Soil and Wine Quality: Chemical attributes

The relationship between soil chemistry and wine quality and individuality is in the main poorly understood. In some quarters there is the belief that soil influences wine character because the vine takes up flavour compounds direct from the soil but this viewpoint is totally unsubstantiated (see, for example, minerals and minerality).

Soil nitrogen is in part an exception to this lack of knowledge. It is clear from Seguin’s work, and that of other European researchers, that the optimum nitrogen supply to the vine is at most only moderate. The optimum supply for red wine production is lower than for white wine because nitrogen deficiency increases berry skin phenolics but also limits the build up of flavour precursors in white grapes (see Peyrot des Gachons et al. and Choné et al.). Vines receiving much nitrogen, unless severely constrained by other factors, have vigorous and leafy growth. This leads readily to excessive shade within the canopy, and thence to poor fruit quality (see canopy microclimate). The effects of nitrogen, water supply, and various other nutritional and environmental factors can to varying degrees reinforce or counteract each other in this regard. The best combination among them is that giving optimum vine balance. Excessive nitrogen fertilization, leading to excessive vigour, can sometimes be problematic in both Old World and New World vineyards. However, this tendency is countered by the more widespread use of grass or cereal cover crops, which can compete with the vine for nitrogen or even cause a deficiency.