The Soil

Vines are grown in several different soil types in the Rioja. There are many, but the most important are three in number: marl, ferrous clays and alluvial soils.

When one enters La Rioja, as does the River Ebro, through the rocky gorge "Las Conchas de Haro", on the left one can see vineyards which grow on yellowish, ochre-coloured soils, on terraces which descend from the Sierra Cantabria to the Ebro. This is the Rioja Alavesa and the soil is marl. Opposite, on one's right, squat, rounded hills and valleys. The valleys are formed by the rivers Oja, Najerilla, Iregua, Leza and Cidacos. On the flat, open land beside these rivers, are vineyards. The soil is alluvial. The reddish slopes which bord these open expanses, are made up largely of ferrous clay soil.

These soils are outlined on the following map. We have tried to imitate the colour of these soils: ochre or light sienna represents marl; the reddish colour, the alluvial soils; we have rendered the ferrous clay soils with brown.

We could even distinguish another ten types of soils, but these are of lesser importance from the viticultural point of view and are not coloured on this map.

The soil-type is distinguished, not only by the colour and the relief of the land - terraced, ridged or flat - but also by its internal structure, clay, sand, rock, stones, etc., so that the development of the root, its growth and expansion, is conditioned by these factors.

Let us imagine how these roots grow in the soil. In yellowish-ochre marl soils, once the "barbado" (or rooted vine) has been planted, it grows roots which progressively extend and deepen until, when they have reached a depth of about one metre, they come across the first disintegrated rock. Only a little lower down, there is compact rock. The roots penetrate easily between the disintegrated rock and look for cracks in the compact rock in order to continue growing downwards. They often find a crack and the root itself, when it thickens inside this crack, increases the size of the cavity. The contact between the roots and the rock does not harm the plant.

In reddish, ferrous clay soils, once the vine has been planted, the development and penetration of the root is slow; this soil is compact, and very clayey. The possibility of their reaching rocky areas is very remote. If however the root encounters rock, this represents a real barrier as usually this rock is very hard and has no cracks.

When the plant rooting is inserted in the alluvial soils of the flat, open plains between the rivers, its roots grow wide and deep, finding loose soil and small, rounded pebbles. However, after descending half a meter, the roots normally come across a white crust which some call "toba", or tufa. This is pure limestone and prevents the roots from passing through due to its hardness, an absence of cracks and the fact that it releases a substance, active limestone, which tends to dry the roots. Therefore the vines do not grow very deep, and are very sensitive to drought and flooding.

Nevertheless, the use of tractors has enabled this crust to be broken during planting and in consequence, the roots reach an undefined depth, finding areas of pebbles and gravel, alternating with loose sandstone.

One may wonder which soils are the best for producing quality wine. It is difficult to give a simple answer, but we understand that the best soil is marl, which covers practically the entire Rioja Alavesa and the municipal districts of Fonzaleche, Sajazarra, Villalba, Briñas, Haro, Briones, Ollauri, Rodezno, Cenicero, Fuenmayor, San Vicente, Abalos, San Asensio and Uruñuela in the Rioja Alta.

However, there are also vineyards on other soils which produce wines of high quality, such as those of Tirgo, Cuzcurrita, Huércanos, Cordovín, Badarán, Ausejo, Tudelilla, Aldeanueva and San Adrián, among many others.

But despite the importance of the soil, there is another, intimately related factor the climate.