Variability of Tempranillo grape quality within the Ribera del Duero do (Spain) and relationships with climatic characteristics

The aim of this research was to evaluate the variability of ripening characteristics of the Tempranillo variety within the Ribera del Duero Designation of Origin (Spain) and it relationships with soil characteristics. This area covers approximately 115 km along the Duero River with elevations from about 700 m to more than 1300 m a.s.l. The climate is temperate with dry or temperate summers in the western portion of the DO area and temperate with a dry summer season in the eastern portion of the DO area. The mean annual temperature ranges between 10.2 and 12.0°C, with mean maximum temperatures around 18.4°C and mean minimum temperatures ranging between 4.5 and 5.0°C. The mean annual precipitation ranges between 413 and 519 mm with the main rainfall periods in April-May and October-November-December.

The main soil types in the Ribera del Duero area are Calcaric Cambisol, Calcic Luvisol, Calcaric Fluvisol, Lithic Leptosol and Calcaric Regosol. The analysis includes the information recorded during the period 2003-2013 in 26 plots throughout the Ribera del Duero DO for parameters such as berry weight (g), sugar content (°Baumé), titratable acidity (AcT) and malic (AcM) acid (gL-1), total (AntT) and extractable (AntE) anthocyanins (mgL-1) and the color index (CI) (in absorbance units). Despite the high variability driven by year to year in climate characteristics, it was possible to indentify the soil and plot characteristics that affect ripening characteristics within the Ribera del Duero. The highest acidity values in grapes were recorded in soils with slightly higher clay and organic matter contents. These plots were located above the river terraces. Additionally, the highest anthocyanins concentrations were also found in plots with the highest organic matter content and with slightly lower soil pH. The effect was greater in the wet years and in those with intermediate characteristics.

The highest anthocyanins and color index values were found in the plots located at lower elevations on the river terraces, while the lower values were recorded in vineyards located on the hillslopes at higher elevation. The results were highly dependent on wet or dry conditions. In dry years high clay and organic matter content gave rise to greater anthocyanin concentrations while in wet years the relationships were the opposite.