Alfisols: Characteristics, Distribution, and Significance

Formation and Characteristics

Alfisols are a soil order characterized by their formation in semi-arid to moist areas, typically under a hardwood forest cover. They possess a clay-enriched subsoil and exhibit relatively high native fertility. The term “Alfisols” is derived from the presence of aluminum (Al) and iron (Fe) in these soils. Alfisols have undergone moderate leaching and possess a base saturation of at least 35%, indicating an abundance of calcium, magnesium, and potassium.

Key Facts

  1. Formation and Characteristics:
    • Alfisols form in semi-arid to moist areas, typically under a hardwood forest cover.
    • They have a clay-enriched subsoil and relatively high native fertility.
    • The name “Alfisols” comes from the combination of aluminum (Al) and iron (Fe) present in these soils.
    • They have undergone moderate leaching and have at least 35% base saturation, meaning they contain relatively abundant calcium, magnesium, and potassium.
  2. Global Distribution:
    • Alfisols occupy approximately 10.1 percent of the global ice-free land area.
    • They are dominant in many areas, such as the Ohio River basin in the United States, southern and unglaciated Western Europe, the Baltic region and central European Russia, the drier parts of Peninsular India, Sudan in Africa, and many parts of South America.
  3. Suborders:
    • Alfisols are divided into five suborders based on specific characteristics:
      • Aqualfs: Saturated with water long enough to cause oxygen depletion, mostly forested.
      • Cryalfs: Occur mainly in high elevations with cold temperatures.
      • Udalfs: Located in humid or subhumid climates, mostly forested.
      • Ustalfs: Found in semiarid climates with wet summers and dry winters.
      • Xeralfs: Located in Mediterranean climates with very dry summers and wet winters.
  4. Productivity and Use:
    • Due to their productivity and abundance, Alfisols are important for food and fiber production.
    • They are widely used in agriculture and forestry and are generally easier to keep fertile than other humid-climate soils.
    • However, Alfisols in Australia and Africa are still deficient in nitrogen and available phosphorus, while those in monsoonal tropical regions tend to acidify when heavily cultivated.

Global Distribution

Alfisols occupy approximately 10.1 percent of the global ice-free land area. They are dominant in various regions, including the Ohio River basin in the United States, southern and unglaciated Western Europe, the Baltic region and central European Russia, the drier parts of Peninsular India, Sudan in Africa, and many parts of South America.

Suborders

Alfisols are divided into five suborders based on specific characteristics:

  1. AqualfsSaturated with water long enough to cause oxygen depletion, mostly forested.
  2. CryalfsOccur mainly in high elevations with cold temperatures.
  3. UdalfsLocated in humid or subhumid climates, mostly forested.
  4. UstalfsFound in semiarid climates with wet summers and dry winters.
  5. XeralfsLocated in Mediterranean climates with very dry summers and wet winters.

Productivity and Use

Alfisols are significant for food and fiber production due to their productivity and abundance. They are widely utilized in agriculture and forestry and are generally easier to maintain fertility compared to other humid-climate soils. However, Alfisols in Australia and Africa are deficient in nitrogen and available phosphorus, while those in monsoonal tropical regions tend to acidify under intensive cultivation.

References

  1. United States Department of Agriculture. (n.d.). Alfisols. Retrieved from https://www.nrcs.usda.gov/conservation-basics/natural-resource-concerns/soils/alfisols
  2. University of Idaho. (n.d.). Alfisols. Retrieved from https://www.uidaho.edu/cals/soil-orders/alfisols
  3. Wikipedia. (2023, September 17). Alfisol. Retrieved from https://en.wikipedia.org/wiki/Alfisol

FAQs

What are Alfisols?

Alfisols are a soil order characterized by their formation in semi-arid to moist areas, typically under a hardwood forest cover. They possess a clay-enriched subsoil and exhibit relatively high native fertility.

Where are Alfisols found?

Alfisols occupy approximately 10.1 percent of the global ice-free land area. They are dominant in various regions, including the Ohio River basin in the United States, southern and unglaciated Western Europe, the Baltic region and central European Russia, the drier parts of Peninsular India, Sudan in Africa, and many parts of South America.

How are Alfisols formed?

Alfisols form through a process called pedogenesis, which involves the physical, chemical, and biological weathering of parent material over time. They are typically formed from sedimentary rocks, such as sandstone and limestone, or from volcanic ash.

What are the characteristics of Alfisols?

Alfisols have a clay-enriched subsoil, known as an argillic horizon, which is formed by the accumulation of clay particles. They also have a relatively high base saturation, meaning they contain an abundance of calcium, magnesium, and potassium. Alfisols are generally well-drained and have a moderate to high water-holding capacity.

What are the different suborders of Alfisols?

Alfisols are divided into five suborders based on specific characteristics:

  • Aqualfs: Saturated with water long enough to cause oxygen depletion, mostly forested.
  • Cryalfs: Occur mainly in high elevations with cold temperatures.
  • Udalfs: Located in humid or subhumid climates, mostly forested.
  • Ustalfs: Found in semiarid climates with wet summers and dry winters.
  • Xeralfs: Located in Mediterranean climates with very dry summers and wet winters.

How are Alfisols used?

Alfisols are widely used for agriculture and forestry due to their productivity and ease of management. They are particularly well-suited for growing crops such as corn, soybeans, and wheat. Alfisols are also used for grazing livestock and for timber production.

What are some of the challenges associated with managing Alfisols?

Alfisols in some regions, such as Australia and Africa, can be deficient in nitrogen and available phosphorus, requiring careful nutrient management to maintain soil fertility. Additionally, Alfisols in monsoonal tropical regions tend to acidify under intensive cultivation, necessitating the application of lime or other amendments to maintain soil pH.

How can Alfisols be managed sustainably?

Sustainable management of Alfisols involves practices that maintain soil health and productivity while minimizing environmental impacts. This includes practices such as crop rotation, cover cropping, and reduced tillage to improve soil structure and organic matter content. Additionally, proper nutrient management and irrigation practices can help prevent nutrient leaching and soil acidification.

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