Soil Colour

soil colour, a term normally referring to the surface colour of a soil although it may also be applied to various layers or horizons in a soil profile. Some viticultural folklore associates red wine with red soils, and white wines with white or grey soils. However, topsoil colour is very heterogeneous, as is the spatial distribution of soil types within vineyards potentially planted to a single variety. So any support for such a relationship is at best circumstantial.

Colour can affect soil temperature, and that of the air immediately above it. Dark-coloured soils or rocks absorb much of the incoming sunlight energy and convert it to heat. Therefore, whereas they reflect less light than light-coloured soils, they radiate more heat at night and when the sun is shaded. This may be especially beneficial in cool climates. Other examples of the exploitation of these thermal characteristics include the vineyards of Deidesheim in the pfalz region of Germany, where black basalt rock is mined and spread on the vineyards to help produce wines of unusual sweetness. Fragmented dark grey slate helps Riesling to ripen in the otherwise very cool mosel. Dark-coloured schist soils are reportedly the only ones on which grapes can be ripened at the extreme northern limit of viticulture in belgium. At the other extreme, the exceedingly reflective white albariza soils of jerez in southern Spain produce the best (white) grapes for sherry in a very hot climate, which would seem counter-intuitive.