Validation of the viticulture zoning methodology applied to determine the homogenous soil units present on D.O. Ribera de Duero region

The methodology to viticulture zoning developed and proposed by Gómez-Miguel and Sotés (1992) has been studied in order to validate it. This was the main aim of this work, which shows only partial results because data from more vintages will be collected during the next vintages.
The proposed validation is based on the comparison of quality levels of the viticulture products (grapes) grown in different Homogeneous Soil Units (HSU) but classified as the same level of quality. HSUs classified as optimum in Ribera del Duero Denomination of Origin (D.O.) region were chosen for this validation study. The three more important Optimum Units were selected. They represented around of 50% of the global surface of vineyards on the Ribera del Duero viticulture D.O. zone. Five different vineyards in each Unit were chosen. Trying to select the most similar vineyards to reduce variability factors, other selection criteria applied were grape variety, clone, rootstocks, age, training systems and cultural practices.
Three grape samples were collected around of each selected vineyards at the “Technological maturity” stage of the grapes. Different oenological quality parameters were analysed on the collected grapes. After the statistical treatment of the whole analytical data, obtained from grapes collected during two consecutive vintages, some significant results can be pointed out. Among them, it is interesting to note that, in general, variability due to vintage was stronger than that due to the HSU. In a similar way, variability due to vineyards was also significant, and in general, it was bigger than variability due to Units. Furthermore, the whole data showed similar levels of quality after comparing grapes from each HSU studied.
These results seem to validate the proposed methodology. That is, the methodology is valid to determine HSU which can produce grape of a similar quality, and then it can be applied to the correct or appropriate use of the agriculture medium.