Influence of soil type on juice quality in a vineyard from DO Ca Rioja

Soil plays an important role in wine quality, especially its water holding capacity because it affects the balance between vigour and grape yield. The aim of this work was to study the influence of different soil types on the must quality in a vineyard at DO Ca Rioja. The study was carried out during 2006 and 2007 in a vineyard of eight hectares, located in Oyón in Northern Spain. Four soil types were established according to topography and parent material: deposition (deeper than 110 cm and irregular distribution of organic matter in depth), calcareous red argillite (depth of 85-100 cm, with a heavy clay layer with reddish colour at 85-100 cm), calcareous lutite (depth of 50-100 cm) and finally sandstone (depth of 25-80 cm, and high sand content in depth). Grape samples were collected at 190 grapevines distributed through the whole vineyard for analysing , potential alcohol, total tartaric acid, pH, and K, and anthocyanins concentrations and polyphenols and colour indexes. The influence of soil type on juice quality varied according to the year. In 2006, in the soils with the lower water content (Sandstones) the potential alcohol was the highest (12.92 º), while in 2007, the Red argillite soil (greater water availability) got the greatest potential alcohol (13.72º). The highest acidity was obtained in Depression soil (5.51 g L-1) and was higher in 2007 (5.48 g L-1) than in 2006 (5.07 g L-1). Potassium juice concentration (3068 mg L-1) was higher in the Red argillite soil type due to its higher soil K content, and this caused also the higher pH (3.48) shown in this soil. The anthocyanins content, and polyphenols and colour indexes reached higher values in the Sandstone soil (803 mg L-1, 64 and 24 respectively).