UNDERSTANDING OUR SOILS
Finca Roturas has hillsides with south exposure and a good balance between the quantity of the soil substrate and the quantity of the decomposed limestone rock. This decomposed limestone rock makes easier that the root system penetrates, so that the active limestone for the root system will provide roundness and depth on palate to our wines.
The Ribera del Duero is within the great northern meseta of the Iberian Peninsula, made up of a large, ancient plinth scored and partly covered by Tertiary sediments. Most of the volume of these sediments is made up of more or less lenticular layers of silty or clayey sand, and the alternation of layers, both of limestones and marls and even of calcareous concretions, is a notable feature.
The river basin, formed during the Miocene, displays gently rolling horizontal levels limited by differential erosion, and today converted into peneplain. The relief of the zone ranges between interfluvial zones with peaks of 911 metres, and valleys from 750 to 850 metres in altitude.
The development of the vineyards is conditioned by endless factors, either biotic or abiotic. Within this last category, you can find the physio-chemical properties of the soils.
To fully understand our vineyards, several factors must be acknowledged. These include the climate (minimum, maximum and average temperature throughout the cycle of a vine), the physical structure of the soil (stratums or levels), the evolution of the rocks and their components (clay, slit or sand), the state of alteration of the rock (on granite, for example, the degree of decomposition is decisive) or the terrain’s morphology. Understanding the reasons of our vineyards allow us to have a viticulture of precision. For this purpose, for its correct interpretation, the work of our collaborator Pedro Parra is fundamental.
The tools used by Pedro Parra are the maps he prepares with a scanner of electric conductivity, a technology created for the mining industry related to the clay content on the soil and the trial pits. Trial pits are excavations of 2 metres deep that reveal the different types of levels of the soil. The combination of both allows to work on a scale by delimiting exactly different mini terroirs.
What is the electrical conductivity of the soil? It measures the ability of the soil to conduct electric current in order to use the properties of the salt. In other words, the electrical conductivity measures the concentration of soluble salts in the soil solution. The higher the value, the easier the current moves through the same soil, due to a higher concentration of salts.
The units used to measure the electrical conductivity are dS/m (deciSiemens per metre). This unit of measure is equivalent to mmho/cm, which was used before. With a scanner placed on a quad, the area is scoured to check the resistance of the soil to the electrical current. The result is an analysis of the soil where you can see the conductivity values related to the texture and the structure of the soil in two levels of depth. The high values of electrical conductivity indicate that is a compacted soil or with a high content in clay. The soils with low electrical conductivity are sandy or have little compaction. Besides, the values of the conductivity are related to the permeability of the soil. Maps of permeability are made to see how the water infiltrates the soil when it rains and how the soils retains it so the roots can reach it. All this information allows us to segment the soil and classify the vineyard.
Pedro Parra is the most recognised expert on terroir and soil of South America, with a wide experience in this area. Pedro studied a degree on Precision Agriculture at Montpellier (France) and holds a PhD in terroir from the Paris Centre of Agriculture. While on France, he studied on Burgundy and Bordeaux with highly respected consultants like Michel Claude Girard and Pierre Becheler. He devoted his career to the relationship between wine and terroir. His innovative work was included in Wine Spectator, Decanter and Wine & Spirits Magazine, among others.