Soils in Alsace

Soil classification

Soil is the common name for the loose material laying on top of the bedrock. If we exclude purely organogenic soils, such as peat, soil material consists of smaller particles that have come of rock. Thereafter, the soil material has been deposited where we now find it. One can classify soils in many ways, one is according to deposition mechanism.

Alluvial soils have been deposited from running water. Depending on the waters velocity and the size of the particles, some will follow the water, others will tumble on the streambed while others will loose their speed and come to rest. As conditions vary, the deposition rates will vary and consequently alluvial soils will often exhibit distinct layers. Most soils in the vinyards of Alsace are alluvial, but one can distinguish three categories; the hillsides (most terroirs), the river beds (e.g. the lieux-dits Clos des Capucins, Herrenweg and Harth) and parts of the Alsace plain.

Colluvial soils are formed when soil particle slowly move downhill by gravity. Examples of terroirs where colluvium are important are on Grands Crus Schoenenbourg, Brand and Steingrubler.

Sea sediments are deposited in almost stagnant water, such as giant river beds. In this environment, even the smallest particles may form sediment. The result is deep, heavy, and fertile soils. The Alsace plain is one example.

The soil particles are divides into specific fractions:
Block Block Bloc >600 mm
Sten Pepple Pierre 60-600 mm
Grus Gravel Gravière 2-60 mm
Sand Sand Sable 0.063-2 mm
Silt Silt/Loam Vase 0.002-0.063 mm
Ler Clay Argile <0.002 mm

One should distinguish between clay particles (defines by size), clay minerals (defined by molecular structure) and clay soils (defined as soils with more than 30% clay particles).