The fundamental types of soils to be found in the vineyards of the Rioja region are:
- Calcareus clay
- Ferrous clay
Each one of these types supposes a different depth structure, which influences the contour of these tracts of land, the way in which the vineyards are worked and the possibilities of being able to build underground wine cellars.
The calcareous – clay soils are comprised of alternating layers of loose clay soil and horizontal layers of sandstone, fissured to a great extent (diaclassas), through which the roots of the grapevines can penetrate. There lands are apt for building underground wine cellars.The amount of active limestone varies only alightly throughout these layers, being of 8% – 10%.
The ferrous – clay soils are found on lands wich are rich in clay, having deep, rocky layers which are neither very thick nor horizontal, and which are of the hard, calcareous type. The active limestone is limited in quanttity, varying between 2% and 3%. These lands are somewhat appropiate for caves for storing wines.
The alluvial soils have, as a peculiar characteristic, a thin crust of pure limestone, formed through the precipitation of carbonates carried by rain water. On the surface and below these soils, there are a great deal of pebbles. Previously, these soils were not apt for vineyards, as the active limestone in said crust can be of up to 20%. Nowadays, they are used for vineyards thanks to powerful, modern groundbreaking equipment. These lands are not apt for the building of underground wine cellars.
© Manuel Ruiz Hernández, 1999