Soil Orders and Classification Flashcards

Entisols

• Least weathered soil type with minimal horizon development.
• Formed from the youngest parent materials like landslide deposits or freshly disturbed forest areas.
• Characterized by the absence of distinct B horizon; typically features only an A horizon.
• Not specific to any biome, making it one of the most common soil types.

Inceptisols

• Mid-level weathered soils with slight horizon development.
• Possess a dark organic layer called an umbric layer but contain minimal organic material.
• Distributed widely across various landscapes.

Andisols

• Most weathered soil among low weathering types, primarily formed from volcanic lava.
• Commonly located around the Pacific Rim, notable in regions like Hawaii and Japan.
• Exhibits unique properties, including high water-holding capacity and the ability to make phosphorus unavailable to plants.

Gelisols

• Less weathered soils characterized by the presence of permafrost.
• Formed from organic matter and contain no distinct B horizon.
• Rich in organic matter yet hold minimal minerals; found in high-latitude polar regions.

Histosols

• Soil type rich in organic material, typically found in wetlands, peatlands, swamps, and marshes.
• Features a thick O horizon that exceeds 40 cm and comprises at least 20-30% organic matter by weight.
• Contains no bedrock beneath the surface.

Aridisols

• Intermediate weathering soil type found in arid and desert regions.
• Characterized by low carbon content and indistinguishable horizons due to slow soil development.
• Limited vegetative cover results from minimal rainfall, hindering chemical weathering.

Vertisols

• Intermediate weathering soil type associated with high base status and high activity clays.
• Typically found in wetter areas; exhibits significant shrinkage and cracking during dry seasons.
• High clay content distinguishes this soil type, contrasting with aridisols.

Alfisols

• More advanced weathering soil, often referred to as "catch-all" soil, prevalent in semi-arid to humid ecosystems.
• Moderately leached with high native fertility; generally mildly acidic and features clay accumulation.
• Primarily found in temperate humid and subhumid regions, contributing to productive agriculture.

Mollisols

• Advanced weathering soils associated with grassland ecosystems.
• Distinguished by a thick, dark surface horizon rich in organic matter, often found in prairie regions like the Great Plains in the U.S.
• Highly productive agricultural soils, integral to farming practices, even after abandoning agriculture.

Spodosols

• Most weathered and highly leached soil type, typically found in cool, wet climates with sandy textures.
• Extremely acidic and primarily located in coniferous forests.
• Characterized by a light-colored E horizon above a reddish-brown spodic horizon formed in coarse-textured parent material.

Ultisols

• Most weathered soil type known for strong leaching and acidity.
• Often found in humid temperate and tropical regions, typically located on older, stable landscapes.
• Reddish hue due to iron content; characterized by a highly weathered B horizon with relatively low native fertility.

Oxisols

• Highly weathered soils found in intertropical regions, marked by a distinguished red color.
• Composed of minerals rich in iron and aluminum oxides, resulting in extremely low native fertility.
• Characterized by very low nutrient reserves and high phosphorus retention, which limits agricultural usefulness.