The drainage index (DI) is derived from the soil's taxonomic subgroup classification in the US system of Soil Taxonomy and its soil map slope class and reflects the soil's natural wetness condition. The DI ranges from 0 to 99; the higher the index, the more water the soil can supply to plants. The main factors affecting the DI is the depth to the water table and the soil volume available for rooting, soil texture is of minor relevance (Schaetzl et al., 2009).
As the drainage index is based on classification system not used in Europe, it is not applicable under the set frame conditions.