What percentage of base saturation is required for a mollic horizon?

A mollic horizon is characterized by its rich, dark color, high organic matter content, and a certain degree of base saturation. The requirement for base saturation in a mollic horizon is set at a minimum of 50%. This level indicates that at least half of the cation exchange capacity (CEC) is satisfied by basic cations, such as calcium, magnesium, potassium, and sodium, rather than acidic cations such as hydrogen and aluminum.

This base saturation is important because it reflects the soil's fertility potential and its ability to support healthy plant growth. A mollic horizon with at least 50% base saturation suggests that the soil is well-buffered, helping to maintain a more stable pH and providing essential nutrients to plants. The darker color of mollic horizons is also a visual cue of their organic matter content, which not only aids in nutrient and moisture retention but also enhances microbial activity in the soil.

Though base saturation levels above 50% can contribute to improved soil health, 50% is the minimum threshold required to classify a horizon as mollic. Any percentages below this would not fulfill the criteria for a mollic horizon, which emphasizes that base saturation is central to its definition and characteristics.