formation Environment: Deserts and semi-arid climates.
Key Properties:
Very low organic matter
May have salic or calcic horizons
Vegetation: Sparse desert vegetation.
Agricultural Use: Limited unless irrigated; used for grazing and specialty crops.
4. Entisols
Etymology: From Ent (recent) + sol
Description: Very young soils with little or no horizon development.
Formation Environment: Steep slopes, floodplains, dunes.
Key Properties:
Minimal profile development
Highly variable
Vegetation: Depends on environment.
Agricultural Use: Varies widely; productive if formed in alluvium.
5. Gelisols
Etymology: From Geli (frozen) + sol
Description: Soils with permafrost within 2 meters of the surface.
Formation Environment: Polar and subpolar regions.
Key Properties:
Presence of permafrost
Cryoturbation (freeze-thaw mixing)
Vegetation: Tundra.
Agricultural Use: Very limited due to freezing and short growing seasons.
6. Histosols
Etymology: From Histos (tissue/organic matter) + sol
Description: Organic soils, formed in water-saturated environments.
Formation Environment: Wetlands, bogs, swamps.
Key Properties:
20–30% organic matter
Poorly drained
Vegetation: Mosses, sedges, shrubs.
Agricultural Use: Drained for crops like vegetables, but prone to subsidence and fires.
7. Inceptisols
Etymology: From Inceptum (beginning) + sol
Description: Young soils with some horizon development.
Formation Environment: Various; common in mountainous or humid regions.
Key Properties:
Weakly developed B horizon
More mature than Entisols
Vegetation: Forests, grasslands.
Agricultural Use: Productive when properly managed.
8. Mollisols
Etymology: From Mollis (soft) + sol
Description: Soils with a thick, dark surface horizon rich in organic matter.
Formation Environment: Grassland ecosystems.
Key Properties:
Mollic epipedon
High base saturation
Vegetation: Prairie grasses.
Agricultural Use: Among the most fertile; excellent for cereal crops.
9. Oxisols
Etymology: From Oxide + sol
Description: Highly weathered tropical soils rich in iron and aluminum oxides.
Formation Environment: Tropical rainforests.
Key Properties:
Low natural fertility
Deep weathering
Vegetation: Dense tropical forests.
Agricultural Use: Needs lime and fertilizer for productivity.
10. Spodosols
Etymology: From Spodos (wood ash) + sol
Description: Acidic soils with subsurface accumulation of organic matter and aluminum/iron.
Formation Environment: Cool, moist climates, especially under conifers.
Key Properties:
Spodic horizon
Leached upper horizon
Vegetation: Coniferous forests.
Agricultural Use: Poor unless heavily amended.
11. Ultisols
Etymology: From Ultimate (last stage of weathering) + sol
Description: Strongly leached, acidic soils with low base saturation.
Formation Environment: Humid tropical/subtropical regions.
Key Properties:
Argillic horizon
Base saturation