What is typically required for soil to be classified as part of the Eutr great group?

For soil to be classified as part of the Eutr great group, it must be associated with udults, which are a specific classification under the USDA soil taxonomy. This classification is mostly found in soils that have leached away significant amounts of bases but retain a certain level of base saturation, indicating fertility.

Eutr soils are characterized by their positive attributes that typically enhance agriculture and plant growth, such as good nutrient availability and moisture retention. They are often found in humid temperate regions and are classified based on their characteristics and performance. The link to udults is essential because it defines the soil's moisture regime, which includes key features related to the mineral fractions and the organic matter content, directly affecting nutrient cycling and plant nutrition.

The other options do not reflect the primary characteristics required for Eutr classification. While mottles indicate saturation and drainage conditions, they are not a crucial defining feature of Eutr soils. A base saturation lower than 30% would usually categorize a soil as less fertile, passing it out of Eutr classification, indicating low nutrient availability. Soil depth less than 50 cm may affect certain soil classifications but is not a necessary criterion for defining Eutr soils.