Bio Bio Valley

Valle del Sur or Southern Valley includes Bio Bio, the most southerly and most extensive wine region in Chile and the Itata sub-region in the north. Over two-thirds of the vineyard acreage in Bio Bio is said to be planted to red grapes, including the Pais. Yumbel and Mulchen, which are becoming more recognized growing areas are sub-zones of Bio Bio.

Bio Bio is more open than Maipo and Rapel to the north, lacking the protection of a high coastal range, so that rainfall is higher and average temperature and sunshine hours are lower.

In the past, the most popular variety had been the Pais, although Moscatel Alejandra is widely grown for basic wine to be consumed within Chile. A significant portion of western vineyards can be found in swampland, capable of producing high quantities of undistinguished wine.

However, research suggests that with drip irrigation and appropriate vine training, some good quality wines from international varieties can be produced here.

Both the Central and Southern valleys have the natural limits of the Andes on the east and the Coastal range on the west. In the latter, there are also extensive areas of vineyards, especially in the sub-zones of Maule and Bio Bio, located further south where the Coastal range is lower.

The latest area to be planted in the south is the Araucania. So far, only about five hectares have been planted here.

Mountainous transversal cordons occasionally break up the Central Valley, which naturally delimits the Maipo and the Rapel sub-zones of Cachapoal and Colchagua. Farther south, the Central Valley widens and there are no barriers of this kind.

In these regions there are six major kinds of soil:

Alluvial Soils: They are best represented in the Maipo Region and are found as far south as the city of Curico’ (Maule region). They are stratified (layered), flat to slightly undulating, medium to very deep, loam (rich soil composed of clay {firm, fine-grained earth}, sand and some organic matter) to clayish-loam, highly fertile.

Low Position Soils of Fine Materials: They are located preferentially near hills and are flat to slightly undulating. They correspond to depression areas where fine materials have accumulated, so their texture is clayish, with poor drainage. Fertility can be low or very high.

Alluvial Colluvial Soils: They are representative of the Maipo region and the Cachapoal sub-region (Rapel). Their texture is loam to clayish-muddy-loam, and they have medium depth, moderate organic material content and good drainage. In certain areas there is some rockiness and sometimes these areas suffer erosion from irrigation.

Soils Derived From Conglomerates (rocks composed of smaller rock particles cemented together in a mass of hardened clay and sand), Breccias (stone composed of fragments of the same rocks) and Tufas: They are found as far south as Colchagua in Rapel and in the Maule. They are flat and slightly undulating. They may be shallow to deep, have clayish-loam texture with good drainage or, on the contrary, drainage may be impeded by the presence of volcanic tufas.

Soils Derived From Volcanic Ash: They are found in the eastern part of the Central Valley from the area level with the city of Talca to the south (Maule). They are flat to slightly undulated with loam to muddy-loam texture. They have good drainage, no erosion and a high organic material content. This kind of soil, which is glacial in origin, now appears south of the city of Curico’ (Maule) and continues toward the south (Bio Bio). It is only interrupted by a cone of boulders at the level of the city of Linares (Maule) which eliminated the old sediments and replaced them with alluvial material, with sand to sandy-loam texture, which is very poor in organic matter. In some places there is erosion. These characteristics extend as far as Nuble River basin (Bio Bio).

Granitoid Type Soils (granite-like, hard igneous rock, composed of quartz, feldspar and mica, crystallized together and varying greatly in texture and color): They generally cover the eastern part of the Coastal range in the Maule and Bio Bio. They make up a very dissected plain, which has formed extensive foothills, alluvial valleys and intermountain valleys. They are medium to deep soils with variable slopes to 30 degrees. They have abundant quartz gravel on the surface and are loam soils. At a certain depth, they have dense, compact clays with moderately slow drainage. They are susceptible to erosion. Organic material is low.