Pedogenesis: Stages, Factors, and Global Soil Classification

Stages of Soil Evolution

• Initial Stage (Born): The substrate begins to decompose, and particles deposit.
• Development Stage: The soil profile develops, increasing in thickness and distinct characteristics.
• Maturity Stage: Reaching the climax of soil evolution and profile differentiation.
• Impairment Stage: Environmental conditions cause destruction or degradation of the soil structure.
• Death Stage: When the soil is completely eroded and disappears.

Key Factors Influencing Soil Formation

• Substrate (Parent Material): The source material, often originating from underground rock or sediment.
• Climate: Rainfall intensity and duration can cause leaching, impoverishing surface horizons.
• Vegetation (Biota): Specific plant types enrich the soil or provide protection against erosion.
• Time (Age): Soil formation is a slow process, taking many centuries to develop a significant thickness.
• Relief (Topography): Flat terrain favors waterlogging, while rugged terrain leads to greater leaching and erosion risk, especially on steep slopes.
• Human Influence (Anthropogenic Factor): Human actions often act as a negative factor in soil health and stability.

Global Classification of Soil Types

Initial Soils (Lack Distinct Horizons)

• Fluvisol: Found in areas receiving inputs of sediments (alluvial deposits).
• Leptosol (Litosol): Formed by weathering of rock (shallow, rocky soil).
• Regosol: Formed on unconsolidated sediments or sedimentary rock (mineral soil).

Poorly Differentiated Soils (Limited Development)

• Aleptosol: Found primarily on steep slopes.
• Ranker: Developed on siliceous parent materials.
• Rendzina: Developed on calcareous parent materials.
• Xerosol: Soil poor in organic matter (often associated with arid climates).
• Solonchak (Saline Soil): Aridity causes salt crusts to appear on the surface.
• Vertisol: Containing a mixture of expansive clay minerals and organic matter.
• Arenosol: Developed from sandy parent material.
• Andosol: Originated from volcanic rock or ash.

Fully Formed Soils (Clearly Differentiated Horizons)

• Cambisol (Brunisol): Characterized by parent material plus organic and iron compounds.
• Wet Cambisol: Found specifically in oceanic climates.
• Southern Cambisol: Found in Mediterranean or internal climates.
• Calcic Cambisol (Limestone Soil): Associated with limestone regions.
• Luvisol (Red Soil): Rich in clay and iron oxides.
• Histosol: Overlying moist organic matter (Peat soil).

Deteriorating Soils (Leached and Washed)

• Podzol: Highly leached due to large amounts of infiltrating water, resulting in distinct bleached horizons.