Classification
Brown earths have a long history of being a major grouping in most soil classifications. In France they have been included with "sol brun acide", although these soils may tend to have more iron and aluminium in the B horizon, and tend to what, in the British classification, is called a brown podzolic soil. Brown earths are also classified in the German and Austrian soil taxonomy as "Braunerde." Braunerden are widespread and frequently occur on unconsolidated parent sand or loess parent materials. "Parabraunerde" is the classification for a brown earth with an elluvial horison above a slightly argillic, clayey illuvial horizon. This gives rise to a universal division of these, generally brown and well drained soils into the weakly leached brown earths - called cambisols in the international World Reference Base for Soil Resources (WRB); and more leached brown podzolic soils in which there is an orange-brown B horizon, but no pale leached horizon between the A and the B horizons. These are called Umbrisols in the WRB, and are particularly common in western Europe, covering large areas in NW Spain.
Further east in Europe, in more continental climates, the soils show greater leaching of clay and other minerals, and are mapped as luvisols in the WRB. These are rather similar to brown earths, and some other classifications, including the British and French, call these soils argillic brown earths (sol brun lessive), because they have an argillic, i.e. clay-enriched horizon at some depth well below the A horizon. The argillic character is rather weakly expressed in the oceanic climate of the UK, and the differences between brown earths proper (cambic brown earths) and argillic yellow earths are not apparent to the general observer.
Read more about this topic: Brown Earth