There is a gradual change from a thin humus horizon, not always present, to a dark brown or brown A horizon. There is a sharp change in colour and structure to the C horizon, but sometimes the B horizon rests on rock. A common feature in these soils is a humose B horizon which shows as a darker band where subterranean water seepage deposits organic material above rock or other impermeable horizon. The best conditions for the formation of these soils are found on the drifts derived from the Tertiary basalts of Skye. The loam textures allow free drainage but without the fast leaching rates of the soils of the raised beach and outwash areas, and the basicity of the parent material aids the development of a high biotic activity essential to nutrient recycling.
Brown rankers differ from brown forest soils by their lack of a B horizon and their shallowness.
They occur in an intricate pattern with the brown forest soils. Grazing is the commonest land use since the sward has a high relative grazing value. Steep slopes and rock outcrops restrict most of these soils to LCA Classes 5 and 6, but at a few localities on Skye deep basaltic drifts provide Class 4 arable land. These are found mainly on cultivated areas of glacial till where the combined effects of fine texture and high rainfall result in soils waterlogged during autumn, winter and spring and for long periods in summer. They have no free calcium in their upper mineral horizons which are usually cultivated.