In order to classify a soil as umbric, what is the required base saturation percentage?

To classify a soil as umbric, it is essential that its base saturation percentage is less than 50%. This characteristic is a defining feature of umbric horizons, which typically are found in soils with significant organic matter accumulation and a higher level of acidity compared to other similar soil types, such as mollisols.

Umbric soils develop under conditions that allow for leaching and result in a reduced amount of bases (like calcium, magnesium, potassium, and sodium), which contributes to their lower base saturation. In contrast, soils classified with higher base saturation percentages, such as those over 50%, would indicate a different classification, as they align more closely with characteristics of more fertile and less acidic soil types.

Understanding the criteria for base saturation is crucial for soil classification, as it significantly impacts nutrient availability and overall soil health. The umbric classification emphasizes the importance of organic matter content and soil acidity, which are essential factors for various ecological and agricultural considerations.