For a soil to be classified as a spodosol, what must it typically contain?

For a soil to be classified as a spodosol, it must typically contain leached horizons with organic matter. This classification is largely characterized by the presence of a distinct horizon called the spodic horizon, which is commonly found in cool, moist climates where there is significant leaching of bases and the accumulation of organic matter, often in the form of illuvial humus and aluminum oxides.

The process of podzolization, which occurs in spodosols, results in the leaching of iron and aluminum from the upper layers of the soil and their subsequent accumulation in the lower horizons. This characteristic horizon is typically lighter in color due to the loss of minerals and is a defining feature of spodosols. Thus, the presence of these leached horizons enriched with organic materials is essential for the classification of a soil as a spodosol.

High base saturation, high iron content, and silty texture do not define spodosols as strictly. High base saturation is more characteristic of other soil types, high iron content can be present in various soil orders, and silty texture is not a defining trait of spodosols. Thus, it is the organic matter-rich leached horizons that solidify the classification of spodosols.