Soil spatial variability in the vineyards of La Rioja PDOC (Spain)

Characterisation of soil variables illuminates the influence of the soil on wine quality and other features. The patterns and spatial variability of soil reaction and the content of organic matter, clay, and carbonates of vineyard soils have been investigated throughout the Rioja PDOC area. In total, 212 geo-referenced soil samples were collected from the topsoil (0–30 cm) and subsoil (30–60 cm). Following physical and chemical analysis, the data were subjected to descriptive statistical analysis: minimum, maximum, mean, median, skewness, kurtosis, standard deviation (SD), and coefficients of variation (CVs). Kriging was applied to create distribution maps. Most of these soils are neutral or moderately basic, with high carbonate contents; the clay content is also high but organic matter contents are low. Contents of calcium carbonate and clay are very variable but significant differences were not found between the surface and subsurface pH, carbonate content and clay content; the mean content of organic matter content is low, but somewhat higher in the sub-surface layer, probably because of deep ploughing.