Soil-related terroir factors: a review

A "terroir" is a cultivated ecosystem in which the vine interacts with the soil and the climate. The soil influences vine development and grape ripening through soil temperature, water supply and mineral supply. Soil temperature has a significant effect on vine phenology. Limited water supply to the vines restricts shoot and berry growth, which is critical for reaching a suitable grape composition to produce high-quality red wines. Secondary metabolites, like polyphenols (anthocyanins, tannins) and aroma compounds or their precursors, are impacted in particular by vine water status. Among nutrients vines pick up from the soil, nitrogen plays a key role. Nitrogen influences vine vigor, yield, berry size and grape composition. Low nitrogen supply stimulates the synthesis of polyphenols, while it can negatively impact certain aroma compounds in grapes and wines. Over the past decades, tools have been developed to quantify terroir parameters. Vine water status can be assessed by means of carbon isotope discrimination measured on grape sugar (so-called delta C-13). Vine nitrogen status can be assessed with the measurement of Yeast Available Nitrogen (YAN). In this way, terroir parameters can not only be measured but also mapped. Ideally, vineyards should be established in areas where soil temperature (relative to air temperature), soil water holding capacity (relative to rainfall and potential evapotranspiration) and soil nitrogen availability are optimum for the type of wine which is intended to be produced. Terroir expression can, however, be optimized by choosing appropriate plant material, and via vineyard floor management, fertilization and other management techniques.